Obesity and thyroid cancer: unraveling the connection through a systematic review and meta-analysis of cohort studies

Background

The relationship between adiposity indicators and thyroid cancer (TC) risk has garnered increasing attention due to the rising prevalence of obesity and its potential impact on cancer incidence. We conducted a comprehensive meta-analysis to investigate this association across various effect measures.

Method

Until July 2022, a comprehensive search of databases was conducted to identify cohort studies that assessed the association between adiposity and the development of TC. Meta-analysis was performed using random effects models. Subgroup analyses were conducted to explore heterogeneity. Publication bias was assessed using Begg's tests.

Results

A systematic literature search identified 27 eligible studies reporting odds ratios (OR), relative risks (RR), or hazard ratios (HR) as effect measures. Pooling the studies irrespective of the effect measure, a significant positive association between adiposity indicators and TC risk was observed, yielding an effect estimate of 1.16 (95% CI 1.12-1.21). The combined effect estimate for OR/RR studies was 1.10 (95%CI 1.04-1.17), while HR studies yielded an effect estimate of 1.20 (95%CI 1.13-1.26). Subgroup analyses revealed associations across different age groups, obesity indices, and regions, with some variations based on effect measure. Meta-regression identified follow-up duration as a confounding factor only in HR studies.

Conclusion

The synthesis of 27 studies with diverse designs and populations underscores a robust positive association between adiposity and TC risk, providing compelling evidence for the potential role of increased adiposity in TC development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01425-3.

Prevalence of cervical intraepithelial lesions and associated factors among women attending a cervical cancer clinic in Western Uganda; results based on Pap smear cytology

Introduction

There are high incidence and mortality rates of cervical cancer among females in East Africa. This is exacerbated by limited up-to-date data on premalignant lesions and associated factors in this setting. In this study, we determined the prevalence of cervical intraepithelial lesions and associated factors among women attending the Mbarara Regional Referral Hospital cervical cancer clinic in Southwestern Uganda.

Methods

In this cross-sectional study, 364 participants were recruited from among women attending the Mbarara Regional Referral Hospital cervical cancer clinic from 1 April to 30 June 2023. On consent, the study nurse collected demographic data and Pap smears, which were microscopically examined and reported by a laboratory scientist and a pathologist following the Bethesda grading system (2014). Statistical analyses were done in STATA version 17, using proportions, Chi-square, bivariate, and multivariate logistic regression analysis to determine associated factors at ⩽0.05 significance level.

Results

The mean age of participants was 41.9 years. A third of all study participants (37.6%, 132/351) were contraceptive users, mostly hormonal contraceptives (87.1%, 115/132). Almost 88% (307/351) had an unknown Human Papilloma Virus status. The prevalence of cervical intraepithelial lesions among our study participants was 6.6% (23/351), of which 73.9% (17/23) were low-grade squamous intraepithelial lesions. More than half (9/17, 52.9%) of low-grade squamous intraepithelial lesions were active hormonal contraceptive users. Use of hormonal contraceptives (OR: 3.032, p: 0.0253), use of intrauterine devices (OR: 6.284, p: 0.039), and any family history of cervical cancer (OR: 4.144, p: 0.049) were significantly associated with cervical intraepithelial lesions.

Conclusion

The prevalence of cervical intraepithelial lesions was 6.6%, lower than global estimates. Use of hormonal and intrauterine device contraceptives, as well as family history of cervical cancer, were significantly associated with cervical intraepithelial lesions among our study population. Prospective studies are recommended to further understand associations between different types of intrauterine devices and hormonal contraceptives, and cervical lesions.

The underestimated impact of excess body weight on colorectal cancer risk: Evidence from the UK Biobank cohort

BACKGROUND

The association between excess weight and colorectal cancer (CRC) risk may have been underestimated due to potential weight loss during pre-clinical sojourn time of CRC. We aimed to investigate this association and the corresponding population attributable fraction (PAF), accounting for prediagnostic weight loss.

METHODS

Data from the UK Biobank prospective cohort were used. Multivariable adjusted hazard ratios (HR) and their 95% confidence intervals (CI) for various periods of follow-up and the corresponding PAF of excess weight were calculated.

RESULTS

During a median of 10.0 years of follow-up, of 453,049 participants, 4794 developed CRC. The excess weight-CRC association became substantially stronger with including increasing lengths of follow-up in the analyses and further excluding the initial years of follow-up. HRs (95% CIs) for overweight and obesity were 1.06 (0.97-1.16) and 1.14 (1.03-1.26) after 7 years of follow-up, 1.13 (1.05-1.21) and 1.23 (1.14-1.33) when including complete follow-up length, and 1.26 (1.12-1.43) and 1.42 (1.24-1.63) when excluding the initial 7 years of follow-up. The corresponding PAFs of excess weight were estimated as 6.8%, 11.3%, and 19.0%, respectively.

CONCLUSIONS

Comprehensive consideration of the potential effect of prediagnostic weight loss discloses a much stronger impact of excess body weight on CRC risk than previously assumed.

Anthropometric indicators of adiposity and risk of primary liver cancer: A systematic review and dose-response meta-analysis

BACKGROUND AND AIMS

Adiposity is associated with an increased risk of primary liver cancer (PLC). As the most commonly used indicator of adiposity, the body mass index (BMI) has been questioned for its limitations in reflecting visceral fat. This study aimed to investigate the role of different anthropometric indicators in identifying the risk of PLC by accounting for potential non-linear associations.

METHODS

Systematic searches were conducted in the PubMed, Embase, Cochrane Library, Sinomed, Web of Science, and CNKI databases. Hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs) were used to assess the pooled risk. The dose-response relationship was assessed using a restricted cubic spline model.

RESULTS

Sixty-nine studies involving more than 30 million participants were included in the final analysis. Regardless of the indicator used, adiposity was strongly associated with an increased risk of PLC. When comparing the HRs per 1-standard deviation increment across indicators of adiposity, the association was strongest for waist-to-height ratio (WHtR) (HR = 1.39), followed by waist-to-hip ratio (WHR) (HR = 1.22), BMI (HR = 1.13), waist circumference (WC) (HR = 1.12), and hip circumference (HC) (HR = 1.12). A strong non-linear association was observed between each anthropometric parameter and the risk of PLC, regardless of whether the original or decentralised value was used. The positive association between WC and PLC risk remained substantial after adjusting for BMI. The incidence of PLC was higher with central adiposity (52.89 per 100,000 person-years, 95% CI = 50.33-55.44) than general adiposity (39.01 per 100,000 person-years, 95% CI = 37.26-40.75).

CONCLUSION

Central adiposity seems to contribute more to the development of PLC than general adiposity. A larger WC, independent of BMI, was strongly associated with the risk of PLC and might be a more promising predictive indicator than BMI.

Association between obesity and cervical intraepithelial neoplasia: results from a case control study in south western Uganda

BACKGROUND

Though obesity has been said to be associated with a number of malignancies including cervical cancer, its association with cervical intraepithelial neoplasia (CIN) is still a contentious issue. This study was designed to determining the prevalence and association between obesity and CIN.

METHODS

This was an unmatched case control study, involving women with cervical intraepithelial neoplasia (cases) and those negative for intraepithelial lesions or malignancy (controls) at the cervical cancer clinic of Mbarara Regional Referral Hospital, in south-western Uganda, between April and November 2022. Cases and controls provided written informed consent and were recruited in a ratio of 1:1. Cases were identified by visual inspection with acetic acid (VIA) and subsequent confirmation with cytology and/or histology. Demographic information was collected using an enrolment form and height, weight and waist circumference were recorded. We calculated body mass index (BMI) and identified obese women as those with body mass index of ≥ 30 kg/m² from both case and control groups. Central obesity was defined as waist: height ration of ≥ 0.5. Data was analysed using STATA version 17. Categorical variables were analysed using proportions, chi-square and logistic regression analysis to determine association between obesity and CIN. Our level of statistical significance was set at ≤ 0.05.

RESULTS

The prevalence of general and central obesity among cases was 25.5% (24/94) and 0% (0/94) respectively while the prevalence of general and central obesity among controls was 33.3% (37/111) and 0% (0/111) respectively. There was an increased prevalence of general obesity among women with low grade squamous intraepithelial lesions (LSIL). However, there was no statistically significant association between general obesity and CIN. Factors associated with general obesity included residing in Mbarara city (AOR 2.156, 95%CI 1.085-4.282, P-value 0.028), age group of 31-45 years (AOR 2.421, 95%CI 1.577-9.705, P-value 0.003) and ≥ 46 years (AOR 1.971, 95%CI 1.022-11.157, P-value 0.046).

CONCLUSION

We observed an increased prevalence of general obesity among women with LSIL. However, there was no association between obesity and CIN. Factors associated with general obesity included residing in Mbarara city, and being in the age groups of 31-40 and ≥ 46 years. This highlights the need to rethink management of CIN to control other non-communicable diseases that could arise due to general obesity.

