Sleep duration and endometrial cancer risk

Night shift work, sleep duration and endometrial cancer risk: A pooled analysis from the Epidemiology of Endometrial Cancer Consortium (E2C2)

Data on the role of circadian related factors in the etiology of endometrial cancer are scarce. We collected individual data on night shift work or daily sleep duration from 7,207 cases and 22,027 controls participating in 11 studies from the Epidemiology of Endometrial Cancer Consortium (E2C2). Main analyses were performed among postmenopausal women: 6,335 endometrial cancer cases and 18,453 controls. Using individual data, study-specific odd ratios (ORs) and their corresponding 95% confidence intervals (CIs) were estimated with logistic regression and pooled analyses were conducted using random-effects meta-analyses. A non-significant inverse association was observed between endometrial cancer and night shift work (OR=0.89, 95%CI=0.72-1.09; I2=0.0%, Pheterogeneity=0.676). Associations did not vary by shift type (permanent or rotating), or duration of night work. Categorizations of short (<7h) or long (≥9h) sleep duration were not associated with endometrial cancer risk (ORshort=1.02, 95%CI=0.95-1.10; I2=55.3%, Pheterogeneity=0.022; ORlong=0.93, 95%CI=0.81-1.06; I2=11.5%, Pheterogeneity=0.339). No associations were observed per 1-h increment of sleep (OR=0.98, 95%CI=0.95-1.01; I2=46.1%, Pheterogeneity=0.063), but an inverse association was identified among obese women (OR=0.93, 95%CI=0.89-0.98 per 1-h increment; I2=12.7%, Pheterogeneity=0.329). Overall, these pooled analyses provide evidence that night shift work and sleep duration are not strong risk factors for endometrial cancer in postmenopausal women.

Sleep duration and the risk of endometrial cancer incidence among Japanese women: A pooled analysis of the Miyagi Cohort Study and the Ohsaki Cohort Study

OBJECTIVE

Endometrial cancer has been increasing worldwide, and is one of the most common female hormone-related cancers. The purpose of this study was to examine the association between sleep duration and risk of endometrial cancer among Japanese women.

METHODS

We conducted a pooled analysis of two prospective studies conducted among residents of Miyagi Prefecture in rural northern Japan. A total of 36,537 women aged 40-79 years participated in the Miyagi Cohort Study in 1990 and in the Ohsaki Cohort Study in 1994. The participants responded to a self-administered questionnaire that including sleep duration. Sleep duration was assessed at the baseline using a self-administered questionnaire. The participants entered the mean integer number representing the hours of sleep taken per day during the previous year. We divided the participants into three groups (≤6 h, 7-8 h, or ≥9 h). Cox proportional hazards regression analysis was used to estimate the multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for endometrial cancer incidence.

RESULTS

During 745,993 person-years of follow-up, we identified 146 incident cases of endometrial cancer. Compared with women who slept 7-8 h per day, the multivariate HR (95%CI) for endometrial cancer incidence was 1.07 (0.72-1.60) for those who slept 6 h or less, and 1.05 (0.57-1.93) for those who slept 9 h or longer (p-trend=0.57).

CONCLUSION

In analysis of two population -based prospective cohort studies conducted among Japanese women, we found no significant associations between sleep duration and the incidence of endometrial cancer.

Sleep and cancer recurrence and survival in patients with resected Stage III colon cancer: findings from CALGB/SWOG 80702 (Alliance)

BACKGROUND

We sought to assess the influences of sleep duration, sleep adequacy, and daytime sleepiness on survival outcomes among Stage III colon cancer patients.

METHODS

We conducted a prospective observational study of 1175 Stage III colon cancer patients enrolled in the CALGB/SWOG 80702 randomised adjuvant chemotherapy trial who completed a self-reported questionnaire on dietary and lifestyle habits 14-16 months post-randomisation. The primary endpoint was disease-free survival (DFS), and secondary was overall survival (OS). Multivariate analyses were adjusted for baseline sociodemographic, clinical, dietary and lifestyle factors.

