Physical activity and risk of breast cancer in premenopausal women

Physical activity from menarche-to-first pregnancy and risk of breast cancer: the California teachers study

PURPOSE

A longer menarche-to-first pregnancy window of susceptibility (WOS) is associated with increased breast cancer risk. Whether physical activity, an established preventive risk factor, during the menarche-to-first pregnancy WOS offsets breast cancer risk overall or for specific molecular subtypes is unclear.

METHODS

We examined the prospective association between physical activity during the menarche-to-first pregnancy WOS and breast cancer risk in the California Teachers Study (N = 78,940). Recreational physical activity at multiple timepoints were recalled at cohort entry, and converted to metabolic equivalent of task hours per week (MET-hrs/wk). We used multivariable Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

We observed 5,157 invasive breast cancer cases over 21.6 years of follow-up. Longer menarche-to-first pregnancy WOS (≥ 20 vs. < 15 years) was associated with higher breast cancer risk (HR = 1.23, 95% CI = 1.13-1.34). Women with higher physical activity level during menarche-to-first pregnancy had lower risk of invasive breast cancer (≥ 40 vs. < 9 MET-hrs/wk: HR = 0.89, 95% CI = 0.83-0.97) and triple-negative subtype (≥ 40 vs. < 9 MET-hrs/wk: HR = 0.53, 95% CI = 0.32-0.87). No association was observed for luminal A-like and luminal B-like subtypes. Higher physical activity level was associated with lower breast cancer risk among women with moderate (15-19 years) menarche-to-first pregnancy intervals (≥ 40 vs. < 9 MET-hrs/wk: HR = 0.80, 95% CI = 0.69-0.92), but not with short (< 15 years) or long (≥ 20 years) intervals.

CONCLUSION

Physical activity during a WOS was associated with lower breast cancer risk in our cohort. Understanding timing of physical activity throughout the life course in relationship with breast cancer risk maybe important for cancer prevention strategies.

Healthy Eating for Successful Living in Older Adults™ community education program—evaluation of lifestyle behaviors: A randomized controlled trial

Objective: Older adults face many chronic health issues including heart disease and osteoporosis, which are preventable through changes in lifestyle behaviors. The Healthy Eating for Successful Living in Older Adults™ (HESL) is a 6-week community education program designed specifically for persons aged ≥60 years, to promote behavioral changes toward a healthy lifestyle. Our objective is to evaluate the HESL. This is the first official evaluation of the HESL since its initiation in 2005.

Study Design: A cluster randomized controlled trial.

Method: Program implementation and evaluation took place between July 2018 and January 2020. Twenty-nine sites, with 292 participants aged ≥60 years from across five states (mostly from Massachusetts), were randomized into the intervention group (IG) (16 sites; n = 150 participants) and control group (CG) (13 sites; n = 142 participants). The HESL workshops followed a scripted curriculum including information from the USDA’s MyPlate™ and the USDA 2015–2020 dietary guidelines. Intervention elements included goal setting, self-assessment, group support, and problem solving through brainstorming. The CG received no intervention. Outcome measures were collected in both groups at baseline, 2 weeks postintervention (week 8), and 6 months postintervention. These included self-reported lifestyle behaviors, a composite healthy behavior index (HBI), body mass index [weight (kg)/height (m2)], and waist-to-hip circumference ratio (WHR). Mixed-effects regression models were used to examine the impact of the intervention.

Results: The IG showed significantly improved responses to most healthy lifestyle behavior questions at week 8 compared to the CG. However, not all improved responses were sustained at month 6. Significant improvements detected at month 6 included responses to the question on making food choices that are healthy for the heart, using MyPlate™ tools for food choices, reading nutrition labels when shopping/planning meals, and confidence in managing own health (p &lt; 0.001 in most cases). HBI was significantly improved at week 8 and month 6 (p &lt; 0.001). WHR decreased significantly (p &lt; 0.05) at month 6.

Conclusion: Positive changes in lifestyle behaviors and WHR were observed in older adults due to the HESL intervention.

Clinical Trial Registration:clinicaltrial.gov, Identifier: NCT04991844; https://clinicaltrials.gov/ct2/show/NCT04991844

Multivariate analysis of independent roles of socioeconomic status, occupational physical activity, reproductive factors, and postmenopausal hormonal therapy in risk of breast cancer

PURPOSE

This case-control study assesses the independent roles of reproductive history, postmenopausal hormonal therapy (HT), socioeconomic status (SES), and occupational physical activity on the risk of breast cancer (BC).

METHODS

Odds ratios (OR) were estimated from conditional logistic multivariate regression model in a data set of 19,253 Finnish women diagnosed with BC between 1994 and 2013 and 96,265 age-matched population controls.

RESULTS

Both pre- and postmenopausal white-collar workers had significantly increased risk of ductal and lobular BC as compared to manual workers. Moderate occupational physical activity reduced risk of lobular BC by 14%. There was a transient increase in the risk of BC observed after each birth followed by a protective effect starting some years after the delivery. As the number of children increased, the short-term excess risk was lower and protective effect was observed earlier. Continuous estrogen-progestin therapy (EPT) significantly increased the risk of both ductal and lobular BC and the magnitude of risk was directly proportional to duration of use (OR for 5+ years of use 2.26, 95% confidence interval 2.12-2.42). Monthly EPT for 5+ years increased the risk (OR 1.32, 95% CI 1.20-1.45). Users of estradiol plus levonorgestrel intrauterine system devices showed ORs of 1.56 (95% CI 1.45-1.69) and 2.18 (95% CI 1.81-2.64) for ductal and lobular BC, respectively.

CONCLUSION

This study concludes that pregnancy has a dual effect on BC risk, with a transient increase in risk followed by a long-term protective effect. The SES and HT have a large effect on BC risk while occupational physical activity has only a small independent effect.

Physical Activity and Long-Term Risk of Breast Cancer, Associations with Time in Life and Body Composition in the Prospective Malmö Diet and Cancer Study

Being physically active as part of everyday life reduces breast cancer risk. Less is known whether the benefits of an active lifestyle differ depending on the timing of physical activity in life or anthropometric characteristics. The aim of this study was to bring further insights to the association of physical activity in relation to menopausal status and body composition with breast cancer risk by making use of a prospective Swedish cohort (Malmö Diet and Cancer Study) with long-term follow-up. Physical activity information of 15,983 participants for the past 12 months prior to study entry was assessed according to metabolic equivalent task (MET)-hours/week to integrate duration and intensity of reported activities. During 23.2 years median follow-up, 1302 invasive breast cancers occurred. Women reporting a high physical activity at study baseline, corresponding to >1 h daily walking/week (≥28.5 MET-h/week), had a 23% lower long-term breast cancer risk (HRadj = 0.77, 95% CI 0.66−0.90) than those reporting low physical activity, being most pronounced among perimenopausal and postmenopausal women, and women with waist circumference, body fat percentage, or BMI in the upper-normal and overweight range. For premenopausal women or women having obesity or the largest body composition, high physical activity alone did not modify the breast cancer risk, suggesting additional preventive measures indicated in these groups to reduce the long-term risk of breast cancer.

Interaction of leisure-time physical activity with body mass index on the risk of obesity-related cancers: a pooled study

Physical activity (PA) has been associated with a lower risk of some obesity-related cancers, but the combined association and interaction of PA and body weight on obesity-related cancer risk is less clear. We examined the association of leisure-time PA (high/low) and its combination with body mass index (BMI, <25 [low]/≥25 [high] kg/m² ) on obesity-related cancer risk in 570 021 individuals, aged 43 years on average at baseline, in five Scandinavian cohorts. We used Cox regression to calculate hazard ratios of obesity-related cancers (n = 19 074) and assessed multiplicative and additive interactions between PA and BMI on risk. High leisure-time PA, recorded in 19% of the individuals, was associated with a 7% (95% confidence interval [CI] 4-10%) lower risk of any obesity-related cancer compared to low PA, with similar associations amongst individuals with a low and a high BMI (6% [1-11%] and 7% [2-11%]). High PA was also associated with decreased risks of renal cell (11% [9-31%]) and colon cancer (9% [2-16%]). When high PA and low BMI were combined, the relative risk reduction for all obesity-related cancers was 24% (95% CI 20-28%); endometrial cancer, 47% (35-57%); renal cell cancer, 39% (27-51%); colon cancer, 27% (19-35%); multiple myeloma, 23% (2-40%); and pancreatic cancer, 21% (4-35%), compared to low PA-high BMI. There were no additive or multiplicative interactions between PA and BMI on risk. The result of this study suggests a reduced risk of obesity-related cancer by leisure-time PA in both normal weight and overweight individuals, which further decreased for PA and normal weight combined.