Women with obesity participate less in cervical cancer screening and are more likely to have unsatisfactory smears: Results from a nationwide Danish cohort study

Some studies found an association between obesity and increased cervical cancer risk, but potential mechanisms are unknown. In this nationwide register-based cohort study, we investigated the association between overweight/obesity and cervical cancer screening participation and risk of unsatisfactory smears. The study population was identified in the Danish Medical Birth Registry. We included 342,526 women aged 23-49 years with pre-pregnancy body mass index (BMI) registered during 2004-2013. Screening participation and unsatisfactory smears during up to four years after child birth were identified in a nationwide pathology register. We used absolute risk regression to estimate the relative absolute risk (RAR) with 95% confidence intervals (CIs) of screening participation according to BMI, adjusted for age, calendar year, sociodemographic characteristics, parity and previous high-grade cervical intraepithelial neoplasia. Among those who were screened (n = 295,482), we used log-binomial regression to investigate the relative risk (RR) of an unsatisfactory smear according to BMI, adjusted for age, year, parity, oral contraceptive use and pathology department. A lower proportion of obese women (79.3%) than women of normal weight (85.8%) were screened, and obese women had lower adjusted probability of being screened than women of normal weight (RAR_adjusted = 0.94, 95% CI, 0.93-0.95). A higher proportion of obese women (2.4%) than women of normal weight (1.7%) had an unsatisfactory smear, and this association remained after adjustments (RR_adjusted = 1.28, 95% CI, 1.19-1.38). In conclusion, women with obesity were less likely to participate in cervical cancer screening and more likely to have an unsatisfactory smear than women of normal weight.

Body Mass Index and Thyroid Cancer Risk: A Pooled Analysis of Half a Million Men and Women in the Asia Cohort Consortium

Background: Although previous meta-analyses have suggested a dose-response relationship between body mass index (BMI) and thyroid cancer risk, limited evidence has been presented about Asian populations. To assess this association among Asian populations, where underweight is more prevalent than in other regions, a pooled analysis from the Asia Cohort Consortium was conducted. Methods: Baseline height and weight were measured in five cohorts and self-reported in eight cohorts. Thyroid cancer incidence was ascertained by linkage to local cancer registries. Cohorts were treated as a stratum in the Cox proportional hazard model to estimate the pooled hazard ratios (HRs) and corresponding confidence intervals (CIs) from the estimates for each cohort. All analyses were stratified by sex. Results: A total of 538,857 men and women from 13 cohorts from mainland China, Korea, Japan, and Singapore were included in the analysis. During a mean of 15.1 years of follow-up, 1132 thyroid cancer cases were ascertained. Using a BMI of 18.5-22.9 kg/m² as a reference, an elevated risk of thyroid cancer was observed for groups with a BMI between 25 and 29.9 kg/m² (HR: 1.31, [CI: 0.95-1.80]) and a BMI of 30 kg/m² and greater (HR: 1.84, [CI: 0.89-3.81]) in men. Thyroid cancer risk was elevated in women with a BMI of 23-24.9 kg/m² (HR: 1.26, [CI: 1.07-1.48]). The HRs for 5-U increment of BMI showed a linear association among men (HR: 1.25, [CI 1.10-1.55]) but not among women (HR: 1.07, [CI: 0.97-1.18]). Although the overall thyroid cancer risk was lower among underweight men and women, the papillary cancer risk may be elevated among underweight men (HR: 2.24, [CI: 0.75-6.66]). Conclusion: While higher BMI is associated with an elevated risk of thyroid cancer in both men and women, the association of underweight BMI may differ by sex and histological subtype.

Impact of Body Mass Index on Local Recurrence according to Intrinsic Subtype Approximation in Korean Women with Early Stage Invasive Breast Cancer Receiving Contemporary Treatments

Purpose: We investigated the prognostic impact of body mass index (BMI) on local recurrence (LR) according to intrinsic subtype in Korean women with early stage, invasive breast cancer.

Materials and methods: We included 907 patients with pathological stage T1-2 and N0-1 breast cancer who underwent curative surgery between 2007 and 2012. Systemic treatments were administered in 876 patients (96.6%). In total, 701 patients (77.3%) received radiotherapy. Intrinsic subtypes were determined using immunohistochemical staining results.

Results: During the median follow-up period of 72 months, LR as the first failure occurred in 29 patients, including 24 patients with isolated LR. The 5-year cumulative incidence rate of LR was 3.2% among all patients. In the luminal A subtype, a BMI of <18.5 kg/m² was an independent risk factor for LR, as determined by a competing-risk regression model (relative risk, 3.33; p = 0.041). Severely obese patients (BMI >30 kg/m²) with the triple negative subtype had an increased risk of LR (relative risk, 3.81; p = 0.048).

Conclusion: The present study identified traditionally underestimated risk groups for LR. BMI may diversely influence the rate of LR across intrinsic subtypes in Korean patients with breast cancer.

Cigarette Smoking and Estrogen-Related Cancer

Cigarette smoking is a known cause of many cancers, yet epidemiologic studies have found protective associations with the risk of four "estrogen-related" malignancies: endometrial cancer, endometrioid and clear cell ovarian cancers, and thyroid cancer. This review considers epidemiologic and biological aspects of these associations, focusing particularly on estrogen signaling, and contrasts them with those for breast cancer, another estrogen-related malignancy. The observational findings regarding the inverse associations are consistent and remain after adjustment for possible confounding factors. In general, women who smoke do not have lower circulating estrogen levels than nonsmokers, eliminating one possible explanation for reduced risks of these malignancies. For endometrial and endometrioid ovarian cancer, the negative associations could plausibly be explained by interference with signaling through the estrogen receptor α. However, this is unlikely to explain the lower risks of thyroid and clear cell ovarian cancers. For thyroid cancer, an anti-inflammatory effect of nicotine and reduced TSH levels from smoking have been proposed explanations for the inverse association, but both lack convincing evidence. While the overall impact of cigarette smoking is overwhelmingly negative, protective associations such as those discussed here can provide potential clues to disease etiology, treatment, and prevention.

Morbid Obesity and Thyroid Cancer Rate. A Review of Literature

In the past three decades, several recent studies have analyzed the alarming increase of obesity worldwide, and it has been well established that the risk of many types of malignancies is increased in obese individuals; in the same period, thyroid cancer has become the fastest growing cancer of all malignancies. We investigated the current literature to underline the presence of a connection between excess body weight or Body Mass Index (BMI) and risk of thyroid cancer. Previous studies stated that the contraposition between adipocytes and adipose-resident immune cells enhances immune cell production of multiple pro-inflammatory factors with subsequent induction of hyperlipidemia and vascular injury; these factors are all associated with oxidative stress and cancer development and/or progression. Moreover, recent studies made clear the mitogenic and tumorigenic action of insulin, carried out through the stimulation of mitogen-activated protein kinase (MAPK) and phosphoinositide-3 kinase/AKT (PI3K/AKT) pathways, which is correlated to the hyperinsulinemia and hyperglycemia found in obese population. Our findings suggest that obesity and excess body weight are related to an increased risk of thyroid cancer and that the mechanisms that combine overweight with this cancer should be searched for in the adipokine pathways and chronic inflammation onset.

Obesity and the prevention of thyroid cancer: Impact of body mass index and weight change on developing thyroid cancer - Pooled results of 24 million cohorts

BACKGROUND

Body weight may be a modifiable risk factor predisposing to different cancers. To establish a potential impact of weight change on thyroid cancer risk, we conducted a meta-analysis to evaluate the effect of body mass index (BMI) and weight change over time as a risk of developing thyroid cancer (TC).

METHODS

A systematic search was performed up to February 25, 2020. Pooled relative risk (RR) were estimated using fixed and random models. Heterogeneity between articles was examined using Q-test and I² index. Evaluation of publication bias was conducted with Egger's regression test.

RESULTS

A total of 31 studies including 24,489,477 cohorts were eligible. Pooled analysis revealed that normal and underweight cohorts were associated with a decreased risk of TC (RR = 0.68, 95%CI = 0.65-0.71, p < 0.001) and (RR = 0.92, 95%CI = 0.91-0.93, p < 0.001), respectively. In contrast, overweight and obese cohorts were more likely to develop TC (RR = 1.26, 95%CI = 1.24-1.28, p < 0.001 and RR = 1.50, 95%CI = 1.45-1.55, p < 0.001, respectively). Obesity was associated with higher risk of developing TC among women (RR = 1.29, 95%CI = 1.14-1.46, p < 0.001), but not men (RR = 1.25, 95%CI = 0.97-1.62, p = 0.08). Furthermore, weight gain increased the risk of developing TC (RR = 1.18, 95%CI = 1.14-1.22, p < 0.001), while weight loss decreased the risk (RR = 0.89, 95%CI = 0.85-0.93, p < 0.001). Results showed similar trends of weight change effect in both males and females.

CONCLUSIONS

Obesity is associated with higher risk of developing TC in women. However, maintaining a healthy weight is associated with reduced risk of TC in both women and men. Shifting our practice to include weight control strategies will help lead to cancer prevention.

Obesity and breast cancer risk for pre- and postmenopausal women among over 6 million Korean women

PURPOSE

To examine the association between obesity measured by body mass index (BMI) and waist circumference (WC) according to menopausal status in Korean women.

METHODS

We identified 6,467,388 women, using the Korean National Health Insurance System Cohort. Cox-proportional hazard models were used to generate adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for breast cancer risk in relation to BMI and WC.

RESULTS

In postmenopausal women, the risk of breast cancer increased with BMI. Compared to women with a BMI of 18.5-23 kg/m two, the risk of invasive breast cancer was lower in patients with BMI < 18.5 (aHR 0.82, 95% CI 0.75-0.89), while it increased linearly in those with BMI 23-25 (1.11, 1.08-1.14), BMI 25-30 (1.28, 1.25-1.32), and BMI ≥ 30 (1.54,1.47-1.62). In contrast, the risk of breast cancer decreased with BMI in premenopausal women. Compared to women with a BMI of 18.5-23, the risk of IBC was similar in those with a BMI < 18.5 (1.02, 0.94-1.11) and BMI 23-25 (1.01, 0.97-1.05), but was significantly lower in those with a BMI 25-30 (0.95, 0.91-0.98) and BMI ≥ 30 (0.90, 0.82-0.98). A relative increase with BMI was less profound for carcinoma in situ in postmenopausal women, and a relative decrease was more profound in premenopausal women. An analysis using WC showed almost identical results.