RESULTS

Patients sleeping ≥9 h-relative to 7 h-experienced a worse hazard ratio (HR) of 1.62 (95% confidence interval (CI), 1.01-2.58) for DFS. In addition, those sleeping the least (≤5 h) or the most (≥ 9 h) experienced worse HRs for OS of 2.14 (95% CI, 1.14-4.03) and 2.34 (95% CI, 1.26-4.33), respectively. Self-reported sleep adequacy and daytime sleepiness showed no significant correlations with outcomes.

CONCLUSIONS

Among resected Stage III colon cancer patients who received uniform treatment and follow-up within a nationwide randomised clinical trial, very long and very short sleep durations were significantly associated with increased mortality. Interventions targeting optimising sleep health among indicated colon cancer patients may be an important method by which more comprehensive care can be delivered.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01150045.

Effect of sleep disorders on the risks of cancers and site-specific cancers

PURPOSE

Whether preexisting sleep disorder is an independent risk factor for cancer remains unclear. Therefore, we performed this propensity score-matched population-based cohort study to compare the incidence rate ratios (IRRs) of specific cancers between patients with and without sleep disorders.

PATIENTS AND METHODS

Patients were categorized into two groups on the basis of the presence or absence of sleep disorders and matched at a 1:1 ratio.

RESULTS

Propensity score matching yielded a final cohort of 289,162 patients (i.e., 144,581 and 144,581 in the sleep disorder and nonsleep disorder groups, respectively) who were eligible for further analysis. In multivariate Cox regression analysis, the adjusted hazard ratio (aHR; 95% confidence interval [CI]) of cancer risk in the sleep disorder group compared with the nonsleep disorder group was 1.07 (1.04-1.12; P = 0.0001). Furthermore, the adjusted IRRs (95% CIs) for all cancers, breast cancer, and ovarian cancer in the patients with sleep disorders were 1.08 (1.02-1.18), 1.20 (1.08-1.32), and 1.30 (1.10-1.52), respectively.

CONCLUSION

The results suggested that sleep disorders are a significant risk factor for all cancers, breast cancer, and ovarian cancer.

Integrative Approaches to the Treatment of Cancer

A significant proportion of cancer patients use forms of complementary medicine or therapies. An integrative approach to cancer management combines conventional medicine with evidence-based complementary medicines/therapies and lifestyle interventions, for the treatment and prevention of disease and the optimisation of health. Its basis is a holistic one; to treat the whole person, not just the disease. It makes use of adjunct technologies which may assist the clinician in diagnosis of early carcinogenesis and monitoring of treatment effectiveness. Many factors contribute to the development of cancer including some which are largely modifiable by the patient and which oncologists may be in a position to advise on, such as stress, poor nutrition, lack of physical activity, poor sleep, and Vitamin D deficiency. An integrative approach to addressing these factors may contribute to better overall health of the patient and better outcomes. Evidence-based complementary medicine approaches include the use of supplements, herbal medicine, various practices that reduce stress, and physical therapies. Individualised to the patient, these can also help address the symptoms and signs associated with cancer and its orthodox treatment.

Night work, chronotype and risk of endometrial cancer in the Screenwide case-control study

BACKGROUND

Circadian disruption caused by night work has been associated with hormonal-related cancers such as breast and prostate cancer. Data on the role of circadian factors in the aetiology of endometrial cancer, an oestrogen-associated cancer, are scarce.

METHODS

We examined the association between endometrial cancer and night shift work, chronotype (a characteristic correlating with preference for morning or evening activity) and sleep duration, in 180 incident cases and 218 hospital controls. Participants were interviewed face-to-face by trained interviewers to collect information on sociodemographic factors, familial, medical, occupational history (including work shifts), sleep duration and chronotype, and other lifestyle factors. We used logistic regression models adjusted for potential confounders to estimate ORs and 95% CIs.

RESULTS

After adjustment by potential confounders, we found an inverse not statistically significant association between ever worked in night shifts and endometrial cancer (OR=0.64; 95% CI=0.35 to 1.16). Associations were irrespective of shift type (permanent or rotating nights) or duration of night work. We did not observe any statistically significant association between endometrial cancer and sleep duration, while inconsistent patterns were observed for chronotype and endometrial cancer risk.

CONCLUSIONS

These data do not support a role for circadian disruption in the carcinogenesis of endometrial cancer.