Physical Activity and Attitudes Toward Exercise in People With Axial and Peripheral Spondyloarthritis

OBJECTIVE

To evaluate physical activity and attitudes toward exercise among people with axial (ax-) and peripheral (p-) spondyloarthritis (SpA).

METHODS

Using baseline information from an ongoing, longitudinal, prospective SpA cohort study (n = 264), self-reported attitudes and beliefs toward exercise were assessed using questionnaires. Total metabolic equivalent (MET) hours of self-reported physical activity per week, time spent in activities, and activity levels were calculated from the Nurses' Health Study Physical Activity Questionnaire II (NHSPAQ II). Adjusted multivariable linear models estimated the relationship between physical activity and disease status (axial vs peripheral).

RESULTS

Regardless of predominant anatomic distribution of disease, most participants were well-educated, non-Hispanic White men. Approximately 40% met the US Department of Health and Human Services physical activity recommendations. Positive attitudes, beliefs, and perceived benefits toward exercise were similar by anatomic distribution of disease. Despite similar MET h/week, participants with axial disease had greater concerns regarding discomfort and joint injuries than those with peripheral disease. Compared to those with pSpA (n = 201), participants with axSpA (n = 63) spent less time engaging in light and moderate activities (adjusted β in light activity: -1.94 min/week, 95% CI -2.96 to -0.93; adjusted β in moderate activity: -1.05 min/week, 95% CI -2.12 to 0.02).

CONCLUSION

Participants with axSpA had greater concerns regarding discomfort and injuries from exercise than those with pSpA. Although no differences in time spent in vigorous activities were observed, participants with axSpA spent less time than those with pSpA in light to moderate activities.

Actigraphy as an assessment of performance status in patients with advanced lung cancer

OBJECTIVE

Wearable devices such as a wrist actigraph may have a potential to objectively estimate patients' functioning and may supplement performance status (PS). This proof-of-concept study aimed to evaluate whether actigraphy data are significantly associated with patients' functioning and are predictive of their survival in patients with metastatic non-small cell lung cancer.

METHOD

We collected actigraphy data for a three-day period in ambulatory patients with stage IV non-small cell lung cancer. We computed correlations between actigraphy data (specifically, proportion of time spent immobile while awake) and clinician-rated PS, subjective report of physical activities, quality of life (the Functional Assessment of Cancer Therapy - Trial Outcome Index), and survival.

RESULT

Actigraphy data (the proportion of time awake spent immobile) were significantly correlated with Functional Assessment of Cancer Therapy - Trial Outcome Index (r = -0.53, p < 0.001) and with the Eastern Cooperative Oncology Group PS (ECOG PS) (r = 0.37, p < 0.001). The proportion of time awake spent immobile was significantly associated with worse survival. For each 10% increase in this measure, the hazard ratio (HR) was 1.48 (95% confidence interval [CI95%] = 1.06, 2.06) for overall mortality, and odds ratio was 2.99 (CI95% = 1.27, 7.05) for six-month mortality. ECOG PS was also associated with worse survival (HR = 2.80, CI95% = 1.34, 5.86). Among patients with ECOG PS 0-1, the percentage of time awake spent immobile was significantly associated with worse survival, HR = 1.93 (CI95% = 1.10, 3.42), whereas ECOG PS did not predict survival.

SIGNIFICANCE OF RESULTS

Actigraphy may have potential to predict important clinical outcomes, such as quality of life and survival, and may serve to supplement PS. Further validation study is warranted.

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.

Long-term yogurt consumption and risk of incident hypertension in adults

OBJECTIVE

To evaluate the relation between yogurt consumption as well as cheese, milk, and total dairy, and high blood pressure (HBP) in two Nurses' Health Study cohorts (NHS, n = 69 298), NHS II (n = 84 368) and the Health Professionals Follow-Up Study (HPFS, n = 30 512).

METHODS

NHS, NHS II, and HPFS participants were followed for incident HBP for up to 30, 20, and 24 years, respectively. Hazard ratios were calculated using time-dependent multivariate-adjusted Cox proportional hazards models. Pooled risk estimates were derived from fixed effects meta-analyses.

RESULTS

Participants consuming at least five servings per week (vs. <1 serving per month) of yogurt in NHS, NHS II, and HPFS had 19% (95% CI 0.75-0.87), 17% (95% CI 0.77-0.90), and 6% (95% CI 0.83-1.07) lower HBP risks, respectively. In pooled analyses of these cohorts, higher yogurt consumption was linked with 16% (95% CI 0.80-0.88) lower HBP risk; higher total dairy (3 to <6 vs. <0.5 servings/day), milk (2 to <6/day vs. <4/week) and cheese (1 to 4/day vs. <1/week) were associated with 16% (95% CI 0.81-0.87), 12% (95% CI 0.86-0.90), and 6% (95% CI 0.90-0.97) lower HBP risks, respectively. After controlling for BMI as a possible causal intermediate, total dairy, yogurt, milk, and cheese were associated with 13, 10, 8, and 8% lower HBP risks, respectively. The combination of higher yogurt intake and higher DASH ('Dietary Approaches to Stop Hypertension') diet scores was associated with 30% (95% CI 0.66-0.75) lower HBP risk compared with lower levels of both factors.

CONCLUSION

Higher total dairy intake, especially in the form of yogurt, was associated with lower risk of incident HBP in middle-aged and older adult men and women.

Physical Activity and Risk of Breast Cancer: A Meta-Analysis of 38 Cohort Studies in 45 Study Reports

OBJECTIVES

To evaluate and quantify the association between physical activity (PA) and risk of breast cancer.

METHODS

A systematic review meta-analysis was conducted. The literature was independently and manually searched by 2 reviewers through 3 English databases (PubMed, Embase, and ISI Web of Science) for data till October 2017. The quality of included studies was assessed by the Newcastle-Ottawa Quality Assessment Scale. Fixed-effects models were used to estimate the pooled relative risk and 95% confidence intervals (95% CI). Dose-response analysis was chosen for quantifying the association between PA and risk of breast cancer. The Begg test and the Egger test were used to estimate potential publication bias. Heterogeneity between studies was evaluated with I² statistics.

RESULTS

The meta-analysis included 38 cohort studies published between 1994 and 2017, which included 68 416 breast cancer cases. The overall relative risk (ORR) for breast cancer was 0.87 (95% CI 0.84-0.90). The inverse association was consistent among all subgroup analyses. In subgroup analysis by menopausal status, the ORR of breast cancer was 0.83 (95% CI 0.79-0.87) for premenopausal status and 0.91 (95% CI 0.85-0.97) for postmenopausal status. In subgroup analysis by PA type, the ORR for total activity was 0.87 (95% CI 0.81-0.93), for recreational activity 0.88 (95% CI 0.85-0.91), for occupational activity 0.91 (95% CI 0.84-0.99), and for nonoccupational activity 0.87 (95% CI 0.83-0.92). The risk of breast cancer was significantly lower in people with exposure periods longer than 1 year and less than 5 years (ORR 0.62; 95% CI 0.46-0.78), followed by those with lifetime activity (ORR 0.81; 95% CI 0.69-0.93). The ORR for subjects with body mass index of less than 25 kg/m² (0.88; 95% CI 0.83-0.93) was close to that for subjects with body mass index of more than 25 kg/m² (0.87; 95% CI 0.77-0.97). A linear relationship was found between breast cancer risk and PA (recreational activity and total activity), and the ORR was reduced by 3% (95% CI 0.95-0.99) for every 10 metabolic equivalent of energy hours per week increment in recreational PA and by 2% (95% CI 0.97-0.99) for every 10 metabolic equivalent of energy hours per week increment in total PA.