CONCLUSIONS

There was a positive relationship between obesity and breast cancer in postmenopausal women, and an inverse association in premenopausal women.

The effect of visceral fat on the hemodilution effect of serum carcinoembryonic antigen in Korean population

OBJECTIVE

To investigate the relationship between visceral fat and the hemodilution effect of carcinoembryonic antigen in both sexes.

METHODS

A total of 15,340 females and 20,024 males who visited the health promotion center at Chung-Ang University Hospital from 2011 to 2014 were retrospectively collected. Correlation analysis and chi-square test for linear by linear association were used to determine the correlation between carcinoembryonic antigen concentration, carcinoembryonic antigen mass and visceral fat. Multivariable linear regression analysis was used to calculate the mean of carcinoembryonic antigen concentration and the mean of carcinoembryonic antigen mass, reflecting age, aspartate aminotransferase, alanine aminotransferase, creatinine, body fat percentage, body mass index, lean body mass and waist circumference as confounding variables.

RESULTS

Higher body mass index was related with lower carcinoembryonic antigen concentration in men (r = -0.019, P = 0.019), but higher carcinoembryonic antigen concentration in women (r = 0.084, P<0.001). Average of waist circumference for male is greater than that of female (P<0.01). Average of body fat percentage for male is lesser than that of female (P<0.01). Male lean body mass mean is larger than that of women (P<0.01). Increased waist circumference was significantly associated with higher carcinoembryonic antigen mass in both female and male (P<0.001 for trend). Postmenopausal women might be more likely to have increased carcinoembryonic antigen mass and carcinoembryonic antigen concentration (P<0.001 for trend).

CONCLUSIONS

This study suggests that visceral fat may increase total amount of CEA in the body. Visceral fat should be taken into account when evaluating serum CEA levels in both sexes.

World Cancer Research Fund International: Continuous Update Project-systematic literature review and meta-analysis of observational cohort studies on physical activity, sedentary behavior, adiposity, and weight change and breast cancer risk

PURPOSE

The purpose of the present study was to systematically review the complex associations between energy balance-related factors and breast cancer risk, for which previous evidence has suggested different associations in the life course of women and by hormone receptor (HR) status of the tumor.

METHODS

Relevant publications on adulthood physical activity, sedentary behavior, body mass index (BMI), waist and hip circumferences, waist-to-hip ratio, and weight change and pre- and postmenopausal breast cancer risk were identified in PubMed up to 30 April 2017. Random-effects meta-analyses were conducted to summarize the relative risks across studies.

RESULTS

One hundred and twenty-six observational cohort studies comprising over 22,900 premenopausal and 103,000 postmenopausal breast cancer cases were meta-analyzed. Higher physical activity was inversely associated with both pre- and postmenopausal breast cancers, whereas increased sitting time was positively associated with postmenopausal breast cancer. Although higher early adult BMI (ages 18-30 years) was inversely associated with pre- and postmenopausal breast cancers, adult weight gain and greater body adiposity increased breast cancer risk in postmenopausal women, and the increased risk was evident for HR+ but not HR- breast cancers, and among never but not current users of postmenopausal hormones. The evidence was less consistent in premenopausal women. There were no associations with adult weight gain, inverse associations with adult BMI (study baseline) and hip circumference, and non-significant associations with waist circumference and waist-to-hip ratio that were reverted to positive associations on average in studies accounting for BMI. No significant associations were observed for HR-defined premenopausal breast cancers.

CONCLUSION

Better understanding on the impact of these factors on pre- and postmenopausal breast cancers and their subtypes along the life course is needed.

Association of BMI and height with the risk of endometrial cancer, overall and by histological subtype: a population-based prospective cohort study in Japan

Evidence on the association between BMI, height, and endometrial cancer risk, including by subtypes, among Asian populations remains limited. We evaluated the impact of BMI and height on the risk of endometrial cancer, overall and by histological subtype. We prospectively investigated 53 651 Japanese women aged 40-69 years. With an average follow-up duration of 18.6 years, 180 newly diagnosed endometrial cancers were reported, including 119 type 1 and 21 type 2. The association between BMI, height, and endometrial cancer risk was assessed using a Cox proportional hazards regression model with adjustment for potential confounders. Overweight and obesity were associated positively with the risk of endometrial cancer. Compared with BMI of 23.0-24.9 kg/m, hazard ratios (HRs) (95% confidence intervals) were 1.93 (1.17-3.16) for BMI of 27.0-29.9 kg/m and 2.37 (1.20-4.66) for BMI of at least 30.0 kg/m. On analysis by histological subtype, with each increase in BMI of 5 U, the estimated HR of type 1 endometrial cancer increased (HR=1.54, 95% confidence interval: 1.21-1.98), but HR of type 2 endometrial cancer was unaffected. There was no statistically significant association between height and endometrial cancer risk. In conclusion, the risk of endometrial cancer was elevated in women with a BMI of at least 27.0 kg/m. By histological subtype, BMI was associated with type 1, but not type 2 endometrial cancer risk among a population with a relatively low BMI compared with western populations.

The Health Burden of Cancer Attributable to Obesity in Korea: A Population-Based Cohort Study

PURPOSE

Considering the health impact of obesity and cancer, it is important to estimate the burden of cancer attributable to high body mass index (BMI). Therefore, the present study attempts to measure the health burden of cancer attributable to excess BMI, according to cancer sites.

MATERIALS AND METHODS

The present study used nationwide medical check-up sample cohort data (2002-2015). The study subjects were 496,390 individuals (268,944 men and 227,446 women). We first calculated hazard ratio (HR) in order to evaluate the effect of excess BMI on cancer incidence and mortality. Then, the adjusted HR values and the prevalence of excess BMI were used to calculate the population attributable risk. This study also used the Global Burden of Disease method, to examine the health burden of obesity-related cancers attributable to obesity.

RESULTS

The highest disability-adjusted life year (DALY) values attributable to overweight and obesity in men were shown in liver cancer, colorectal cancer, and gallbladder cancer. Among women, colorectal, ovarian, and breast (postmenopausal) cancers had the highest DALYs values attributable to overweight and obesity. Approximately 8.0% and 12.5% of cancer health burden (as measured by DALY values) among obesity-related cancers in men and women, respectively, can be prevented.

CONCLUSIONS

Obesity has added to the health burden of cancer. By measuring the proportion of cancer burden attributable to excess BMI, the current findings provide support for the importance of properly allocating healthcare resources and for developing cancer prevention strategies to reduce the future burden of cancer.

The economic burden of cancer attributable to obesity in Korea: A population-based cohort study

OBJECTIVE

Cancer is a major cause of the burden of disease, and obesity is widely recognised one of the most important modifiable risk factor of cancer. Considering the economic impact of obesity and cancer, it is necessary to measure the economic burden of cancer attributable to excess body mass index (BMI).

METHODS

This study used medical check-up sample cohort data of National Health Insurance Service (NHIS) claims and during 2002-2015. To estimate the costs (direct and indirect) according to obesity-related cancer sites, we performed a Cox proportional hazard model and cost of illness (COI) methods.

RESULTS

Among male obesity-related cancer sites, the largest total costs caused by overweight or obesity were 5.5 trillion USD for liver cancer, 1.8 trillion USD for colorectal cancer and 1.6 trillion USD for kidney cancer. Among women, post-menopausal breast, liver and colorectal cancers had the largest total costs attributable to excess BMI (breast: 3.7 trillion USD, liver: 2.3 trillion USD, colorectal: 2.1 trillion USD).

CONCLUSIONS

Approximately, 4.5% and 15.8% of total costs in obesity-related cancers can be reduced in men and women respectively. This study's findings highlight the importance of improved interventions, which can yield healthier lives and economic benefits beyond simply reducing cancer incidence and mortality.

Body size and obesity during adulthood, and risk of lympho-haematopoietic cancers: an update of the WCRF-AICR systematic review of published prospective studies

BACKGROUND

To summarise the evidence on the associations between body mass index (BMI) and BMI in early adulthood, height, waist circumference (WC) and waist-to-hip ratio (WHR), and risk of lympho-haematopoietic cancers.

METHOD

We conducted a meta-analysis of prospective studies and identified relevant studies published up to December 2017 by searching PubMed. A random-effects model was used to calculate dose-response summary relative risks (RRs).

RESULTS

Our findings showed BMI, and BMI in early adulthood (aged 18-21 years) is associated with the risk of Hodgkin's and non-Hodgkin's lymphoma (HL and NHL), diffuse large beta-cell lymphoma (DLBCL), Leukaemia including acute and chronic myeloid lymphoma (AML and CML), and chronic lymphocytic leukaemia (CLL) and multiple myeloma (MM). The summary RR per 5 kg/m2 increase in BMI were 1.12 [95% confidence interval (CI): 1.05-1.20] for HL, 1.05 (95% CI: 1.03-1.08) for NHL, 1.11 (95% CI: 1.05-1.16) for DLBCL, 1.06 (95% CI: 1.03-1.09) for ML, 1.09 (95% CI: 1.03-1.15) for leukaemia, 1.13 (95% CI: 1.04-1.24) for AML, 1.13 (95% CI: 1.05-1.22) for CML and 1.04 (95% CI: 1.00-1.09) for CLL, and were1.12 (95% CI: 1.05-1.19) for NHL, 1.22 (95% CI: 1.09-1.37) for DLBCL, and 1.19 (95% CI: 1.03-1.38) for FL for BMI in early adulthood analysis. Results on mortality showed a 15%, 16% and 17% increased risk of NHL, MM and leukaemia, respectively. Greater height increased the risk of NHL by 7%, DLBCL by 10%, FL by 9%, MM by 5% and Leukaemia by 7%. WHR was associated with increased risk of DLBCL by 12%. No association was found between higher WC and risk of MM.