Chronotype and risk of post-menopausal endometrial cancer in the California Teachers Study

Working at night causes circadian disruption and it has been classified as a probable carcinogen. An evening chronotype, or preference for late day activity, has been shown to increase risk for several adverse health effects, such as metabolic disorders and recently, breast cancer. To further explore this emerging area of interest, we examined the association between endometrial cancer (EC) risk, another common cancer in women, and chronotype. The women in this study were members of the California Teachers Study cohort, which was established in 1995. Chronotype was reported on a subsequent questionnaire (Q5), administered in 2012-2013. The women included in this analysis were under age 90 years, were post-menopausal at Q5, and had no hysterectomy. The cancer cases, identified through linkages to the California Cancer Registry, were diagnosed between 1996 and 2014. We used unconditional logistic regression models to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of the associations between chronotype and EC diagnosis. There were 437 EC cases and 26,753 cancer-free controls included in this analysis. Controls were more likely to classify themselves as current morning chronotypes than were cases (39% and 34%, respectively). Compared to morning types, women who were definite evening types had a statistically significantly elevated OR of 1.44 (95% CI 1.09-1.91). This association was more pronounced among obese women as compared to non-obese women. For evening type compared to morning type, the OR among obese women was 2.01 (95% CI 1.23, 3.29) while the OR for non-obese women was 1.12 (95% CI 0.77, 1.63). To our knowledge, the association between EC risk and evening chronotype has not been previously reported, but is consistent with the small body of literature which suggests increased breast cancer risks among evening chronotypes. Because this study was based on a retrospective analysis in a cohort of mostly white female teachers in California, further analysis of chronotype as a potential EC risk factor should be considered in other cohorts and in prospective analyses in order to further explore this relationship.

Melatonin and its mechanism of action in the female reproductive system and related malignancies

Melatonin (N-acetyl-5-methoxytryptamine), the main product of pineal gland in vertebrates, is well known for its multifunctional role which has great influences on the reproductive system. Recent studies documented that melatonin is a powerful free radical scavenger that affects the reproductive system function and female infertility by MT1 and MT2 receptors. Furthermore, cancer researches indicate the influence of melatonin on the modulation of tumor cell signaling pathways resulting in growth inhibitor of the both in vivo/in vitro models. Cancer adjuvant therapy can also benefit from melatonin through therapeutic impact and decreasing the side effects of radiation and chemotherapy. This article reviews the scientific evidence about the influence of melatonin and its mechanism of action on the fertility potential, physiological alteration, and anticancer efficacy, during experimental and clinical studies.

Differential Gene Expression in Brain and Liver Tissue of Wistar Rats after Rapid Eye Movement Sleep Deprivation

Sleep is essential for the survival of most living beings. Numerous researchers have identified a series of genes that are thought to regulate "sleep-state" or the "deprived state". As sleep has a significant effect on physiology, we believe that lack of total sleep, or particularly rapid eye movement (REM) sleep, for a prolonged period would have a profound impact on various body tissues. Therefore, using the microarray method, we sought to determine which genes and processes are affected in the brain and liver of rats following nine days of REM sleep deprivation. Our findings showed that REM sleep deprivation affected a total of 652 genes in the brain and 426 genes in the liver. Only 23 genes were affected commonly, 10 oppositely, and 13 similarly across brain and liver tissue. Our results suggest that nine-day REM sleep deprivation differentially affects genes and processes in the brain and liver of rats.

The association between sleep duration and prostate cancer: A systematic review and meta-analysis

The association between sleep duration and prostate cancer (PCa) risk is still unclear. We performed a systematic review and meta-analysis to explore if sleep duration is associated with PCa in men.A comprehensive literature search was conducted in November 2019 based on the Pubmed, Embase, and Cochrane databases. After extracting the data, the random effects model was used to calculate the pooled Risk Ratio (RR) and it's 95% confidence interval (CI) to represent the correlation between sleep duration and PCa risk.Overall, we included 6 studies in our meta-analysis. Our pooled results showed that neither short sleep (RR = 0.99; 95%CI:0.91-1.07, P = .74) nor long sleep (RR = 0.88; 95%CI:0.75-1.04, P = .15) was associated with the risk of PCa.Sleep duration has no significant effect on PCa risk. Long sleep may have a potential protective effect on PCa incidence.