CONCLUSIONS

PA is significantly associated with a decrease in the risk of breast cancer.

Interplay between exercise and BMI; results from an equal access, racially diverse biopsy study

PURPOSE

It is unclear if exercise and BMI interact to influence prostate cancer (PC) risk. We hypothesized BMI is linked with increased aggressive PC risk but this link will be attenuated with increased exercise.

METHODS

Men undergoing prostate biopsy completed a questionnaire and metabolic equivalent (MET) hours of exercise was calculated. Of 695 men, 349 had PC; 161 low-grade, and 188 high-grade. We assessed the link between exercise and PC risk, high-grade PC (Gleason 7-10), and low-grade PC (Gleason 2-6) using logistic and multinomial logistic regression. Analysis was stratified by BMI. Link between BMI and PC risk and aggressive PC was similarly tested.

RESULTS

On multivariable analysis, there was no link between exercise and PC diagnosis in the entire cohort (p trend = 0.18-0.71) or across BMI groups (p trend = 0.15-0.97). For the entire cohort, higher BMI was linked with increased risk of high-grade PC (OR 1.06, p = 0.008). When stratified by exercise groups, the trend for higher BMI and increased risk of high-grade PC remained (OR 1.03-1.15, p = 0.02-0.66). There were no interactions between exercise and BMI in predicting PC risk (all p ≥ 0.31).

CONCLUSIONS

Regardless of exercise, higher BMI was linked with higher risk of aggressive PC, while exercise was unrelated to PC risk. Confirmatory studies are needed.

Applying pre-participation exercise screening to breast cancer survivors: a cross-sectional study

PURPOSE

Clinical guidelines recommend that breast cancer (BrCa) survivors be prescribed exercise. However, clinicians often do not prescribe exercise citing the presence of multiple health issues found among cancer survivors. No study has examined the proportion of BrCa survivors that can be prescribed a community/home-based unsupervised exercise program safely and independently, without further medical investigations or supervision.

METHODS

Participants included BrCa survivors who received treatment at a university healthcare system between 2009 and 2014. We applied previously identified published guidelines for health conditions that may impede BrCa survivors from completing a community/home-based exercise program. Logistic regression models were used to quantify the magnitude of the association between demographic and clinical characteristics and the ability to perform community/home-based exercise.

RESULTS

Among 667 BrCa survivors, 65 to 75% was classified as able to complete community/home-based exercise as recommended by the clinical guidelines. Older age, black race, treatment with chemotherapy, and treatment with radiation were associated with the potential need for further medical evaluation prior to starting exercise.

CONCLUSIONS

A large proportion of BrCa survivors can be prescribed community/home-based exercise program safely and independently, without further medical investigations or supervision. Future research will be needed to determine how to identify the subset of BrCa survivors that may benefit from medical evaluation prior to starting exercise in a manner that does not interrupt clinical oncology workflow. Approximately 35% of BrCa survivors may benefit from medical evaluation prior to starting community/home-based exercise.

Breast cancer risk prediction: an update to the Rosner-Colditz breast cancer incidence model

PURPOSE

To update and expand the Rosner-Colditz breast cancer incidence model by evaluating the contributions of more recently identified risk factors as well as predicted percent mammographic density (MD) to breast cancer risk.

METHODS

Using data from the Nurses' Health Study (NHS) and NHSII, we added adolescent somatotype (9 unit scale), vegetable intake (servings/day), breastfeeding (months), physical activity (MET-h/week), and predicted percent MD to the Rosner-Colditz model to determine whether these variables improved model discrimination. We evaluated all invasive as well as ER+/PR+, ER+/PR-, and ER-/PR- breast cancer.

RESULTS

In the NHS/NHSII, we accrued over 5200 cases of invasive breast cancer over more than 20 years of follow-up with complete data on the risk factors. Adolescent somatotype and predicted percent MD significantly improved the original Rosner-Colditz model for all invasive breast cancer (change in age-adjusted AUC = 0.020, p < 0.001). The relative risk (RR) of invasive breast cancer for a 4-unit increase in adolescent somatotype was 0.62 (95% CI 0.56, 0.70), whereas the RR for a 20-unit increase in predicted percent MD was 1.32 (95% CI 1.28, 1.36). Adolescent somatotype and predicted percent MD also significantly improved the ER+/PR+model (change in age-adjusted AUC = 0.020, p < 0.001) as well as the ER+/PR- model (change in age-adjusted AUC = 0.012, p = 0.007). Adolescent somatotype, predicted percent MD, breastfeeding, and vegetable intake improved the ER-/PR- model (change in AUC = 0.031, p < 0.0001). The RR of ER-/PR- disease for 5 vegetable servings/day increase was 0.83 (95% CI 0.70, 0.99), while the RR for every 12 months of breastfeeding was 0.88 (95% CI 0.77, 1.01). Physical activity did not improve risk classification in any model.

CONCLUSION

Adolescent somatotype and predicted percent MD significantly improved breast cancer risk classification using the Rosner-Colditz model. Further, risk factors specific to ER- disease, such as breastfeeding and vegetable intake, may also help improve risk prediction of this aggressive subtype.

Hair Coloring, Stress, and Smoking Increase the Risk of Breast Cancer: A Case-Control Study

PURPOSE

Epidemiologic characteristics of breast cancer in Iran are significantly different from those in the West and even other regional countries, but little is known about the related factors.

PATIENTS AND METHODS

A hospital-based case-control study was conducted on 1052 women (526 new cases and 526 controls). Logistic regression was performed to investigate associations of study factors with breast cancer risk.

RESULTS

This study introduced occupation (odds ratio [OR]_{employed/household}, 1.77; 95% confidence interval [CI], 1.15-2.69), marital age (OR_{24-30 y/< 18 y}, 2.13; 95% CI, 1.03-4.40), age at first delivery (OR_{≥ 30 y/< 18 y}, 3.53; 95% CI, 1.73-7.18), parity (OR_{1-2/Nulliparous or never married}, 2.61; 95% CI, 1.13-6.02), birth interval (OR_{30-50 mos/< 18 mos}, 2.38; 95% CI, 1.45-3.89), lifetime breastfeeding (OR_{≥ 42 mos/< 6 mos}, 0.37; 95% CI, 0.18-0.77), and menarche age (year) (OR, 0.87; 95% CI, 0.79-0.96) as significant associates of breast cancer. In addition, body mass index (OR, 1.07; 95% CI, 1.02-1.11) and some health-related behaviors including hair coloring on a regular basis (OR_yes/no, 1.93; 95% CI, 1.41-2.62), smoking (OR_yes/no, 2.02; 95% CI, 1.22-3.34), oral contraceptive usage (OR_ever/never. 1.46; 95% CI, 1.05-2.04), physical inactivity (OR_{inactive/regular activity}, 1.54; 95% CI, 1.39-1.75), past life stress (OR_{often stressful/often calm}, 2.40; 95% CI, 1.62-3.56), and regular bedtime (OR_{often regular/no}, 0.32; 95% CI, 0.19-0.54) were related to a higher risk of breast cancer.

CONCLUSION

This study revealed a significant number of factors that seem to contribute to the risk of breast cancer even more than the other previously introduced factors.

Exposure to Greenness and Mortality in a Nationwide Prospective Cohort Study of Women

BACKGROUND

Green, natural environments may ameliorate adverse environmental exposures (e.g., air pollution, noise, and extreme heat), increase physical activity and social engagement, and lower stress.