CONCLUSION

Our results revealed that general adiposity in adulthood and early adulthood, and greater height may increase the risk of almost all types of lympho-haematopoietic cancers and this adds to a growing body of evidence linking body fatness to several types of cancers.

Association between mammographic density and tumor marker-defined breast cancer subtypes: a case-control study

High mammographic density (MD) is the most important risk factor for breast cancer. This study aimed to clarify the relationship between MD and breast cancer subtypes defined by tumor markers. We enrolled 642 women with breast cancer (69% premenopausal) and 1241 controls matched for age and menopausal status. Absolute mammographic dense area (ADA), percent mammographic dense area (PDA), and nondense area were assessed using a computer-assisted thresholding technique. We classified breast cancer cases into four subtypes using information on tumor marker expression such as estrogen receptor (ER), progesterone receptor (PR), and Cerb2 receptor (HER2); luminal A (ER+ and/or PR+, HER2-), luminal B (ER+ and/or PR+, HER2+), HER2-overexpressing (ER-, PR-, and HER2+), and triple-negative (ER-, PR-, and HER2-). Analysis was carried out using a conditional logistic regression model with adjustment for covariates. ADA and PDA were associated positively with the risk of breast cancer overall. Both ADA and PDA tended to have a positive association with breast cancer with any ER, any PR, or HER2-, but not for HER2+. The risk of luminal A breast cancer increased significantly 1.11 times (95% confidence interval: 1.01-1.23) for ADA and 1.12 times (95% confidence interval: 1.01-1.24) for PDA, estimated per 1 SD of the age and BMI-adjusted MD. However, the risk of breast cancer with luminal B, HER2-overexpressing, and triple-negative subtypes did not differ (P>0.10). Differential associations between MD measures and breast cancer by tumor marker status or tumor marker-defined subtypes were not detected. These findings suggested that the association between MD and breast cancer subtype may be because of other causal pathways.

Anthropometric characteristics, physical activity and risk of hematological malignancies: A systematic review and meta-analysis of cohort studies

Overweight/obesity, adult attained height and physical activity are possible risk factors for hematological malignancies. This meta-analysis aims to evaluate the associations between these factors and hematological cancer risk in adults. Eligible cohort studies were sought in PubMed up to May 31, 2016; overall, 44 studies were included in the present analyses. Pooled relative risk estimates were calculated using random-effects models; separate analyses were conducted for non-Hodgkin lymphoma (NHL) and subtypes (diffuse large B-cell lymphoma, DLBCL; follicular cell lymphoma; small lymphocytic lymphoma/chronic lymphocytic leukemia, SLL/CLL), Hodgkin lymphoma (HL), multiple myeloma (MM), leukemia and subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, AML). Obesity was associated with increased risk of NHL, HL, MM, leukemia overall and AML in both sexes, as well as with higher DLBCL risk in women; the dose-response meta-regression analysis confirmed these associations. Less pronounced effects were observed regarding overweight, as it was associated with increased MM risk in both sexes, NHL risk in males, DLBCL and overall leukemia risk in females. Taller men presented with significantly higher risk of NHL and taller women were affected by higher risk of NHL, DLBCL, FL, CLL/SLL, MM, leukemia and AML. On the other hand, physical activity and abdominal fatness were not associated with the risk of hematological malignancies. In conclusion, this meta-analysis highlights the pivotal role of anthropometric measures in shaping the risk of hematological malignancies in adults. Additional, well-designed studies stemming from all the continents are needed for the further substantiation and generalization of the results.

Effects of exercise type on estrogen, tumor markers, immune function, antioxidant function, and physical fitness in postmenopausal obese women

This study aims to identify the effects of exercise type on estrogen, tumor markers, immune function, antioxidant function, and physical fitness in postmenopausal obese women. The subjects were 30 post-menopausal obese women with body fat percentage higher than 30%. Participants were divided into aerobic exercise group (n=10; age, 53.70±3.37 years), resistance exercise group (n=10; age, 52.20±2.15 years), and control group (n=10; age, 52.50±2.68 years). Estrogen and growth hormone showed no significant difference in the aerobic exercise group, resistance exercise group, and control group. Tumor marker alpha-fetoprotein was increased in the aerobic exercise, resistance exercise, and control groups (P<0.01). The metabolic syndrome risk factor was decreased in the aerobic and resistance exercise groups, which was shown by the reduction of weight (P<0.001), body fat percentage (P<0.001), waist circumference (P<0.05), and increase of high density lipoprotein-cholesterol (P<0.001). natural killer cell activity was increased in the aerobic exercise group, resistance exercise group, and control group (P<0.001). Oxidative stress was decreased in the aerobic exercise group, resistance exercise group, and control group (P<0.001). Maximum oxygen uptake was increased in the aerobic and resistance exercise groups, but aerobic exercise was more effective (P<0.05). Knee isokinetic extensor muscle was increased in both the aerobic and resistance exercise groups (P<0.001). Aerobic and resistance exercise of postmenopausal obese women can be considered an effective intervention program to prevent metabolic syndrome and improve physical fitness.

The association between BMI and kidney cancer risk: An updated dose-response meta-analysis in accordance with PRISMA guideline

OBJECTIVE

Obesity is considered as one of the risk factors of kidney cancer. However, the results are not consistent in reported original studies, as well as in published meta-analysis. This study aims to clarify the relationship between overweight/obesity and kidney cancer by an updated overall and dose-response meta-analysis.

METHODS

This meta-analysis was conducted in accordance with PRISMA guideline. Relevant studies were searched using PubMed, Embase, and Web of Science databases. The studies were limited to human cohort studies in English and Chinese language. Random-effect models and dose-response meta-analysis were used to synthesize the results. Subgroup analyses were also conducted based on the characteristics of participants.

RESULTS

Twenty-four cohort studies with 8,953,478 participants were included in our meta-analysis. Compared to the normal weight, the pooled RRs of kidney cancer was 1.35 (1.27-1.43) in overweight and 1.76 (1.61-1.91) in obese participants. An increased kidney cancer risk of 1.06 (1.05-1.06) for each 1 kg/m increase in BMI was showed in dose-response meta-analysis. No significant heterogeneity was found across studies with I = 39.4% for overweight, and I = 43.3% for obesity.

CONCLUSION

The overall and dose-response meta-analysis suggested that overweight/obesity increases the risk of kidney cancer both in men and women.

Waist circumference and risk of 23 site-specific cancers: a population-based cohort study of Korean adults

BACKGROUND

Large waist circumference (WC) is a risk factor for several site-specific cancers, but a large-scale systematic investigation across all common cancers adjusted for potential confounders has not been conducted. This study aimed to evaluate the possible links between WC and common cancers.

METHODS

We prospectively examined the association between WC and the risk of cancers in a 7-year cohort study of nearly 22.9 million Korean adults. Using the claims database merged with the national health check-up data, we fitted proportional hazard models to investigate associations between WC and 23 of the most common cancers, with adjustment for potential confounders, including body mass index (BMI). We also evaluated the modification of BMI on the relationships between WC and the incidence of cancer.

RESULTS

A total of 769,871 cancer cases were identified. WC was positively associated with 18 of 23 cancers, and the effects varied substantially by site in each sex. The modification of BMI on the WC-cancer association also varied across the cancer site; in most cases it mitigated the association. For cancers of the oral cavity, larynx, oesophagus, lung, and premenopausal breast, the BMI adjustment reversed the association toward being positive (all P_trend < 0.001).

CONCLUSIONS

Central obesity, independent of general obesity, was associated with the risk of several cancers. The heterogeneity in the mediating effects of BMI suggests that different mechanisms are associated with different cancer sites. Based upon these findings, active strategies to monitor and prevent central obesity should be implemented.

The association between thyroid cancer and insulin resistance, metabolic syndrome and its components: A systematic review and meta-analysis

BACKGROUND

Thyroid cancer is rapidly increasing in incidence worldwide in the past several decades, same as the incidence of metabolic syndrome. We performed a system review and meta-analysis of the association between metabolic syndrome, its components and insulin resistance and thyroid cancer incidence.

METHODS

We searched several computer-assisted databases PUBMED, EMBASE and ISI Web of Science to identify studies published before 31st January 2018. Every study must report either risk estimates of thyroid cancer incidence with 95% confidence interval (CI) or related data can speculate. Two investigators independently identified eligible studies and extracted data. Evaluating the summaries of relative risk estimates use both fixed and random effects methods.

RESULTS

We found 42 articles met the inclusion criteria of this review. There is an increased risk for thyroid cancer for patients with insulin resistance (relative risk [RR] = 1.59, 95%confidence interval [CI] = 1.12-2.27, P = 0.01), dysglycemia (RR = 1.40, 95%CI = 1.15-1.70,P < 0.001), high BMI (RR = 1.35,95%CI = 1.23-1.48,P < 0.001) and hypertension(RR = 1.34,95%CI = 1.22-1.47, p < 0.001). However, patients with dyslipidemia, both total cholesterol (RR = 1.09, 95%CI = 0.98-1.21, P = 0.13) and triglyceride (RR = 1.01, 95%CI = 0.91-1.12, P = 0.82) was not associated with thyroid cancer.

CONCLUSIONS

Our meta-analysis showed Insulin Resistance, dysglycemia, high BMI and hypertension significantly increased the thyroid cancer risk. These results may help identify people with high risk of thyroid cancer and change to healthy life style.