Melatonin activates cell death programs for the suppression of uterine leiomyoma cell proliferation

The circadian nature of melatonin has a protective effect on the progression of female reproductive cancers, including breast and ovarian cancers. However, the effect of melatonin on the growth of uterine leiomyoma is still unclear. In this study, we found that the growth of uterine leiomyoma ELT3 cells was reduced by treatment with melatonin. Treatment with melatonin increased the distribution of sub-G1 phase and increased DNA condensation in ELT3 cells. Melatonin-induced apoptosis and autophagy cell death progression were observed in ELT3 cells. Melatonin exerts a highly selective effect on primary normal human uterine smooth muscle (UtSMC) cells. The UtSMC cell cycle was arrested by melatonin treatment through up-regulation of p21, p27, and PTEN protein expression, but melatonin did not further promote apoptosis program activation. Melatonin reduced cell proliferation in ELT3 cells underlying the activation of melatonin MT1 and MT2 receptors, which in turn down-regulated the Akt-ERK1/2-NFκB signaling pathway. Melatonin reduced ELT3 tumor growth in both xenograft and orthotopic uterine tumor mice models. The extracellular matrix of the tumor was also reduced by melatonin treatment. Taken together, these results suggest that melatonin potentially plays a role in suppression of uterine leiomyoma growth.

Sleep duration and the risk of cancer: a systematic review and meta-analysis including dose-response relationship

Background

The effect of sleep duration on cancer risk remains controversial. We aimed to quantify the available evidence on this relationship using categorical and dose–response meta-analyses.

Methods

Population-based cohort studies and case-control studies with at least three categories of sleep duration were identified by searching PubMed, EMBASE, and the Cochrane Library database up to July 2017.

Results

Sixty-five studies from 25 articles were included, involving 1,550,524 participants and 86,201 cancer cases. The categorical meta-analysis revealed that neither short nor long sleep duration was associated with increased cancer risk (short: odds ratio [OR] = 1.01, 95% confidence intervals [CI] = 0.97–1.05; long: OR = 1.02, 95% CI = 0.97–1.07). Subgroup analysis revealed that short sleep duration was associated with cancer risk among Asians (OR = 1.36; 95% CI: 1.02–1.80) and long sleep duration significantly increased the risk of colorectal cancer (OR = 1.21; 95% CI: 1.08–1.34). The dose–response meta-analysis showed no significant relationship between sleep duration and cancer risk. When treated as two linear piecewise functions with a cut point of 7 h, similar nonsignificant associations were found (per 1-h reduction: OR = 1.02, 95% CI = 0.98–1.07; per 1-h increment: OR = 1.003, 95% CI = 0.97–1.03).

Conclusion

Categorical meta-analysis indicated that short sleep duration increased cancer risk in Asians and long sleep duration increased the risk of colorectal cancer, but these findings were not consistent in the dose–response meta-analysis. Long-term randomized controlled trials and well-designed prospective studies are needed to establish causality and to elucidate the mechanism underlying the association between sleep duration and cancer risk.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5025-y) contains supplementary material, which is available to authorized users.

Cadmium exposure and endometrial cancer risk: A large midwestern U.S. population-based case-control study

Estrogen-mimicking chemicals, such as cadmium, may be associated with increased susceptibility to hormone-dependent cancers, though supporting data are sparse, particularly for endometrial cancer. The Health and Environmental Exposure Research (HEER) study worked with the Arkansas Central Cancer Registry, Iowa Cancer Registry and Missouri Cancer Registry to obtain names of women diagnosed with endometrial cancer who were willing to be contacted for participation in our case control study. Voter registration lists from Iowa and Missouri were used to randomly select similarly aged women as represented in the case population. Participants were interviewed by telephone to obtain information on known or suspected endometrial risk factors. Urine kits were sent to participants for home collection and returned for analysis. Our case-control study consisted of 631 incident cases of endometrial cancer diagnosed from January 2010 to October 2012 and 879 age-matched population-based controls, ages 18-81 years (mean age 65 years). We quantified cadmium amounts in urine and standardized these values through creatinine adjustment. Using data from all survey completers, we developed a multivariable model for endometrial cancer. Creatinine-adjusted cadmium concentration was added to this model. Odds ratio (OR) and 95% confidence intervals (CIs) for endometrial cancer were calculated. After multivariable adjustment, higher creatinine-adjusted cadmium exposure was associated with a statistically significant increase of endometrial cancer risk (OR: 1.22; 95% CI: 1.03-1.44). Our results provide evidence that cadmium may increase the risk of endometrial cancer, possibly through estrogenic effects.