OBJECTIVES

We aimed to examine the prospective association between residential greenness and mortality.

METHODS

Using data from the U.S.-based Nurses' Health Study prospective cohort, we defined cumulative average time-varying seasonal greenness surrounding each participant's address using satellite imagery [Normalized Difference Vegetation Index (NDVI)]. We followed 108,630 women and observed 8,604 deaths between 2000 and 2008.

RESULTS

In models adjusted for mortality risk factors (age, race/ethnicity, smoking, and individual- and area-level socioeconomic status), women living in the highest quintile of cumulative average greenness (accounting for changes in residence during follow-up) in the 250-m area around their home had a 12% lower rate of all-cause nonaccidental mortality [95% confidence interval (CI); 0.82, 0.94] than those in the lowest quintile. The results were consistent for the 1,250-m area, although the relationship was slightly attenuated. These associations were strongest for respiratory and cancer mortality. The findings from a mediation analysis suggested that the association between greenness and mortality may be at least partly mediated by physical activity, particulate matter < 2.5 μm, social engagement, and depression.

CONCLUSIONS

Higher levels of green vegetation were associated with decreased mortality. Policies to increase vegetation may provide opportunities for physical activity, reduce harmful exposures, increase social engagement, and improve mental health. Planting vegetation may mitigate the effects of climate change; in addition, evidence of an association between vegetation and lower mortality rates suggests it also might be used to improve health.

CITATION

James P, Hart JE, Banay RF, Laden F. 2016. Exposure to greenness and mortality in a nationwide prospective cohort study of women. Environ Health Perspect 124:1344-1352; http://dx.doi.org/10.1289/ehp.1510363.

A prospective cohort study of endometriosis and subsequent risk of infertility

STUDY QUESTION

Is there a temporal relationship between endometriosis and infertility?

SUMMARY ANSWER

Endometriosis is associated with a higher risk of subsequent infertility, but only among women age <35 years.

WHAT IS KNOWN ALREADY

Endometriosis is the most commonly observed gynecologic pathology among infertile women undergoing laparoscopic examination. Whether endometriosis is a cause of infertility or an incidental discovery during the infertility examination is unknown.

STUDY DESIGN, SIZE, DURATION

This study included data collected from 58 427 married premenopausal female nurses <40 years of age from 1989 to 2005, who are participants of the Nurses' Health Study II prospective cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Our exposure was laparoscopically confirmed endometriosis. Multivariate Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for infertility risk (defined as attempting to conceive for >12 months) among women with and without endometriosis.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified 4612 incident cases of infertility due to any cause over 362 219 person-years of follow-up. Compared with women without a history of endometriosis, women with endometriosis had an age-adjusted 2-fold increased risk of incident infertility (HR = 2.12, 95% CI = 1.76-2.56) that attenuated slightly after accounting for parity. The relationship with endometriosis was only observed among women <35 years of age (multivariate HR <35 years = 1.77, 95% CI = 1.46-2.14; multivariate HR 35-39 years = 1.20, 95% CI = 0.94-1.53; P-interaction = 0.008). Risk of primary versus secondary infertility was similar subsequent to endometriosis diagnosis. Among women with primary infertility, 50% became parous after the endometriosis diagnosis, and among all women with endometriosis, 83% were parous by age 40 years.

LIMITATIONS, REASONS FOR CAUTION

We did not have information on participants' intentions to conceive, but by restricting the analytic population to married women we increased the likelihood that pregnancies were planned (and therefore infertility would be recognized). Women in our cohort with undiagnosed asymptomatic endometriosis will be misclassified as unexposed. However, the small proportion of these women are diluted among the >50 000 women accurately classified as endometriosis-free, minimizing the impact of exposure misclassification on the effect estimates.

WIDER IMPLICATIONS OF THE FINDINGS

This study supports a temporal association between endometriosis and infertility risk. Our prospective analysis indicates a possible detection bias in previous studies, with our findings suggesting that the infertility risk posed by endometriosis is about half the estimates observed in cross-sectional analyses.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the National Institutes of Health (grant numbers: UM1 CA176726, HD52473, HD57210, T32DK007703, T32HD060454, K01DK103720). We have no competing interests to declare.

Leisure time physical activity and cancer risk: evaluation of the WHO's recommendation based on 126 high-quality epidemiological studies

BACKGROUND

The WHO has concluded that physical activity reduces the risk of numerous diseases. However, few systemic reviews have been performed to assess the role of leisure time physical activity (LTPA) in lowering the risk of cancer in a dose-dependent manner and furthermore the suitability of recommendation of physical activity by the WHO.

METHODS

A systematic review and meta-analysis was designed to estimate cancer risk by LTPA in binary comparison and in a dose-dependent manner. MEDLINE and Web of Science were searched up to 30 December 2014 without language restrictions. Reference lists were reviewed for potential articles.

RESULTS

A total of 126 studies were recruited into the meta-analysis. Overall, the total cancer risk was reduced by 10% in people who undertook the most LTPA as compared with those who did the least. Dose-response meta-analysis indicated that the current WHO recommendation (equal to an average of 10 metabolic equivalents of energy hours per week) induced a 7% (95% CI 5% to 9%) cancer reduction. Moreover, the protective role of LTPA against cancer becomes saturated at 20 metabolic equivalents of energy hours per week, with a relative risk of 0.91 (95% CI 0.88 to 0.93). Subanalyses results based on cancer types showed that LTPA only exhibited significant protection against breast cancer and colorectal cancer.

CONCLUSIONS

Our meta-analysis indicates that the current WHO recommendation of physical activity can result in a 7% reduction in cancer risk, which is mainly attributed to its protective role against breast cancer and colorectal cancer. Furthermore, two-fold of current recommendation level is considered to give its saturated protection against cancer.

Classification of accelerometer wear and non-wear events in seconds for monitoring free-living physical activity

OBJECTIVE

To classify wear and non-wear time of accelerometer data for accurately quantifying physical activity in public health or population level research.

DESIGN

A bi-moving-window-based approach was used to combine acceleration and skin temperature data to identify wear and non-wear time events in triaxial accelerometer data that monitor physical activity.

SETTING

Local residents in Swansea, Wales, UK.

PARTICIPANTS

50 participants aged under 16 years (n=23) and over 17 years (n=27) were recruited in two phases: phase 1: design of the wear/non-wear algorithm (n=20) and phase 2: validation of the algorithm (n=30).

METHODS

Participants wore a triaxial accelerometer (GeneActiv) against the skin surface on the wrist (adults) or ankle (children). Participants kept a diary to record the timings of wear and non-wear and were asked to ensure that events of wear/non-wear last for a minimum of 15 min.

RESULTS

The overall sensitivity of the proposed method was 0.94 (95% CI 0.90 to 0.98) and specificity 0.91 (95% CI 0.88 to 0.94). It performed equally well for children compared with adults, and females compared with males. Using surface skin temperature data in combination with acceleration data significantly improved the classification of wear/non-wear time when compared with methods that used acceleration data only (p<0.01).

CONCLUSIONS

Using either accelerometer seismic information or temperature information alone is prone to considerable error. Combining both sources of data can give accurate estimates of non-wear periods thus giving better classification of sedentary behaviour. This method can be used in population studies of physical activity in free-living environments.

Dietary insulin index and insulin load in relation to endometrial cancer risk in the Nurses' Health Study

BACKGROUND

Although unopposed estrogen exposure is considered the main driver of endometrial carcinogenesis, factors associated with states of insulin resistance and hyperinsulinemia are independently associated with endometrial cancer risk. We used dietary insulin load and insulin index scores to represent the estimated insulin demand of overall diets and assessed their association with endometrial cancer risk in the prospective Nurses' Health Study.

METHODS

We estimated incidence rate ratios (RR) and 95% confidence intervals (CI) for risk of invasive endometrial cancer using Cox proportional hazards models. Between the baseline dietary questionnaire (1980) and 2010, we identified a total of 798 incident-invasive epithelial endometrial adenocarcinomas over 1,417,167 person-years of follow-up.