Height and body fatness and colorectal cancer risk: an update of the WCRF-AICR systematic review of published prospective studies

PURPOSE

There is no published dose-response meta-analysis on the association between height and colorectal cancer risk (CRC) by sex and anatomical sub-site. We conducted a meta-analysis of prospective studies on the association between height and CRC risk with subgroup analysis and updated evidence on the association between body fatness and CRC risk.

METHODS

PubMed and several other databases were searched up to November 2016. A random effects model was used to calculate dose-response summary relative risks (RR's).

RESULTS

47 studies were included in the meta-analyses including 50,936 cases among 7,393,510 participants. The findings support the existing evidence regarding a positive association of height, general and abdominal body fatness and CRC risk. The summary RR were 1.04 [95% (CI)1.02-1.05, I² = 91%] per 5 cm increase in height, 1.02 [95% (CI)1.01-1.02, I² = 0%] per 5 kg increase in weight, 1.06 [95% (CI)1.04-1.07, I² = 83%] per 5 kg/m2 increase in BMI, 1.02 [95% (CI)1.02-1.03, I² = 4%] per 10 cm increase in waist circumference, 1.03 [95% (CI)1.01-1.05, I² = 16%] per 0.1 unit increase in waist to hip ratio. The significant association for height and CRC risk was similar in men and women. The significant association for BMI and CRC risk was stronger in men than in women.

CONCLUSION

The positive association between height and risk of CRC suggests that life factors during childhood and early adulthood might play a role in CRC aetiology. Higher general and abdominal body fatness during adulthood are risk factors of CRC and these associations are stronger in men than in women.

Body mass index and lung cancer risk in never smokers: a meta-analysis

Background

Obesity is found to increase the risk of most cancer types, but reduce lung cancer risk in many studies. However, the association between obesity and lung cancer is still controversial, mainly owing to the confounding effect of smoking.

Methods

Eligible studies were identified from electric databases to July 1, 2017. Relevant data were extracted and pooled using random-effects models; dose-response and subgroup analyses were also performed.

Results

Twenty-nine studies with more than 10,000 lung cancer cases in15 million never smokers were included. Compared with normal weight, the summary relative risk (RR) was 0.77(95% confidence interval [CI]: 0.68–0.88, P < 0.01) for excess body weight (body mass index [BMI] ≥ 25 kg/m²). An inverse linear dose-response relationship was observed between BMI and lung cancer risk in never smokers, with an RR of 0.89(95% CI: 0.84–0.95, P < 0.01) per 5 kg/m² increment in BMI. The results remained stable in most subgroup analyses. However, when stratified by sex, a significant inverse association existed in women but not in men. Similar results were found in analyses for other categories of BMI.

Conclusion

Our results indicate that higher BMI is associated with lower lung cancer risk in never smokers.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4543-y) contains supplementary material, which is available to authorized users.

The risk of thyroid cancer and obesity: A nationwide population-based study using the Korea National Health Insurance Corporation cohort database

INTRODUCTION

In recent years, the incidence of thyroid cancer and obesity has increased rapidly worldwide. Many studies have been conducted on the relationship between thyroid cancer and obesity; however, the potential mechanisms are not well understood, and few studies have been performed in Asia. This study aimed to identify the relationship between the risk of thyroid cancer and obesity in the Korean population based on a large cohort of data.

METHOD

We analyzed clinical data from a total of 351,402 individuals (males: 181,709, females: 169,693) aged over 20 years who received medical examinations arranged by the national insurance program from 2003 to 2008. Newly diagnosed thyroid cancer was identified using insurance claims data. The median follow-up duration was 7.01 years.

RESULTS

The mean body mass index (BMI) of the subjects was 23.6 ± 3.2 kg/m² (males, 24 ± 3; females, 23.1 ± 3.3). A total of 3308 individuals (0.94%) developed thyroid cancer during the study period. The risk of thyroid cancer was higher with increasing BMI in both men and women. Hazard ratios (95% confidence interval) for obese (25-29.9 kg/m²) and extremely obese (≥30 kg/m²) groups were 1.23 (1.13-1.34) and 1.26 (1.02-1.50), respectively, compared to the normal group (18.5-22.9 kg/m2). In particular, the association between the risk of thyroid cancer and BMI was more remarkable in the male group than female group.

CONCLUSION

Our findings show that higher BMI is positively associated with the risk of thyroid cancer. Furthermore, this study supports the positive association between obesity and the increased incidence of thyroid cancer.

Epidemiologic Evidence That Excess Body Weight Increases Risk of Cervical Cancer by Decreased Detection of Precancer

Purpose Obesity has been inconsistently linked to increased cervical cancer incidence and mortality; however, the effect of obesity on cervical screening has not been explored. We investigated the hypothesis that increased body mass might decrease detection of cervical precancer and increase risk of cervical cancer even in women undergoing state-of-the-art screening. Methods We conducted a retrospective cohort study of 944,227 women age 30 to 64 years who underwent cytology and human papillomavirus DNA testing (ie, cotesting) at Kaiser Permanente Northern California (January 2003 to December 2015). Body mass index was categorized as normal/underweight (< 25 kg/m²), overweight (25 to < 30 kg/m²), or obese (≥ 30 kg/m²). We estimated 5-year cumulative risks of cervical precancer and cancer by category of body mass index using logistic Weibull survival models. Results We observed lower risk of cervical precancer (n = 4,489) and higher risk of cervical cancer (n = 490) with increasing body mass index. Specifically, obese women had the lowest 5-year risk of precancer (0.51%; 95% CI, 0.48% to 0.54% v 0.73%; 95% CI, 0.70% to 0.76% in normal/underweight women; P trend < .001). In contrast, obese women had the highest 5-year risk of cancer (0.083%; 95% CI, 0.072% to 0.096% v 0.056%; 95% CI, 0.048% to 0.066% in normal/underweight women; P trend < .001). Results were consistent in subgroups defined by age (30 to 49 v 50 to 64 years), human papillomavirus status (positive v negative), and histologic subtype (glandular v squamous). Approximately 20% of cervical cancers could be attributed to overweight or obesity in the women in our study who underwent routine cervical screening. Conclusion In this large, screened population, overweight and obese women had an increased risk of cervical cancer, likely because of underdiagnosis of cervical precancer. Improvements in equipment and/or technique to assure adequate sampling and visualization of women with elevated body mass might reduce cervical cancer incidence.

The association between BMI and gallbladder cancer risk: a meta-analysis

Obesity is a known cause of gallstone formation and gallstones increases the risk of gallbladder cancer (GBC), but the relation of body mass index (BMI) to GBC remains incompletely understood. To help elucidate the role of obesity in GBC, we performed a meta-analysis of the relationship between BMI and GBC risk. PUBMED and EMBASE databases were searched up to April 17, 2016. Fifteen articles with 5902 cases were identified. Random-effects models and dose-response meta-analyses were used to pool study results. Compared to normal weight, the pooled relative risks (RRs) and the corresponding 95% confidence intervals (CI) of GBC for overweight and obesity is 1.10 (0.98-1.23) and 1.58 (1.43-1.75) respectively. The RRs and 95% CI of overweight and obesity in man are 0.98 (0.90-1.08) and 1.43 (1.19-1.71), while the corresponding RRs in woman are 1.29 (1.08-1.55) and 1.68 (1.41-2.00) when compared to normal weight. A nonlinear dose-response relationship between BMI and risk of GBC was found (P=0.001), and the risk increased by 4% for each 1 kg/m2 increment in BMI. When adjusted for sex, at the point of BMI=25 kg/m2, the RRs (95% CIs) for women and men were 1.13 (1.01-1.25) and 0.98 (0.90-1.07) respectively. The corresponding RRs (95%CIs) at the point of BMI=30 kg/m2 were 1.56(1.39-1.75) vs. 1.24(1.06-1.44). These results suggest that association of obesity and risk of GBC is stronger in woman. Furthermore, overweight is only associated with GBC in woman. A even stricter weight control might be necessary for woman to prevent GBC.

Body mass index had different effects on premenopausal and postmenopausal breast cancer risks: a dose-response meta-analysis with 3,318,796 subjects from 31 cohort studies

Background

There is sufficient evidence supporting a relationship between increased body mass index (BMI) and an increased risk for breast cancer among postmenopausal women. However, most studies have found a decreased risk for premenopausal breast cancer. This study was conducted to find out the different effects of BMI on the risk of breast cancer among premenopausal and postmenopausal women, and explore the potential factors that influence the associations.

Methods

A dose-response meta-analysis with 3,318,796 participants from 31 articles was conducted. Cohort studies that included BMI and corresponding breast cancer risk were selected through various databases including PubMed, Medline, Web of Science, the China National Knowledge Infrastructure (CNKI) and Chinese Scientific Journals (VIP). Random effects models were used for analyzing the data.

Results

The summary relative risks (RRs) were 1.33 (95%CI: 1.20–1.48) and 0.94(95%CI: 0.80–1.11) among postmenopausal and premenopausal women, respectively. The dose-response meta-analysis indicated a positive non-linear association between BMI and breast cancer risk among postmenopausal women, and compared to the mean level of the normal BMI category (21.5 kg/m²) the RR in total postmenopausal women were1.03 (95% CI: 1.02–1.05) per 1 kg/m² increment. However, no statistically significant association among total premenopausal women was detected. In subgroup analysis among European premenopausal women, the summary RR was 0.79(95%CI: 0.70–0.88). The non-linear relationship showed a negative non-linear association between BMI and breast cancer risk among European premenopausal women. When compared to the mean level of the normal BMI category, the RRs were 0.98 (95%CI: 0.96–1.00) per 1 kg/m² increment, respectively.