Sleep and survival among women with breast cancer: 30 years of follow-up within the Nurses' Health Study

BACKGROUND

Breast cancer is a leading cause of cancer death in women. Sleep has been linked with mortality among cancer-free population; however, its association with survival among women with breast cancer is understudied.

METHODS

Breast cancer patients (N=3682) reported their average sleep duration post diagnosis. Subsamples also provided their pre-diagnosis sleep duration (n=1949) and post-diagnosis sleep difficulties (n=1353). Multivariate Cox models estimated hazard ratios (HR) and confidence intervals (CI) of all-cause, breast cancer, and non-breast cancer mortality.

RESULTS

At diagnosis, the mean age was 64.9 years and 91.7% were stage I or II. Women sleeping ⩾9 h per night post diagnosis had a strong higher risk of all-cause (multivariate HRs: MV-HR=1.37, CI=1.10-1.71), breast cancer (MV-HR=1.46, CI=1.02-2.07), and non-breast cancer mortality (MV-HR=1.34, CI=1.01-1.79), compared to women sleeping 8 h per night. Increased sleep duration post diagnosis (vs unchanged) and regular sleep difficulties (vs rare/none) were associated with a strong elevated risk of all-cause mortality (MV-HRincreased duration=1.35, CI=1.04-1.74; MV-HRregular difficulties=1.49, CI=1.02-2.19) and a moderate greater risk of breast cancer and non-breast cancer mortality.

CONCLUSIONS

Various facets of sleep were associated with higher all-cause mortality risk. If replicated, these findings support evaluation of breast cancer patients' sleep duration and difficulties to identify those at risk for poorer outcomes.

Dietary Sources and Bioactivities of Melatonin

Insomnia is a serious worldwide health threat, affecting nearly one third of the general population. Melatonin has been reported to improve sleep efficiency and it was found that eating melatonin-rich foods could assist sleep. During the last decades, melatonin has been widely identified and qualified in various foods from fungi to animals and plants. Eggs and fish are higher melatonin-containing food groups in animal foods, whereas in plant foods, nuts are with the highest content of melatonin. Some kinds of mushrooms, cereals and germinated legumes or seeds are also good dietary sources of melatonin. It has been proved that the melatonin concentration in human serum could significantly increase after the consumption of melatonin containing food. Furthermore, studies show that melatonin exhibits many bioactivities, such as antioxidant activity, anti-inflammatory characteristics, boosting immunity, anticancer activity, cardiovascular protection, anti-diabetic, anti-obese, neuroprotective and anti-aging activity. This review summaries the dietary sources and bioactivities of melatonin, with special attention paid to the mechanisms of action.

Sleep Duration and Cancer in the NIH-AARP Diet and Health Study Cohort

Background

Very few studies have examined sleep duration in relation to cancer incidence with the exception of breast cancer.

Methods

We assessed the associations between sleep duration and incidences of total and 18 site-specific cancers in the NIH-AARP Health and Diet Study cohort, with 173,327 men and 123,858 women aged 51–72 years at baseline. Self-reported sleep duration categories were assessed via questionnaire. We used multivariable Cox proportional hazards regression to estimate hazard ratios (HR) and 95% confidence intervals (CI), using 7–8 hours/night as the reference.