RESULTS

Dietary insulin scores were not associated with overall risk of endometrial cancer. Comparing women in the highest with the lowest quintile, the multivariable-adjusted RRs of endometrial cancer were 1.07 (95% CI, 0.84-1.35) for cumulative average dietary insulin load and 1.03 (95% CI, 0.82-1.31) for cumulative average dietary insulin index. Findings did not vary substantially by alcohol consumption, total dietary fiber intake, or body mass index and/or physical activity (P(heterogeneity) ≥ 0.10).

CONCLUSIONS

Intake of a diet predicted to stimulate a high postprandial insulin response was not associated with endometrial cancer risk in this large prospective study. Considering the complex interplay of diet, lifestyle, and genetic factors contributing to the hyperinsulinemic state, dietary measures alone may not sufficiently capture absolute long-term insulin exposure.

IMPACT

This study is the first to investigate dietary insulin scores in relation to endometrial cancer risk.

Physical activity and risk of endometrial adenocarcinoma in the Nurses' Health Study

Studies suggest that greater physical activity may reduce endometrial cancer risk. However, the role of the timing, duration and intensity of activity is unclear. We therefore examined recent and past recreational activities in relation to incident endometrial adenocarcinoma, and compared the importance of total and moderate- or vigorous-intensity activities as well as walking. We analyzed data from 71,570 women in the Nurses' Health Study, a prospective cohort that assessed activity in 1986, with updates every 2-4 years. Cox proportional hazards models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). During follow-up from 1986 to 2008 (1.2 million person-years), 777 invasive endometrial adenocarcinoma cases were documented. In multivariable models, compared with <3 MET-hr/week (<1 hr/week walking), women engaged in moderate (9 to <18 MET-hr/week: RR = 0.61, 95% CI: 0.48-0.78) or high (≥27 MET-hr/week: RR = 0.73, 95% CI: 0.58-0.92) amounts of recent total recreational activity were at reduced risk (p-trend = 0.001). Past total activity was not associated with risk. Greater recent moderate- or vigorous-intensity activity was associated with reduced risk (≥4 vs. 0 hr/week: RR = 0.65, 95% CI: 0.47-0.88, p-trend = 0.002). Among women who did not perform any vigorous activity, recent walking was associated with reduced risk (≥3 vs. <0.5 hr/week: RR = 0.65, 95% CI: 0.45-0.93, p-trend = 0.01), and faster walking pace was independently associated with risk reduction. After additional adjustment for body mass index, all associations were statistically non-significant. Greater recent physical activity, including activity of moderate duration and intensity such as walking, may reduce endometrial adenocarcinoma risk. This relation is largely mediated or confounded by body mass index.

Comparison of dietary and lifestyle habits among stage III and metastatic colorectal cancer patients: findings from CALGB 89803 and CALGB 80405

Self-administered questionnaires were completed by patients undergoing chemotherapy for stage III colon cancer (n=1095) and metastatic colorectal cancer (n=875). We describe the prevalence of a wide-range of health-related dietary patterns and lifestyle behaviors among colorectal cancer patients with stage III and metastatic disease and report notable similarities in these 2 cohorts.

BACKGROUND

Cancer patients often pursue lifestyle and dietary changes with the aim to improve outcomes. Using data from 2 large National Cancer Institute-sponsored clinical trials, we report on the dietary and lifestyle practices of patients receiving therapy for stage III colon or metastatic colorectal cancer.

PATIENTS AND METHODS

Self-administered questionnaires were completed by patients undergoing chemotherapy for stage III colon cancer (n=1095) and metastatic colorectal cancer (n=875). Descriptive statistical analyses were performed to evaluate anthropometrics, diet, and lifestyle in each cohort.

RESULTS

Median body mass index was comparable for stage III and metastatic patients (27.3 vs. 26.5 kg/m2). Stage III patients reported a modestly higher median level of physical activity than metastatic patients (4.6 vs. 3.4 metabolic equivalent task-hours per week). Ten percent of stage III and 9% of metastatic patients reported ongoing cigarette use. Avoidance of alcohol was reported by 47% of stage III and 43% of metastatic patients. Dietary patterns for both groups were comparable with more than 80% of stage III and metastatic patients failing to meet the recommended daily intake of vegetables, fruits, and milk products. Usage of at least 2 multivitamins per week was reported by 49% of stage III and 40% of metastatic patients. Two percent of stage III and 5% of metastatic patients reported vitamin D supplement use.

CONCLUSIONS

We observed notable similarities in dietary and lifestyle behaviors between stage III colon and metastatic colorectal cancer patients actively receiving chemotherapy. Future research should aim to elucidate the effect of these behaviors on patient outcomes.

Physical activity and risk of breast cancer: a meta-analysis of prospective studies

We conducted a meta-analysis to summarize the evidence from prospective studies regarding the association between physical activity and breast cancer risk. A comprehensive search was conducted to identify eligible studies. The fixed or random effect model was used based on heterogeneity test. The dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. Overall, 31 studies with 63,786 cases were included, and the combined relative risk (RR) with 95 % CI of breast cancer was 0.88 (0.85-0.91). In subgroup analysis by activity type, data from 27 studies including 37,568 cases for non-occupational activity (including recreational activity and household activity) and seven studies including 28,268 cases for occupational activity were used, and the RR (95 % CI) of breast cancer was 0.87 (0.83-0.91) and 0.90 (0.83-0.97), respectively. The inverse association was consistent among all subgroups analyses. Stronger association was found for subjects with BMI <25 kg/m(2) [0.72 (0.65-0.81)], premenopausal women [0.77 (0.72-0.84)], and estrogen and progesterone receptor-negative breast cancer [0.80 (0.73-0.87)]. Dose-response analysis suggested that the risk of breast cancer decreased by 2 % (P < 0.00) for every 25 metabolic equivalent (MET)-h/week increment in non-occupational physical activity, 3 % (P < 0.00) for every 10 MET-h/week (roughly equivalent to 4 h/week of walking in 2 miles/h or 1 h/week of running in 6 miles/h) increment in recreational activity, and 5 % (P < 0.00) for every 2 h/week increment in moderate plus vigorous recreational activity, respectively. Physical activity could significantly reduce the risk of breast cancer.

Risk factors for breast cancer for women aged 40 to 49 years: a systematic review and meta-analysis

BACKGROUND

Identifying risk factors for breast cancer specific to women in their 40s could inform screening decisions.

PURPOSE

To determine what factors increase risk for breast cancer in women aged 40 to 49 years and the magnitude of risk for each factor.

DATA SOURCES

MEDLINE (January 1996 to the second week of November 2011), Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (fourth quarter of 2011), Scopus, reference lists of published studies, and the Breast Cancer Surveillance Consortium.

STUDY SELECTION

English-language studies and systematic reviews of risk factors for breast cancer in women aged 40 to 49 years. Additional inclusion criteria were applied for each risk factor.

DATA EXTRACTION

Data on participants, study design, analysis, follow-up, and outcomes were abstracted. Study quality was rated by using established criteria, and only studies rated as good or fair were included. Results were summarized by using meta-analysis when sufficient studies were available or from the best evidence based on study quality, size, and applicability when meta-analysis was not possible. Data from the Breast Cancer Surveillance Consortium were analyzed with proportional hazards models by using partly conditional Cox regression. Reference groups for comparisons were set at U.S. population means.

DATA SYNTHESIS

Sixty-six studies provided data for estimates. Extremely dense breasts on mammography or first-degree relatives with breast cancer were associated with at least a 2-fold increase in risk for breast cancer. Prior breast biopsy, second-degree relatives with breast cancer, or heterogeneously dense breasts were associated with a 1.5- to 2.0-fold increased risk; current use of oral contraceptives, nulliparity, and age 30 years or older at first birth were associated with a 1.0- to 1.5-fold increased risk.