Conclusions

In line with previous studies BMI had different effects on pre-menopausal and postmenopausal breast cancer risk. However, contrary to previous studies, a high BMI was not associated with decreased risk in total pre-menopausal women. More research is needed to better understand these differences.

Electronic supplementary material

The online version of this article (10.1186/s12889-017-4953-9) contains supplementary material, which is available to authorized users.

Body Mass Index Can Increase the Risk of Gallbladder Cancer: A Meta-Analysis of 14 Cohort Studies

BACKGROUND This study sought to appraise the association between raised body mass index (BMI) and the risk of gallbladder cancer (GBC) by performing a meta-analysis of 14 cohort studies. MATERIAL AND METHODS Eligible cohort studies were selected by searching PubMed and EMBASE from their inception to May 26, 2016, and the reference lists of retrieved articles were also consulted. The information was screened by two authors separately. We used a fixed-effects model to calculate the overall pooled risk estimates. A random-effects model was used to identify heterogeneity. RESULTS The meta-analysis incorporated 14 cohort studies. Nine papers were deemed to be of high quality based on the Newcastle-Ottawa Scale (NOS). Compared with normal weight (BMI 18.5-24.9 kg/m²), the overall pooled relative risks (RR) of GBC was 1.45 (95% CI 1.30-1.61) for excess body weight individuals (BMI ≥25 kg/m²); 1.10 (95% CI 1.02-1.18) for overweight persons (BMI 25-29.9 kg/m²) and 1.69(95% CI 1.54-1.86) for obese folks (BMI ≥30 kg/m²). A higher risk of GBC was presented in obese women (women: RR 1.78, 95% CI 1.59-1.99; men: RR 1.50, 95% CI 1.25-1.79). And a positive relationship between overweight and GBC risk was also displayed in female (RR 1.25, 95% CI 1.11-1.40), but not in male (RR 1.01, 95% CI 0.93-1.11). The sensitivity analysis indicated stable results, and no publication bias was observed. CONCLUSIONS This meta-analysis of 14 cohort studies demonstrated that raised BMI has a dramatic association with risk of GBC, especially in women. But, no association between overweight and GBC in men was found.

Body mass index and incidence of thyroid cancer in Korea: the Korean Cancer Prevention Study-II

PURPOSE

The prevalence of thyroid cancer and obesity has increased worldwide. However, their association has remained controversial and few studies have been performed in Asia. Our study evaluated the correlation between the incidence of thyroid cancer and body mass index (BMI) in Korea.

METHODS

This is a multi-centered, prospective cohort study from the Korean Cancer Prevention Study-II. A total of 141,157 individuals between 1994 and 2012, including 1546 newly developed thyroid cancer patients, were enrolled. Subjects were divided into four groups on the BMI. Person-years, incidence rate, and hazard ratios (HRs) were calculated using the Cox proportional hazard model.

RESULTS

The increasing trends of HRs of thyroid cancer in men and women younger than 50 years of age were observed as BMI increased (P trend <0.001 in both groups). However, in women older than 50 years of age, there was no association between thyroid cancer incidence and BMI.

CONCLUSIONS

Our findings suggest that positive association between thyroid cancer incidence and high BMI in men and women under 50 years old. Based on these results, we suggest that obese men and women under 50 years old are better to be considered for the higher possibility of thyroid cancer development, and more efforts are needed to control weight gain.

Overweight, obesity and the risk of gallbladder and extrahepatic bile duct cancers: A meta-analysis of observational studies

OBJECTIVE

Epidemiological studies have repeatedly investigated the association between excess body weight and the risk of biliary tract cancer with inconsistent results. The objective of this study was to quantitatively assess the associations between overweight and obesity and the risk of biliary tract cancer.

METHODS

A comprehensive search of PubMed, Embase, Web of Science, and China National Knowledge Infrastructure databases up to August 2015 was conducted, and the reference lists of retrieved articles for additional relevant studies were manually searched.

RESULTS

Fourteen prospective cohort studies and 15 case-control studies were included in this meta-analysis. These studies included 11,448,397 participants (6,733 patients with gallbladder cancer [GBC] and 5,798 patients with extrahepatic bile duct cancer [EBDC]) with follow-up durations ranging from 5 to 23 years. Among overweight adults, the pooled RR was 1.17 (95% CI, 1.07-1.28) for GBC and 1.26 (95% CI, 1.14-1.39) for EBDC, and among people with obesity, the pooled RR was 1.62 (95% CI, 1.49-1.75) for GBC and 1.48 (95% CI, 1.21-1.81) for EBDC. Visual inspection of the funnel plots and the Begg's and the Egger's tests did not show enough evidence of publication bias.

CONCLUSIONS

Integrated evidence from this meta-analysis suggests that excess body weight is associated with a significantly increased risk of GBC and EBDC.

Obesity over the life course and risk of acute myeloid leukemia and myelodysplastic syndromes

BACKGROUND

Overweight and obesity are known risk factors for a number of cancers, with recent evidence suggesting that risk of hematologic cancer is also increased in obese individuals. We evaluated associations between body mass index (BMI) at differing time points during the life course in population-based case control studies of acute myeloid leukemia (AML) and myelodysplatic syndromes (MDS).

METHODS

Cases were identified by the Minnesota Cancer Surveillance System. Controls were identified through the Minnesota State driver's license/identification card list. BMI was calculated using self-reported height and weight at ages 18, 35, and 50 years and two years prior to interview, and categorized as normal (18.5-25 kg/m(2)), overweight (25-29.9 kg/m(2)), obese class I (30-34.9 kg/m(2)), and obese class II/III (35+ kg/m(2)). All analyses were stratified by sex. Unconditional logistic regression was used to calculate odds ratios and 95% confidence intervals.

RESULTS

We included 420 AML cases, 265 MDS cases and 1388 controls. Obesity two years prior to diagnosis was associated with AML in both males and females (OR=2.22, 95% CI 1.28, 3.85 and OR=1.85, 95% CI 1.08, 3.15 for BMI≥35 vs. BMI 18.5-24.9, respectively). In contrast, associations between obesity and MDS were observed only in females. Weight change in adulthood was not consistently associated with either outcome.

CONCLUSION

Our results extend the emerging literature suggesting that obesity is a risk factor for hematologic malignancy and provide evidence that that the association remains regardless of timing of obesity. Obesity in adulthood is a modifiable risk factor for both MDS and AML.

Obesity and Endometrial Cancer

Endometrial cancer is the sixth most common cancer in women worldwide and the most common gynecologic malignancy in the developed world. This chapter explores the current epidemiologic evidence on the association between obesity and endometrial cancer risk and mortality. Using body mass index (BMI) as a measure of obesity, we found that obesity (defined as BMI > 30 and < 35 kg/m²) was associated with a 2.6-fold increase in endometrial cancer risk, while severe obesity (BMI > 35 kg/m²) was associated with a 4.7-fold increase compared to normal-weight women (BMI < 25 kg/m²). Increased central adiposity also increased endometrial cancer risk by 1.5- to twofold. Among both healthy and endometrial cancer patient populations, obesity was associated with a roughly twofold increase in endometrial cancer-specific mortality. This risk reduction was also observed for obesity and all-cause mortality among endometrial cancer patients. In the few studies that assessed risk associated with weight change, an increased endometrial cancer risk with weight gain and weight cycling was observed, whereas some evidence for a protective effect of weight loss was found. Furthermore, early-life obesity was associated with a moderately increased risk of endometrial cancer later in life. There are several mechanisms whereby obesity is hypothesized to increase endometrial cancer risk, including increased endogenous sex steroid hormones, insulin resistance, chronic inflammation and adipokines. Further research should focus on histological subtypes or molecular phenotypes of endometrial tumors and population subgroups that could be at an increased risk of obesity-associated endometrial cancer. Additionally, studies on weight gain, loss or cycling and weight loss interventions can provide mechanistic insight into the obesity-endometrial cancer association. Sufficient evidence exists to recommend avoiding obesity to reduce endometrial cancer risk.

Impact of post-laparoscopic sleeve gastrectomy weight loss on C-reactive protein, lipid profile and CA-125 in morbidly obese women

Introduction

Obesity increases production of adipose tissue-derived proteins, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Also there are elevated levels of C-reactive protein (CRP) and IL-6, CD8, and CD4, indicating chronic subclinical inflammation. Since obesity represents a serious risk factor in several metabolic diseases, identifying the status of carbohydrate antigen-125 (CA-125) would further link obesity and tumors.

Aim

To examine the effect of weight loss by laparoscopic sleeve gastrectomy (LSG) on plasma CRP, lipid profiles and CA-125 level in morbidly obese patients.

Material and methods

This prospective study was conducted in the Surgery Department, Fayoum University Hospital, between August 2013 and September 2015. To assess the effect of excess weight loss following this operation CRP, lipid profile and CA-125 were measured before and 12 months after the LSG operation for weight loss. The study included 30 cases of morbidly obese patients: 30 (100%) females aged 23–55 years who were considered clinically obese with a mean body mass index of 42.71 ±4.3 (38–46) kg/m² and mean age of 40.3 ±8.5 (23–55) years. The National Institute of Health (NIH) inclusion criteria for bariatric surgery were used.

Results

A mean weight loss of 29.30% decreased plasma CRP, triglycerides, total cholesterol and low-density lipoprotein cholesterol (HDL cholesterol), CA-125 level and increased high-density lipoprotein cholesterol (HDL cholesterol) The percentage weight loss was significantly associated with changes in plasma CRP, triglycerides, total cholesterol, total HDL cholesterol and CA-125.

Conclusions

Weight loss by LSG improves inflammation, dyslipidemia and CA-125 level.