Results

We observed a significantly increased risk of stomach cancer among male short sleepers (multivariable HR_{5-6 vs. 7–8 hours} = 1.29; 95%CI: 1.05, 1.59; P_trend = 0.03). We also observed suggestive associations in either short or long sleepers, which did not reach overall significance (P_trend >0.05), including increased risks in male short sleepers for cancers of head and neck (HR_{<5vs.7-8 hours} = 1.39; 95%CI:1.00–1.95), bladder (HR_{5-6vs.7-8 hours} = 1.10; 95%CI:1.00–1.20), thyroid (HR_{<5 vs. 7–8 hours} = 2.30; 95%CI:1.06, 5.02), Non-Hodgkin Lymphoma (NHL) (HR_{5-6vs.7-8 hours} = 1.17; 95%CI:1.02–1.33), and myeloma (HR_{<5vs.7-8 hours} = 2.06; 95%CI:1.20–3.51). In women, the suggestive associations include a decreased total cancer risk (HR_{<5vs.7-8 hours} = 0.9; 95%CI:0.83–0.99) and breast cancer risk (HR_{<5vs.7-8 hours} = 0.84; 95%CI:0.71–0.98) among short sleepers. A decreased ovarian cancer risk (HR_{≥ 9 vs. 7–8 hours} = 0.50; 95%CI:0.26–0.97) and an increased NHL risk (HR_{≥ 9 vs. 7–8 hours} = 1.45; 95%CI:1.00–2.11) were observed among long sleepers.

Conclusion

In an older population, we observed an increased stomach cancer risk in male short sleepers and suggestive associations with short or long sleep duration for many cancer risks in both genders.

Pre-diagnostic Sleep Duration and Sleep Quality in Relation to Subsequent Cancer Survival

STUDY OBJECTIVES

Poor sleep quality and short sleep duration have been associated with elevated risk for several cancer types; however, the relationship between sleep and cancer outcomes has not been well characterized. We assessed the association between pre-diagnostic sleep attributes and subsequent cancer survival within the Women's Health Initiative (WHI).

METHODS

We identified WHI participants in whom a first primary invasive cancer had been diagnosed during follow-up (n = 21,230). Participants provided information on sleep characteristics at enrollment. Cox regression was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between these pre-diagnostic sleep characteristics and cancer-specific survival for all cancers combined and separately for common cancers. Analyses were adjusted for age, study arm, cancer site, marital status, income, smoking, physical activity, and time to diagnosis.

RESULTS

No individual pre-diagnostic sleep characteristics were found to be significantly associated with cancer survival in analyses of all cancer sites combined; however, women who reported short sleep duration (≤ 6 h sleep/night) combined with frequent snoring (≥ 5 nights/w experienced significantly poorer cancer-specific survival than those who reported 7-8 h of sleep/night and no snoring (HR = 1.32, 95% CI: 1.14-1.54). Short sleep duration (HR = 1.46, 95% CI: 1.07-1.99) and frequent snoring (HR = 1.34, 95% CI: 0.98-1.85) were each associated with poorer breast cancer survival; those reporting short sleep combined with frequent snoring combined had substantially poorer breast cancer survival than those reporting neither (HR = 2.14, 95% CI: 1.47-3.13).

CONCLUSIONS

Short sleep duration combined with frequent snoring reported prior to cancer diagnosis may influence subsequent cancer survival, particularly breast cancer survival.

Sleep duration and cancer risk in women

PURPOSE

The objective was to conduct an analysis of sleep duration and risk of selected site-specific and groups of cancer among a large prospective cohort of California women.

METHODS

The study population was comprised of 101,609 adult females participating in the California Teachers Study. All sites of invasive cancer prospectively diagnosed from baseline (1995-1996) through 2011 were identified through linkage to the California Cancer Registry (n = 12,322). Site-specific analyses focused on the following cancers: breast (n = 5,053), colorectal (n = 983), lung (n = 820), melanoma (n = 749), and endometrial (n = 957). Additionally, we evaluated a group of estrogen-mediated cancers consisting of breast, endometrial, and ovarian cancer (n = 6,458). Sleep duration was based on self-report of average time sleeping in the year prior to baseline. Cox proportional hazard models were used to calculate adjusted hazard ratios and 95 % confidence intervals (HRs, 95 % CI).

RESULTS

Point estimates for all sites and site-specific cancers generally were near or below one for short sleepers (<6 h/night) and above one for long sleepers (10+ h/night); confidence intervals, however, were wide and included unity. Compared to average sleepers (7-9 h/night), long sleepers had an increased risk of the group of estrogen-mediated cancers (HR 1.22, 95 % CI 0.97-1.54, p (trend) = 0.04).