LIMITATIONS

Studies varied by measures, reference groups, and adjustment for confounders, which could bias combined estimates. Effects of multiple risk factors were not considered.

CONCLUSION

Extremely dense breasts and first-degree relatives with breast cancer were each associated with at least a 2-fold increase in risk for breast cancer in women aged 40 to 49 years. Identification of these risk factors may be useful for personalized mammography screening.

PRIMARY FUNDING SOURCE

National Cancer Institute.

Risk factors for breast cancer for women aged 40 to 49 years: a systematic review and meta-analysis

BACKGROUND

Identifying risk factors for breast cancer specific to women in their 40s could inform screening decisions.

PURPOSE

To determine what factors increase risk for breast cancer in women aged 40 to 49 years and the magnitude of risk for each factor.

DATA SOURCES

MEDLINE (January 1996 to the second week of November 2011), Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (fourth quarter of 2011), Scopus, reference lists of published studies, and the Breast Cancer Surveillance Consortium.

STUDY SELECTION

English-language studies and systematic reviews of risk factors for breast cancer in women aged 40 to 49 years. Additional inclusion criteria were applied for each risk factor.

DATA EXTRACTION

Data on participants, study design, analysis, follow-up, and outcomes were abstracted. Study quality was rated by using established criteria, and only studies rated as good or fair were included. Results were summarized by using meta-analysis when sufficient studies were available or from the best evidence based on study quality, size, and applicability when meta-analysis was not possible. Data from the Breast Cancer Surveillance Consortium were analyzed with proportional hazards models by using partly conditional Cox regression. Reference groups for comparisons were set at U.S. population means.

DATA SYNTHESIS

Sixty-six studies provided data for estimates. Extremely dense breasts on mammography or first-degree relatives with breast cancer were associated with at least a 2-fold increase in risk for breast cancer. Prior breast biopsy, second-degree relatives with breast cancer, or heterogeneously dense breasts were associated with a 1.5- to 2.0-fold increased risk; current use of oral contraceptives, nulliparity, and age 30 years or older at first birth were associated with a 1.0- to 1.5-fold increased risk.

LIMITATIONS

Studies varied by measures, reference groups, and adjustment for confounders, which could bias combined estimates. Effects of multiple risk factors were not considered.

CONCLUSION

Extremely dense breasts and first-degree relatives with breast cancer were each associated with at least a 2-fold increase in risk for breast cancer in women aged 40 to 49 years. Identification of these risk factors may be useful for personalized mammography screening.

PRIMARY FUNDING SOURCE

National Cancer Institute.

A meta-analysis of fat intake, reproduction, and breast cancer risk: an evolutionary perspective

OBJECTIVES

This study is a systematic review of literature published up to May of 2010 aimed to identify relationships between dietary fat, and fat subtypes, with risk of breast cancer in women.

METHODS

Descriptive data, estimates of relative risk and associated 95% confidence interval (CI) were extracted from relative studies and analyzed using the random effects model of DerSimonian and Laird.

RESULTS

Cohort study results indicated significant summary relative risks between polyunsaturated fat and breast cancer (1.091, 95% CI: 1.001; 1.184). In case-control studies no association between fat and breast cancer was observed. Post-menopausal women indicated a significant association between total fat (1.042, 95%CI: 1.013; 1.073), PUFA intake (1.22, 95% CI: 1.08; 1.381), and breast cancer. A non-significant inverse relation between intake of all fat types and breast cancer was identified in premenopausal women.

CONCLUSIONS

These results support the idea that possible elevations in serum estrogen levels by an adult exposure to a high-fat diet would increase breast cancer risk. Furthermore, menopausal status was observed to affect women's risk of breast cancer. Higher risks of breast cancer were found in post-menopausal women consuming diets high in total fat and polyunsaturated fats. Conversely, dietary fat appears to have preventative effects in pre-menopausal women. This study takes a transformative approach combining epidemiological, biomedical, and evolutionary theory to evaluate how biocultural variations in risk factors (i.e., diet and reproduction) affect the evolution of breast cancers.

Validation of accelerometer wear and nonwear time classification algorithm

INTRODUCTION

the use of movement monitors (accelerometers) for measuring physical activity (PA) in intervention and population-based studies is becoming a standard methodology for the objective measurement of sedentary and active behaviors and for the validation of subjective PA self-reports. A vital step in PA measurement is the classification of daily time into accelerometer wear and nonwear intervals using its recordings (counts) and an accelerometer-specific algorithm.

PURPOSE

the purpose of this study was to validate and improve a commonly used algorithm for classifying accelerometer wear and nonwear time intervals using objective movement data obtained in the whole-room indirect calorimeter.

METHODS

we conducted a validation study of a wear or nonwear automatic algorithm using data obtained from 49 adults and 76 youth wearing accelerometers during a strictly monitored 24-h stay in a room calorimeter. The accelerometer wear and nonwear time classified by the algorithm was compared with actual wearing time. Potential improvements to the algorithm were examined using the minimum classification error as an optimization target.

RESULTS

the recommended elements in the new algorithm are as follows: 1) zero-count threshold during a nonwear time interval, 2) 90-min time window for consecutive zero or nonzero counts, and 3) allowance of 2-min interval of nonzero counts with the upstream or downstream 30-min consecutive zero-count window for detection of artifactual movements. Compared with the true wearing status, improvements to the algorithm decreased nonwear time misclassification during the waking and the 24-h periods (all P values < 0.001).

CONCLUSIONS

the accelerometer wear or nonwear time algorithm improvements may lead to more accurate estimation of time spent in sedentary and active behaviors.

Physical activity reduces breast cancer risk: a case-control study in Tunisia

PURPOSE

This study examined the relationship between lifetime history of physical activity and breast cancer risk.

METHODS

The case-control study was conducted on 400 women with histological confirmed breast cancer operated during the 2006-2009 period at Farhat Hached University Hospital, Sousse, Tunisia, and 400 cancer-free controls, aged 25-75 years. The physical activity was assessed using a structured questionnaire on each activity: type, duration, frequency, and intensity. Odds ratios (ORs), 95% confidence intervals (CI) and a full confounding assessment, included in this analysis, were derived using logistic regression.

RESULTS

These cases had lower lifetime averages for total physical activity for both forms of activity measurements (hours/week/year and MET-hours/week/year) and (P(trend)<0.001 and P(trend)=0.002, respectively). Significant risk reductions were found in total physical activity for both forms of activity measurements (OR=0.27, 95% CI: 0.18-0.52, OR=0.42, 95% CI: 0.26-0.73, respectively) for the highest versus the lowest level of activity (P(trend)=0.001 and 0.004, respectively). The stratification by menopausal status showed a significant 56% reduction in breast cancer risk for post-menopausal women (P(trend)=0.001, adjusted for age). The risk was further reduced to 68% (P(trend)=0.002, multivariate adjusted). Among pre-menopausal women, the total physical activity was not significantly associated with reduced risk, ORs were 0.88 (95% CI: 0.40-1.99, age adjusted) and 0.43 (95% CI: 0.12-1.38, multivariate adjusted).

CONCLUSION

These data are in concordance with the majority of previous reports which involved physical inactivity as an important risk factor for breast cancer.

Physical activity and breast cancer prevention

Breast cancer is the most commonly diagnosed invasive malignancy and the second leading cause of cancer death in women. This chapter considers epidemiologic evidence regarding the association between physical activity and breast cancer risk from 73 studies conducted around the world. Across these studies there was a 25% average risk reduction amongst physically active women as compared to the least active women. The associations were strongest for recreational activity, for activity sustained over the lifetime or done after menopause, and for activity that is of moderate to vigorous intensity and performed regularly. There is also some evidence for a stronger effect of physical activity amongst postmenopausal women, women who are normal weight, have no family history of breast cancer, and are parous. It is likely that physical activity is associated with decreased breast cancer risk via multiple interrelated biologic pathways that may involve adiposity, sex hormones, insulin resistance, adipokines, and chronic inflammation. Future research should include prospective observational epidemiologic studies relating proposed biomarkers to breast cancer risk and also randomized controlled trials to examine how physical activity influences the proposed biomarkers. Exercise trials will provide more clarity regarding the appropriate type, dose, and timing of activity that relate to breast cancer risk reduction.