Adiposity and risk of thyroid cancer: a systematic review and meta-analysis

Thyroid cancer incidence has increased rapidly over time, as has obesity prevalence. A link between the two appears plausible, but the relation of adiposity to thyroid cancer remains incompletely understood. We performed a meta-analysis of adiposity measures and thyroid cancer using studies identified through October 2014. Twenty-one articles yielded data on 12,199 thyroid cancer cases. We found a statistically significant 25% greater risk of thyroid cancer in overweight individuals and a 55% greater thyroid cancer risk in obese individuals as compared with their normal-weight peers. Each 5-unit increase in body mass index (BMI), 5 kg increase in weight, 5 cm increase in waist or hip circumference and 0.1-unit increase in waist-to-hip ratio were associated with 30%, 5%, 5% and 14% greater risks of thyroid cancer, respectively. When evaluated by histologic type, obesity was significantly positively related to papillary, follicular and anaplastic thyroid cancers, whereas it revealed an inverse association with medullary thyroid cancer. Both general and abdominal adiposity are positively associated with thyroid cancer. However, relations with BMI vary importantly by tumour histologic type.

Body Mass Index and Risk of Gallbladder Cancer: Systematic Review and Meta-Analysis of Observational Studies

OBJECTIVES

To provide a quantitative assessment of the association between excess body weight, interpreted as increased body mass index (BMI), and the risk of gallbladder cancer (GBC).

METHODS

We identified eligible studies in Medline and EMBASE up to 1 February 2015, and reference lists of retrieved articles. Summary relative risks with their 95% confidence intervals were calculated in a random-effects model. Subgroup analyses were performed according to study design, gender, geographic location, ascertainment of exposure and adjustment for confounders.

RESUITS

A total of 12 cohort studies and 8 case-control studies were included in the meta-analysis. Overall, compared with "normal" weight, the summary relative risks of GBC were 1.14 (95% CI, 1.04-1.25) for overweight individuals (BMI 25-30 kg/m²) and 1.56 (95% CI, 1.41-1.73) for obese individuals (BMI > 30 kg/m²). Obese women had a higher risk of GBC than men did (women: SRRs 1.67, 95% CI 1.38-2.02; men: SRRs 1.42, 95% CI 1.21-1.66), and there was significant association between overweight and GBC risk in women (SRRs 1.26, 95% CI 1.13-1.40), but not in men (SRRs 1.06, 95% CI 0.94-1.20).

CONCLUSIONS

Findings from this meta-analysis indicate that obesity is associated with an increased risk of GBC, especially in women. Overweight is associated with GBC risk only in women.

Non-Hodgkin Lymphoma, Body Mass Index, and Cytokine Polymorphisms: A Pooled Analysis from the InterLymph Consortium

BACKGROUND

Excess adiposity has been associated with lymphomagenesis, possibly mediated by increased cytokine production causing a chronic inflammatory state. The relationship between obesity, cytokine polymorphisms, and selected mature B-cell neoplasms is reported.

METHOD

Data on 4,979 cases and 4,752 controls from nine American/European studies from the InterLymph consortium (1988-2008) were pooled. For diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), joint associations of body mass index (from self-reported height and weight) and 12 polymorphisms in cytokines IL1A (rs1800587), IL1B (rs16944, rs1143627), IL1RN (rs454078), IL2 (rs2069762), IL6 (rs1800795, rs1800797), IL10 (rs1800890, rs1800896), TNF (rs1800629), LTA (rs909253), and CARD15 (rs2066847) were investigated using unconditional logistic regression. BMI-polymorphism interaction effects were estimated using the relative excess risk due to interaction (RERI).

RESULTS

Obesity (BMI ≥ 30 kg/m(2)) was associated with DLBCL risk [OR = 1.33; 95% confidence interval (CI), 1.02-1.73], as was TNF-308GA+AA (OR = 1.24; 95% CI, 1.07-1.44). Together, being obese and TNF-308GA+AA increased DLBCL risk almost 2-fold relative to those of normal weight and TNF-308GG (OR = 1.93; 95% CI, 1.27-2.94), with a RERI of 0.41 (95% CI, -0.05-0.84; Pinteraction = 0.13). For FL and CLL/SLL, no associations with obesity or TNF-308GA+AA, either singly or jointly, were observed. No evidence of interactions between obesity and the other polymorphisms were detected.

CONCLUSIONS

Our results suggest that cytokine polymorphisms do not generally interact with BMI to increase lymphoma risk but obesity and TNF-308GA+AA may interact to increase DLBCL risk.

IMPACT

Studies using better measures of adiposity are needed to further investigate the interactions between obesity and TNF-308G>A in the pathogenesis of lymphoma.

Sociodemographic Differences in the Association Between Obesity and Stress: A Propensity Score-Matched Analysis from the Korean National Health and Nutrition Examination Survey (KNHANES)

Few population-based studies have used an econometric approach to understand the association between two cancer risk factors, obesity and stress. This study investigated sociodemographic differences in the association between obesity and stress among Korean adults (6,546 men and 8,473 women). Data were drawn from the Korean National Health and Nutrition Examination Survey for 2008, 2009, and 2010. Ordered logistic regression models and propensity score matching methods were used to examine the associations between obesity and stress, stratified by gender and age groups. In women, the stress level of the obese group was found to be 27.6% higher than the nonobese group in the ordered logistic regression; the obesity effect on stress was statistically significant in the propensity score-matched analysis. Corresponding evidence for the effect of obesity on stress was lacking among men. Participants who were young, well-educated, and working were more likely to report stress. In Korea, obesity causes stress in women but not in men. Young women are susceptible to a disproportionate level of stress. More cancer prevention programs targeting young and obese women are encouraged in developed Asian countries.

Anthropometric factors and endometrial cancer risk: a systematic review and dose-response meta-analysis of prospective studies

BACKGROUND

Greater body mass index (BMI) has been convincingly related to increased endometrial cancer risk, however, whether adiposity earlier in life or abdominal fatness is an independent risk factor and whether weight gain or greater height increases the risk is not clear.

METHODS

As part of the Continuous Update Project of the World Cancer Research Fund International, we conducted a systematic review and meta-analysis of prospective studies of the association between anthropometric measures and endometrial cancer risk and searched PubMed and several other databases up to February 2015. Summary relative risks (RRs) were calculated using a random-effects model.

RESULTS

Thirty prospective studies of BMI and endometrial cancer risk with 22 320 cases among 6 445 402 participants were included. The summary RR for a 5-unit increment was 1.54 [95% confidence interval (CI) 1.47-1.61, I(2) = 81%]. Although the test for non-linearity was significant, Pnon-linearity < 0.0001, and the curve was steeper within the overweight and obese BMI ranges, there was evidence of increased risk even within the high normal BMI range. The summary RR was 1.45 (95% CI 1.28-1.64, I(2) = 76%) per 5 BMI units for BMI in young adulthood, 1.18 (95% CI 1.14-1.23, I(2) = 67%) per 5 kg increase of weight, and 1.16 (95% CI 1.12-1.20, I(2) = 51%) per 5 kg of weight gained between young adulthood and study baseline, 1.27 (95% CI 1.17-1.39, I(2) = 71%) per 10 cm increase in waist circumference, 1.21 (95% CI 1.13-1.29, I(2) = 0%) per 0.1-unit increment in waist-to-hip ratio and 1.30 (95% CI 1.19-1.41, I(2) = 0%) per 10-cm increase in hips circumference. The summary RR was 1.15 (95% CI 1.09-1.22, I(2) = 61%) for a 10-cm increase in height.

CONCLUSIONS

All measures of adiposity were associated with increased risk of endometrial cancer, and in addition increasing height was associated with increased risk.

A comparitive study to evaluate the role of serum lipid levels in aetiology of carcinoma breast

INTRODUCTION

Breast cancer is the most common occurring cancer in women worldwide. Various factors that have lead to change in lifestyle are thought to be associated with increase in breast cancer incidence in Asian countries. Several clinical studies suggest the prognostic significance of serum lipid levels in breast cancer. Present study was planned to confirm the association of lipids levels with breast cancer.

MATERIALS AND METHODS

Lipid analyses was carried out on serum samples from 100 breast cancer patients and 100 control women, with a age group of 25 y and above. The case & control group included 50 premenopausal women and 50 postmenopausal women.

RESULTS

Patients of study group had high Low density lipoproteins (LDL) (p-value - 0.00), Triglycerides (TG) (p-value -0.001) and Total cholesterol (TC) (p-value -0.00) as compared to control group. There was no association of VLDL (p-value -0.436) and HDL (p-value -0.797) among study group and control group. There was no association of lipid levels in different grades of carcinoma.

CONCLUSION

High levels of LDL, TG and TC were associated with breast cancer. However, no association was there in different grades of carcinoma. So it may be concluded that, LDL, TG and TC may be having some role in aetiology of breast cancer. Therefore, early detection and control of these factors may help in reducing the incidence of breast cancer and ultimately social and economic burden on society.

Obesity and risk of thyroid cancer: evidence from a meta-analysis of 21 observational studies

BACKGROUND

Several studies have evaluated the association between obesity and thyroid cancer risk. However, the results remain uncertain. In this study, we conducted a meta-analysis to assess the association between obesity and thyroid cancer risk.

MATERIAL/METHODS

Published literature from PubMed, EMBASE, Springer Link, Ovid, Chinese Wanfang Data Knowledge Service Platform, Chinese National Knowledge Infrastructure (CNKI), and Chinese Biology Medicine (CBM) were retrieved before 10 August 2014. We included all studies that reported adjusted risk ratios (RRs), hazard ratios (HRs) or odds ratios (ORs), and 95% confidence intervals (CIs) of thyroid cancer risk.