CONCLUSIONS

These analyses suggest that longer sleep may be associated with increased risks of estrogen-mediated cancers. Further studies with more refined measures of sleep duration and quality are warranted.

Sleep duration and cancer risk: a systematic review and meta-analysis of prospective studies

To assess the risk of cancers associated with sleep duration using a meta-analysis of published cohort studies, we performed a comprehensive search using PubMed, Embase and Web of Science through October 2013. We combined hazard ratios (HRs) from individual studies using meta-analysis approaches. A random effect dose-response analysis was used to evaluate the relationship between sleep duration and cancer risk. Subgroup analyses and sensitivity analyses were also performed. Publication bias was evaluated using Funnel plots and Begg's test. A total of 13 cohorts from 12 studies were included in this meta-analysis, which included 723,337 participants with 15,156 reported cancer outcomes during a follow-up period ranging from 7.5 to 22 years. The pooled adjusted HRs were 1.06 (95% CI: 0.92, 1.23; P for heterogeneity=0.003) for short sleep duration, 0.91 (95% CI: 0.78, 1.07; P for heterogeneity <0.0001) for long sleep duration. In subgroup analyses stratified by cancer type, long duration of sleep showed an inverse relation with hormone-related cancer (HR=0.79; 95% CI: 0.65, 0.97; P for heterogeneity=0.009) and a greater risk of colorectal cancer (HR=1.29; 95% CI: 1.09, 1.52; P for heterogeneity=0.346). Further meta-analysis on dose-response relationships showed that the relative risks of cancer were 1.00 (95% CI: 0.99, 1.01; P for linear trend=0.9151) for one hour of sleep increment per day, and 1.00 (95% CI: 0.98, 1.01; P for linear trend=0.7749) for one hour of sleep increment per night. No significant dose-response relationship between sleep duration and cancer was found on non-linearity testing (P=0.5053). Our meta-analysis suggests a positive association between long sleep duration and colorectal cancer, and an inverse association with incidence of hormone related cancers like those in the breast. Studies with larger sample size, longer follow-up times, more cancer types and detailed measure of sleep duration are warranted to confirm these results.

Association between sleep and breast cancer incidence among postmenopausal women in the Women's Health Initiative

STUDY OBJECTIVES

To determine whether the duration of sleep, sleep quality, insomnia, or sleep disturbance was associated with incident breast cancer in the Women's Health Initiative (WHI).

DESIGN

Prospective cohort study.

SETTING

Women enrolled in one of the Clinical Trial (CT) arms or the Observational Study (OS) from the WHI conducted in the United States.

PARTICIPANTS

This study included 110,011 women age 50 to 79 years with no history of cancer.

MEASUREMENTS AND RESULTS

Typical sleep duration, sleep quality, and other self-reported sleep measures over the past 4 weeks were assessed during the screening visits for both the CT and OS participants. The presence of insomnia and level of sleep disturbance was calculated from an index of the WHI Insomnia Rating Scale. The outcome for this study was primary, invasive breast cancer. A total of 5,149 incident cases of breast cancer were identified in this study. No statistically significant associations were found between sleep duration, sleep quality, insomnia, or level of sleep disturbance with the risk of breast cancer after multivariable adjustment. A positive trend was observed for increasing sleeping duration with the risk of estrogen receptor positive breast cancer, but the association estimates for each sleep duration category were weak and nonsignificant.

CONCLUSIONS

This study does not provide strong support for an association between self-reported sleep duration, sleep quality, insomnia, or sleep disturbance with the risk of breast cancer.

Update on the role of melatonin in the prevention of cancer tumorigenesis and in the management of cancer correlates, such as sleep-wake and mood disturbances: review and remarks

The aim of this article was to perform a systematic review on the role of melatonin in the prevention of cancer tumorigenesis--in vivo and in vitro--as well as in the management of cancer correlates, such as sleep-wake and mood disturbances. The International Agency for Research on Cancer recently classified "shift-work that involves circadian disruption" as "probably carcinogenic to humans" (Group 2A) based on "limited evidence in humans for the carcinogenicity of shift-work that involves night-work", and "sufficient evidence in experimental animals for the carcinogenicity of light during the daily dark period (biological night)". The clinical implications and the potential uses of melatonin in terms of biologic clock influence (e.g. sleep and mood), immune function, cancer initiation and growth, as well as the correlation between melatonin levels and cancer risk, are hereinafter recorded and summarized. Additionally, this paper includes a description of the newly discovered effects that melatonin has on the management of sleep-wake and mood disturbances as well as with regard to cancer patients' life quality. In cancer patients depression and insomnia are frequent and serious comorbid conditions which definitely require a special attention. The data presented in this review encourage the performance of new clinical trials to investigate the possible use of melatonin in cancer patients suffering from sleep-wake and mood disturbances, also considering that melatonin registered a low toxicity in cancer patients.