Estrogen and progesterone exposure is reduced in response to energy deficiency in women aged 25-40 years

BACKGROUND

Alterations in circulating steroids are believed to be important mediators of the impact that diet and exercise have on breast cancer risk and changes in bone density. This study aimed to test the hypothesis that moderate exercise training combined with caloric restriction would produce significant menstrual disturbances and alterations in ovarian steroids in premenopausal women.

METHODS

Sedentary premenopausal women (25-40 years; body mass index: 23.6 +/- 0.6 kg/m(2)) assigned to either a light conditioning (LC, n = 9) or an exercise combined with caloric restriction group (EX + CR, n = 24) were studied for one screening, one baseline and four intervention periods equivalent to the length of subjects' menstrual cycles. Exercise consisted of supervised training sessions, i.e. two LC or four EX + CR times per week, 30-60 min at a moderate intensity. The EX + CR group was prescribed a diet representing a caloric restriction of 20-35% below baseline energy requirements, whereas the LC group remained eucaloric. Ovarian steroid exposure was determined with daily urinary estrone-1- and pregnanediol glucuronides (E1G and PdG, respectively) and mid-cycle urinary LH measures. Fitness, body composition, and serum sex hormone binding globulin (SHBG) and serum estradiol (E2) were assessed repeatedly.

RESULTS

The intervention produced significant increases in VO(2) max and decreases in both body weight (-3.7 +/- 0.5 kg; ranged from -8.8 to +1.8 kg) and percent body fat (-4.5 +/- 0.7%; ranged from -12 to +0.3%), which were attributable primarily to changes in the EX + CR subjects (time x group; P < 0.05). Serum E2 and urinary E1G and PdG concentrations declined significantly across the intervention period (time; P < 0.05), whereas SHBG increased transiently (time; P < 0.05) in the EX + CR subjects, with no significant changes observed in the LC group. The decrease in E1G area under the curve was significantly related to the daily energy deficit (R =0.61; P = 0.003), not the amount of weight lost. There was no significant impact of the intervention on menstrual cyclicity or the incidence of menstrual disturbances in either group.

CONCLUSIONS

A moderate aerobic exercise training program combined with modest weight loss in accordance with recommended guidelines produces significant reductions in ovarian steroid exposure without disrupting menstrual cyclicity in premenopausal women aged 25-40 years. Exposure to a daily energy deficit is a stronger predictor of the decline in estrogen exposure than decreases in body weight.

A systematic review of the evidence for Canada's Physical Activity Guidelines for Adults

This systematic review examines critically the scientific basis for Canada's Physical Activity Guide for Healthy Active Living for adults. Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases (cardiovascular disease, stroke, hypertension, colon cancer, breast cancer, type 2 diabetes (diabetes mellitus) and osteoporosis). The strength of the relationship between physical activity and specific health outcomes is evaluated critically. Literature was obtained through searching electronic databases (e.g., MEDLINE, EMBASE), cross-referencing, and through the authors' knowledge of the area. For inclusion in our systematic review articles must have at least 3 levels of physical activity and the concomitant risk for each chronic disease. The quality of included studies was appraised using a modified Downs and Black tool. Through this search we identified a total of 254 articles that met the eligibility criteria related to premature all-cause mortality (N = 70), cardiovascular disease (N = 49), stroke (N = 25), hypertension (N = 12), colon cancer (N = 33), breast cancer (N = 43), type 2 diabetes (N = 20), and osteoporosis (N = 2). Overall, the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified. Moreover, higher levels of physical activity reduce the risk for premature all-cause mortality. The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality.

Physical activity and the risk of community-acquired pneumonia in US women

BACKGROUND

Exercise bolsters the immune system and can prevent various infections in certain populations. However, limited data exist regarding the role of physical activity and the risk of community-acquired pneumonia.

METHODS

During a 12-year period, we prospectively examined the association between physical activity and the risk of community-acquired pneumonia among 83,165 women in the Nurses' Health Study II who were between the ages of 27 and 44 years in 1991. We excluded women who had pneumonia before 1991 and those with a history of cancer, cardiovascular disease, or asthma. Biennial self-administered mailed questionnaires were used to determine activity level. Cases of pneumonia required a diagnosis by a physician and confirmation with a chest radiograph.

RESULTS

We identified 1265 new cases of community-acquired pneumonia during 965,168 person-years of follow up. After adjusting for age, women in the highest quintile of physical activity were less likely to develop pneumonia than women in the lowest quintile (relative risk [RR] = 0.72; 95% confidence interval [CI], 0.60-0.86; P for trend<.001). However, the association was attenuated and only marginally significant after further adjusting for body mass index, smoking, and alcohol use (RR=0.84; 95% CI, 0.70-1.01; P for trend=.06). Women in the highest quintile of walking were less likely to develop pneumonia compared with women who walked the least (multivariate adjusted RR=0.82; 95% CI, 0.69-0.98); however, the trend across quintiles was not significant (P for trend=.25).

CONCLUSION

Higher physical activity does not substantially reduce pneumonia risk in well-nourished women.

Adult physical activity and endometriosis risk

BACKGROUND

Regular exercise has been associated with a 40%-80% reduction in risk for endometriosis in several case-control studies. However, women experiencing symptoms prior to their diagnosis may be less likely to exercise than healthy controls, thus biasing the observed association.

METHODS

Using data collected from the Nurses' Health Study II, a prospective cohort study of premenopausal US nurses that began in 1989, we have attempted to clarify this relation. Data are updated every 2 years with follow-up for these analyses through 2001. In 1989, 1991, and 1997 women reported average amount of time per week engaging in various physical activities. A metabolic equivalent (MET) score was assigned to each activity, and these were summed to estimate total activity.

RESULTS

A total of 102,197 premenopausal women contributed 996,422 person-years of follow-up with 2703 cases of laparoscopically confirmed endometriosis. After adjusting for BMI at age 18, current BMI, smoking, parity, infertility status, oral contraceptive use, age at menarche, and menstrual cycle length and pattern in college, we observed only a slight reduction in the incidence of endometriosis, comparing the highest level of activity (>or=42 MET hours/week) to the lowest (<3 MET hours/week) (rate ratio = 0.89 [95% confidence interval = 0.77-1.03]). The association was limited to participants with no past or concurrent infertility (P = 0.002, test for heterogeneity). No associations were seen with inactivity.

CONCLUSIONS

In this first prospective assessment, we did not find evidence of the strong inverse association previously reported, although we cannot rule out a modest inverse association.

Physical activity and premenopausal breast cancer: an examination of recall and selection bias

BACKGROUND

Compared with cohort studies, case-control investigations have tended to report clearer protective associations for the relationship between physical activity and premenopausal breast cancer risk.

METHODS

We conducted a case-control study within the Nurses' Health Study II cohort to examine whether recall or selection bias could explain the stronger protective associations. Self-reported total recreational physical activity during adulthood and over a woman's lifetime (ages 12 years to current) were assessed in 1997 before diagnosis and, again, from one to seven years after breast cancer diagnosis among the same women.

RESULTS

Eighty-seven percent of cases (417 of 479) and 82% of controls (390 of 474) responded. Selection bias was observed for activity during adulthood but not for activity over a woman's lifetime. Recall bias was not observed in the direction we expected: the odds ratios (ORs) for breast cancer comparing the highest versus lowest quintile of prospectively reported total activity were not significantly different than the corresponding estimates from retrospective reports (e.g., lifetime activity: prospective OR = 0.58, 95% CI: 0.37, 0.93 versus retrospective OR = 0.80; 95% CI: 0.50, 1.29).