RESULTS

Thirty-two studies (n=12 620 676) were included in this meta-analysis. Obesity was associated with a significantly increased risk of thyroid cancer (adjusted RR=1.33; 95% CI, 1.24-1.42; I2=25%). In the subgroup analysis by study type, increased risk of thyroid cancer was found in cohort studies and case-control studies. In subgroup analysis by sex, both obese men and women were at significantly greater risk of thyroid cancer than non-obese subjects. When stratified by ethnicity, significantly elevated risk was observed in Caucasians and in Asians. In the age subgroup analysis, both young and old populations showed increased thyroid cancer risk. Subgroup analysis on smoking status showed that increased thyroid cancer risks were found in smokers and in non-smokers. In the histology subgroup analyses, increased risks of papillary thyroid cancer, follicular thyroid cancer, and anaplastic thyroid cancer were observed. However, obesity was associated with decreased risk of medullary thyroid cancer.

CONCLUSIONS

Our results indicate that obesity is associated with an increased thyroid cancer risk, except medullary thyroid cancer.

Body mass index and risk of breast cancer: a nonlinear dose-response meta-analysis of prospective studies

The role of Body Mass Index (BMI) for Breast Cancer (BC) remains to be great interest for a long time. However, the precise effect of nonlinear dose-response for BMI and BC risk is still unclear. We conducted a dose-response meta-analysis to quantitatively assess the effect of BMI on BC risk. Twelve prospective studies with 4,699 cases identified among 426,199 participants and 25 studies of 22,809 cases identified among 1,155,110 participants in premenopausal and postmenopausal groups, respectively, were included in this meta-analysis. Significant non-linear dose-response (P < 0.001) association was identified between BMI and BC risk in postmenopausal women. Individuals with BMI of 25, 30, and 35 kg/m² yielded relative risks (RRs) of 1.02 [95% confidence interval (CI): 0.98–1.06], 1.12 (95% CI: 1.01–1.24), and 1.26 (95% CI: 1.07–1.50), respectively, when compared to the mean level of the normal BMI range. However, inverse result though not significant was observed in premenopausal women. In conclusion, the results of this meta-analysis highlighted that obesity contributed to increased BC risk in a nonlinear dose-response manner in postmenopausal women, and it is important to realize that body weight control may be a crucial process to reduce BC susceptibility.

Anthropometric factors and ovarian cancer risk: a systematic review and nonlinear dose-response meta-analysis of prospective studies

In the World Cancer Research Fund/American Institute for Cancer Research report from 2007 the evidence relating body fatness to ovarian cancer risk was considered inconclusive, while the evidence supported a probably causal relationship between adult attained height and increased risk. Several additional cohort studies have since been published, and therefore we conducted an updated meta-analysis of the evidence as part of the Continuous Update Project. We searched PubMed and several other databases up to 20th of August 2014. Summary relative risks (RRs) were calculated using a random effects model. The summary relative risk for a 5-U increment in BMI was 1.07 (95% CI: 1.03-1.11, I(2) = 54%, n = 28 studies). There was evidence of a nonlinear association, pnonlinearity  < 0.0001, with risk increasing significantly from BMI∼28 and above. The summary RR per 5 U increase in BMI in early adulthood was 1.12 (95% CI: 1.05-1.20, I(2) = 0%, pheterogeneity = 0.54, n = 6), per 5 kg increase in body weight was 1.03 (95% CI: 1.02-1.05, I(2) = 0%, n = 4) and per 10 cm increase in waist circumference was 1.06 (95% CI: 1.00-1.12, I(2) = 0%, n = 6). No association was found for weight gain, hip circumference or waist-to-hip ratio. The summary RR per 10 cm increase in height was 1.16 (95% CI: 1.11-1.21, I(2) = 32%, n = 16). In conclusion, greater body fatness as measured by body mass index and weight are positively associated risk of ovarian cancer, and in addition, greater height is associated with increased risk. Further studies are needed to clarify whether abdominal fatness and weight gain is associated with risk.

Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5·24 million UK adults

BACKGROUND

High body-mass index (BMI) predisposes to several site-specific cancers, but a large-scale systematic and detailed characterisation of patterns of risk across all common cancers adjusted for potential confounders has not previously been undertaken. We aimed to investigate the links between BMI and the most common site-specific cancers.

METHODS

With primary care data from individuals in the Clinical Practice Research Datalink with BMI data, we fitted Cox models to investigate associations between BMI and 22 of the most common cancers, adjusting for potential confounders. We fitted linear then non-linear (spline) models; investigated effect modification by sex, menopausal status, smoking, and age; and calculated population effects.

FINDINGS

5·24 million individuals were included; 166,955 developed cancers of interest. BMI was associated with 17 of 22 cancers, but effects varied substantially by site. Each 5 kg/m(2) increase in BMI was roughly linearly associated with cancers of the uterus (hazard ratio [HR] 1·62, 99% CI 1·56-1·69; p<0·0001), gallbladder (1·31, 1·12-1·52; p<0·0001), kidney (1·25, 1·17-1·33; p<0·0001), cervix (1·10, 1·03-1·17; p=0·00035), thyroid (1·09, 1·00-1·19; p=0·0088), and leukaemia (1·09, 1·05-1·13; p≤0·0001). BMI was positively associated with liver (1·19, 1·12-1·27), colon (1·10, 1·07-1·13), ovarian (1·09, 1.04-1.14), and postmenopausal breast cancers (1·05, 1·03-1·07) overall (all p<0·0001), but these effects varied by underlying BMI or individual-level characteristics. We estimated inverse associations with prostate and premenopausal breast cancer risk, both overall (prostate 0·98, 0·95-1·00; premenopausal breast cancer 0·89, 0·86-0·92) and in never-smokers (prostate 0·96, 0·93-0·99; premenopausal breast cancer 0·89, 0·85-0·94). By contrast, for lung and oral cavity cancer, we observed no association in never smokers (lung 0·99, 0·93-1·05; oral cavity 1·07, 0·91-1·26): inverse associations overall were driven by current smokers and ex-smokers, probably because of residual confounding by smoking amount. Assuming causality, 41% of uterine and 10% or more of gallbladder, kidney, liver, and colon cancers could be attributable to excess weight. We estimated that a 1 kg/m(2) population-wide increase in BMI would result in 3790 additional annual UK patients developing one of the ten cancers positively associated with BMI.

INTERPRETATION

BMI is associated with cancer risk, with substantial population-level effects. The heterogeneity in the effects suggests that different mechanisms are associated with different cancer sites and different patient subgroups.

FUNDING

National Institute for Health Research, Wellcome Trust, and Medical Research Council.

Body mass index and biliary tract disease: a systematic review and meta-analysis of prospective studies

OBJECTIVE

To evaluate the association between body mass index (BMI, kg/m(2)) and incidence of biliary tract disease.

METHODS

We performed a systematic review and a meta-analysis of prospective studies by searching the database of PubMed and EMBASE published up to December 31, 2013. Outcome of interest was disease of biliary tract system (gallbladder, extrahepatic bile duct and Ampullar of Vater). We used a random-effects model to combine the study-specific relative risks (RRs) and 95% confidence intervals (95% CIs) from 22 prospective studies. We examined whether BMI was associated with a higher risk of biliary tract disease in a combined analysis.

RESULTS

The positive association was stronger for non-cancer biliary tract disease than biliary tract cancer; combined RRs (95% CIs) comparing the top with bottom categories were 1.40 (1.15-1.65) for biliary tract cancer and 2.75 (2.35-3.15) for non-cancer biliary tract disease (P for difference<0.001). For non-cancer biliary tract disease, combined RRs (95% CIs) comparing the top with bottom categories were 3.21 (2.48-3.93) for women and 2.01 (1.66-2.37) for men (P for difference=0.04).

CONCLUSION

Obesity is associated with higher risks of biliary tract cancer and, to a greater extent, non-cancer biliary tract disease.

BMI and Breast Cancer in Korean Women: A Meta-Analysis

INTRODUCTION

The number of breast cancer women has increased dramatically in Korea. The cause is perceived to stem from adaptation to a westernized life style which increases body mass index (BMI). However, there are no meta-analysis data available that could help in understanding the relationship between Korean females' BMI and breast cancer occurrence.

METHOD

All the published articles that investigated the relationship of Korean women's BMI with breast cancer prevalence between 1950 and 2007 were included in this study, based on a screen of the comput- erized databases that search for these articles (MEDLINE, RISS4U and KMBase). The commercial software Comprehensive Meta Analysis was used for the analysis.

RESULTS

The high BMI score group presented a higher prevalence of breast cancer on both a fixed-effects model [odds ratio (OR) = 1.282; 95% confidence interval (CI) = 1.209, 1.361] and a random-effects model (OR = 1.388; 95% CI = 1.129, 1.706). In addition, a high BMI score on pre- and postmenopausal groups was found to have a significantly higher prevalence of breast cancer on both a fixed-effects model (OR = 1.467; 95% CI = 1.268, 1.698, OR = 1.614; 95% CI = 1.360, 1.917, pre- and postmenopausal, respectively) and a random-effects model (OR = 1.387; 95% CI = 1.134, 1.696, OR = 1.681; 95% CI = 1.149, 2.461, pre- and postmenopausal, respectively).

CONCLUSION

This meta-analysis of Korean women showed that a high BMI was related to a higher inci- dence rate of breast cancer. This study used a subgroup analysis of pre- and postmenopausal groups; the high BMI subset in both the pre- and postmenopausal groups was shown to have a higher incidence rate of breast cancer. [Asian Nursing Research 2009;3(1):31-40].