Sleep duration and breast cancer risk: a meta-analysis of observational studies

Studies on the association of short or long sleep duration with breast cancer risk have reported inconsistent results. We quantitatively assessed this association by conducting a meta-analysis based on the evidence from observational studies. In April 2013, we performed electronic searches in PubMed, EmBase and the Cochrane Library to identify studies examining the effect of sleep duration on breast cancer incidence. The odds ratio (OR) was used to measure any such association in a random-effects model. The analysis was further stratified by confounding factors that could bias the results. A total of six studies (two case-control and four cohort studies) involving 159,837 individuals were included in our meta-analysis. Our study did not show an association between either short or long sleep duration and breast cancer risk (short sleep duration data: pooled OR = 1.01, 95% confidence interval (CI) = 0.90-1.14, p = 0.853; long sleep duration data: pooled OR = 0.95, 95% CI = 0.86-1.04, p = 0.251). Moreover, we did not identify any statistically significant association between sleep duration and breast cancer risk in all the subgroup analyses. In conclusion, our findings indicate that sleep duration has no effect on breast cancer risk.

Association between sleep duration and cancer risk: a meta-analysis of prospective cohort studies

BACKGROUND

Sleep duration has been shown to play an important role in the development of cancer. However, the results have been inconsistent. A meta-analysis with prospective cohort studies was performed to clarify the association between short or long sleep duration and cancer risk.

METHODS

PubMed and Embase databases were searched for eligible publications. Pooled relative risk (RR) with 95% confidence interval (CI) was calculated using random- or fixed- model.

RESULTS

A total of 10 prospective studies (8392 incident cases and 555678 participants) were included in the meta-analysis. Neither short nor long sleep duration was statistically associated with increased risk of cancer (short sleep duration: RR=1.05, 95%CI=0.90-1.24, p=0.523; long sleep duration: RR=0.92, 95%CI=0.76-1.12, p=0.415). In the subgroup by cancer type, long sleep duration was positively associated with colorectal cancer (RR=1.29, 95%CI=1.09-1.52, p=0.003).

CONCLUSION

The present meta-analysis suggested that neither short nor long sleep duration was significantly associated with risk of cancer, although long sleep duration increased risk of with colorectal cancer. Large-scale well-design prospective studies are required to be conducted to further investigate the observed association.

Sleep duration and incidence of colorectal cancer in postmenopausal women

Background:

Sleep duration is dependent on circadian rhythm that controls a variety of key cellular functions. Circadian disruption has been implicated in colorectal tumorigenesis in experimental studies. We prospectively examined the association between sleep duration and risk of colorectal cancer (CRC).

Methods:

In the Women’s Health Initiative Observational Study, 75 828 postmenopausal women reported habitual sleep duration at baseline 1993–1998. We used Cox proportional hazards regression model to estimate the hazard ratio (HR) of CRC and its associated 95% confidence interval (CI).

Results:

We ascertained 851 incident cases of CRC through 2010, with an average 11.3 years of follow-up. Compared with 7 h of sleep, the HRs were 1.36 (95% CI 1.06–1.74) and 1.47 (95% CI 1.10–1.96) for short (⩽5 h) and long (⩾9 h) sleep duration, respectively, after adjusting for age, ethnicity, fatigue, hormone replacement therapy (HRT), physical activity, and waist to hip ratio. The association was modified by the use of HRT (P-interaction=0.03).

Conclusion:

Both extreme short and long sleep durations were associated with a moderate increase in the risk of CRC in postmenopausal women. Sleep duration may be a novel, independent, and potentially modifiable risk factor for CRC.