CONCLUSION

Recall or selection bias may not have been accounted for protective associations among case-control investigations examining lifetime recreational physical activity and breast cancer. Selection bias related to recreational physical activity during adulthood and random error in the measurement of physical activity remain concerns.

Prospective study of physical activity and risk of postmenopausal breast cancer

INTRODUCTION

To prospectively examine the relation of total, vigorous and non-vigorous physical activity to postmenopausal breast cancer risk.

METHODS

We studied 32,269 women enrolled in the Breast Cancer Detection Demonstration Project Follow-up Study. Usual physical activity (including household, occupational and leisure activities) throughout the previous year was assessed at baseline using a self-administered questionnaire. Postmenopausal breast cancer cases were identified through self-reports, death certificates and linkage to state cancer registries. A Cox proportional hazards regression was used to estimate the relative risk and 95% confidence intervals of postmenopausal breast cancer associated with physical activity.

RESULTS

During 269,792 person-years of follow-up from 1987 to 1998, 1506 new incident cases of postmenopausal breast cancer were ascertained. After adjusting for potential risk factors of breast cancer, a weak inverse association between total physical activity and postmenopausal breast cancer was suggested (relative risk comparing extreme quintiles = 0.87; 95% confidence interval = 0.74 to 1.02; p for trend = 0.21). That relation was almost entirely contributed by vigorous activity (relative risk comparing extreme categories = 0.87; 95% confidence interval = 0.74 to 1.02; p for trend = 0.08). The inverse association with vigorous activity was limited to women who were lean (ie, body mass index <25.0 kg/m2: relative risk = 0.68; 95% confidence interval = 0.54 to 0.85). In contrast, no association with vigorous activity was noted among women who were overweight or obese (ie, body mass index > or = 25.0 kg/m2: relative risk = 1.18; 95% confidence interval = 0.93 to 1.49; p for interaction = 0.008). Non-vigorous activity showed no relation to breast cancer (relative risk comparing extreme quintiles = 1.02; 95% confidence interval = 0.87 to 1.19; p for trend = 0.86). The physical activity and breast cancer relation was not specific to a certain hormone receptor subtype.

CONCLUSIONS

In this cohort of postmenopausal women, breast cancer risk reduction appeared to be limited to vigorous forms of activity; it was apparent among normal weight women but not overweight women, and the relation did not vary by hormone receptor status. Our findings suggest that physical activity acts through underlying biological mechanisms that are independent of body weight control.

Physical activity and breast cancer risk among pre- and postmenopausal women in the U.S. Radiologic Technologists cohort

To clarify aspects of the association between physical activity and breast cancer, such as activity intensity required, and possible effect modification by factors such as menopausal hormone therapy (MHT) use. We prospectively examined physical activity in relation to breast cancer risk among 45,631 women participating in the U.S. Radiologic Technologists cohort. Participants provided information at baseline regarding hours spent per week engaging in strenuous activity, walking/hiking for exercise, and walking at home or work. We estimated multivariable relative risks (RR) and 95% confidence intervals (CI) of breast cancer using Cox regression. We identified 864 incident-invasive breast cancers. Greatest risk reduction was observed among women who reported walking/hiking for exercise 10 or more hours per week (RR, 0.57; 95% CI, 0.34-0.95) compared with those reporting no walking/hiking. The association between walking/hiking for exercise and breast cancer was modified by MHT use (p for interaction = 0.039). Postmenopausal women who never used MHT had reduced risks of breast cancer associated with physical activity whereas no relation was observed among ever users of MHT. Our study suggests moderate intensity physical activity, such as walking, may protect against breast cancer. Further, the relation between physical activity and breast cancer may be modified by MHT use.

A prospective study of age-specific physical activity and premenopausal breast cancer

BACKGROUND

Physical activity has been consistently associated with lower risk of postmenopausal breast cancer, but its relationship with premenopausal breast cancer is unclear. We investigated whether physical activity is associated with reduced incidence of premenopausal breast cancer, and, if so, what age period and intensity of activity are critical.

METHODS

A total of 64,777 premenopausal women in the Nurses' Health Study II reported, starting on the 1997 questionnaire, their leisure-time physical activity from age 12 to current age. Cox regression models were used to examine the relationship between physical activity, categorized by age period (adolescence, adulthood, and lifetime) and intensity (strenuous, moderate, walking, and total), and risk of invasive premenopausal breast cancer.

RESULTS

During 6 years of follow-up, 550 premenopausal women developed breast cancer. The strongest associations were for total leisure-time activity during participants' lifetimes rather than for any one intensity or age period. Active women engaging in 39 or more metabolic equivalent hours per week (MET-h/wk) of total activity on average during their lifetime had a 23% lower risk of premenopausal breast cancer (relative risk = 0.77; 95% confidence interval = 0.64 to 0.93) than women reporting less activity. This level of total activity is equivalent to 3.25 h/wk of running or 13 h/wk of walking. The age-adjusted incidence rates of breast cancer for the highest (> or = 54 MET-h/wk) and lowest (< 21 MET-h/wk) total lifetime physical activity categories were 136 and 194 per 100 000 person-years, respectively. High levels of physical activity during ages 12-22 years contributed most strongly to the association.

CONCLUSIONS

Leisure-time physical activity was associated with a reduced risk for premenopausal breast cancer in this cohort. Premenopausal women regularly engaging in high amounts of physical activity during both adolescence and adulthood may derive the most benefit.

Joint effects of body size, energy intake, and physical activity on breast cancer risk

To evaluate the joint effect of body size, energy intake, and physical activity on breast cancer risk, we analyzed information on body weight history, energy intake, anthropometric measurements, and physical activity patterns in a population based case-control study. Included in this analysis were 3,458 incidence breast cancer cases and 3,474 age-frequency matched controls from the Shanghai Breast Cancer Study. High weight, height, body mass index, waist-to-hip ratio, and weight gain showed stronger associations with breast cancer risk in postmenopausal women than premenopausal women. High total physical activity was inversely associated with postmenopausal breast cancer risk (p for trend=0.026) and premenopausal breast cancer (p for trend=0.059). The odds ratios for women with a high waist-to-hip ratio (>or=0.84) and low total physical activity (<or=10.9 MET-h/day) had the highest risk for breast cancer (OR=2.7, 95% CI: 1.4-4.9 for postmenopausal women, OR=2.1, 95% CI: 1.5-3.1 for premenopausal women) compared to their counterpart with low waist-to-hip ratio (<0.76) and high total physical activity (>20.5 MET-h/day). We did not find a statistically significant multiplicative interaction between body size, caloric intake and total physical activity on breast cancer risk.

Measures of energy balance and mammographic density in the Nurses' Health Study

Mammographic density is a strong risk factor for breast cancer; however the mechanism that underlies this association is unclear. We hypothesized that measures of energy balance early in life and in adulthood may be associated with mammographic density. We conducted a cross-sectional analysis of 1,398 women in the Nurses' Health Study to examine associations between physical activity, childhood and current body fatness, weight gain from age 18 years to present and mammographic density. Percent mammographic density was measured from digitized mammograms by a computer-assisted method. Demographic and lifestyle data were obtained from prospectively collected questionnaires. For all analyses, subjects were stratified into three groups: premenopausal women, postmenopausal women not currently taking hormones, and postmenopausal women currently taking hormones. Childhood body fatness was inversely associated with mammographic density. The correlations ranged from -0.15 to -0.19 in the three strata of women (P<or=0.001). The difference in mean percent mammographic density between the leanest and heaviest body types ranged from 6.2 to 9.9%. Similarly, adult body fatness was inversely associated with percent mammographic density. The correlations ranged from -0.41 to -0.48 in the three strata of women (P<0.0001). The difference in mean percent mammographic density between the leanest and heaviest body types ranged from 22.3 to 35.1%. Weight gain from age 18 was also inversely associated with mammographic density. There was no association between recent physical activity and mammographic density. These findings indicate that childhood and adult body fatness and weight change from age 18 are inversely associated with mammographic density.