A nested case-control study of the association between melatonin secretion and incident myocardial infarction

OBJECTIVES

Low nocturnal melatonin secretion is associated with cardiovascular risk factors, diabetes and hypertension, while individuals with prevalent cardiovascular disease have lower nocturnal melatonin levels. However, the prospective association of melatonin secretion with myocardial infarction (MI) has not been studied. We aimed to study the association between melatonin secretion and the risk of developing MI.

METHODS

We performed a prospective nested case-control study of participants from the Nurses' Health Study cohorts I and II. A total of 209 incident cases of fatal and non-fatal MI were identified among women who provided first morning voided urine specimens at baseline and were matched to 209 controls. Nocturnal melatonin secretion was assessed using 6-sulfatoxymelatonin concentrations in morning urines normalised to the urines' creatinine concentration. Multivariable conditional logistic regression was used to analyse associations independent of important risk factors.

RESULTS

Lower melatonin secretion was significantly associated with a higher risk of MI. After conditioning on matching variables, the OR for every one unit lower log-transformed sulfatoxymelatonin/creatinine ratio was 1.51 (95% CI 1.16 to 1.96). In multivariable models controlling for factors included in the American Heart Association Cardiovascular Risk Score plus circadian factors, every one unit lower in the ratio was associated with a significantly increased risk of MI (OR, 1.40; 95% CI 1.02 to 1.93). Women in the highest category had an estimated absolute risk of MI of 84 cases per 100 000 person-years compared with 197 cases per 100 000 person-years in the lowest category. The association was strongly modified by body mass index (BMI) (p value for interaction=0.02).

CONCLUSIONS

Lower melatonin secretion was significantly associated with a greater risk of incident MI in women with increased BMI. Melatonin may be a novel and modifiable risk factor for MI among such women.

Associations among rotating night shift work, sleep and skin cancer in Nurses' Health Study II participants

BACKGROUND

Night shift work and sleep duration have been associated with breast and other cancers. Results from the few prior studies of night shift work and skin cancer risk have been mixed and not fully accounted for other potentially important health-related variables (eg, sleep characteristics). This study evaluated the relationship between rotating night shift work and skin cancer risk and included additional skin cancer risk factors and sleep-related variables.

METHODS

The current study used data from 74 323 Nurses' Health Study (NHS) II participants. Cox proportional hazards models were used to estimate multivariable-adjusted HRs and 95% CIs for skin cancers across categories of shift work and sleep duration.

RESULTS

Over 10 years of follow-up, 4308 basal cell carcinoma (BCC), 334 squamous cell carcinoma (SCC) and 212 melanoma cases were identified. Longer duration of rotating night shifts was associated with a linear decline in risk of BCC (HR=0.93, 95% CI 0.90 to 0.97 per 5-year increase). Shift work was not significantly associated with either melanoma (HR=1.02, 95% CI 0.86 to 1.21) or SCC (HR=0.92, 95% CI 0.80 to 1.06). A short sleep duration (≤6 hours per day) was associated with lower risks of melanoma (HR=0.68, 95% CI 0.46 to 0.98) and BCC (HR=0.93, 95% CI 0.86 to 1.00) compared with the most common report of 7 hours. SCC was not associated with duration of sleep (HR=0.94, 95% CI 0.83 to 1.06).

CONCLUSIONS

Longer duration of rotating night shift work and shorter sleep duration were associated with lower risk of some skin cancers. Further research is needed to confirm and identify the mechanisms underlying these associations.

Association of urinary melatonin levels and aging-related outcomes in older men

BACKGROUND

Circadian disruptions can contribute to accelerated aging, and the circadian system regulates cognitive and physical functions; therefore, circadian markers (eg, melatonin) may be associated with key aspects of healthy aging and longevity.

OBJECTIVE

To evaluate urinary melatonin levels in relation to cognitive function, physical function, and mortality among 2,821 older men in the Osteoporotic Fractures in Men Study DESIGN: Cohort study.

MEASUREMENTS

In 2003-2005, participants provided first-morning spot urine samples, which were assayed for 6-sulfatoxymelatonin (the primary melatonin metabolite in urine); cognitive and physical function assessments were completed twice, at baseline and an average of 6.5 years later. Participant deaths were confirmed by central review of death certificates over a mean of 9.2 years of follow up.

RESULTS

In multivariable-adjusted regression models, we observed a significant trend of better Digit Vigilance Test scores (ie, decreased time to completion) at baseline across increasing melatonin quartiles (p-trend = 0.01); however, mean time-to-completion scores did not significantly differ comparing extreme quartiles (group means: 547.1 seconds (95% CI: 533.6, 560.6) versus 561.3 seconds (95% CI: 547.8, 574.9)), and there were no associations of urinary melatonin levels with other cognitive test scores, or any cognitive change scores over time. Furthermore, melatonin levels were not related to physical function scores (p-trends = 0.4 for walking speed, 0.7 for chair stands, and 0.6 for grip strength in fully-adjusted models) or mortality risk (p-trend = 0.3 in the fully-adjusted model).

CONCLUSION

We found little evidence of associations between urinary melatonin levels and key measures of healthy aging and mortality in this cohort of older men. Further research should explore the relation of melatonin, particularly if assessed earlier in life, and other circadian markers with healthy aging outcomes.

Association Between Rotating Night Shift Work and Risk of Coronary Heart Disease Among Women

IMPORTANCE

Prospective studies linking shift work to coronary heart disease (CHD) have been inconsistent and limited by short follow-up.

OBJECTIVE

To determine whether rotating night shift work is associated with CHD risk.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study of 189,158 initially healthy women followed up over 24 years in the Nurses' Health Studies (NHS [1988-2012]: N = 73,623 and NHS2 [1989-2013]: N = 115,535).

EXPOSURES

Lifetime history of rotating night shift work (≥3 night shifts per month in addition to day and evening shifts) at baseline (updated every 2 to 4 years in the NHS2).

MAIN OUTCOMES AND MEASURES

Incident CHD; ie, nonfatal myocardial infarction, CHD death, angiogram-confirmed angina pectoris, coronary artery bypass graft surgery, stents, and angioplasty.

RESULTS

During follow-up, 7303 incident CHD cases occurred in the NHS (mean age at baseline, 54.5 years) and 3519 in the NHS2 (mean age, 34.8 years). In multivariable-adjusted Cox proportional hazards models, increasing years of baseline rotating night shift work was associated with significantly higher CHD risk in both cohorts. In the NHS, the association between duration of shift work and CHD was stronger in the first half of follow-up than in the second half (P=.02 for interaction), suggesting waning risk after cessation of shift work. Longer time since quitting shift work was associated with decreased CHD risk among ever shift workers in the NHS2 (P<.001 for trend). [table: see text]

CONCLUSIONS AND RELEVANCE

Among women who worked as registered nurses, longer duration of rotating night shift work was associated with a statistically significant but small absolute increase in CHD risk. Further research is needed to explore whether the association is related to specific work hours and individual characteristics.

Sleep Duration in Relation to Cognitive Function among Older Adults: A Systematic Review of Observational Studies

CONTEXT

Increasing evidence suggests that circadian and sleep parameters influence cognitive function with aging.

OBJECTIVE

To evaluate observational studies of sleep duration and cognition in older adults.

DATA SOURCES

A systematic review of OVID Medline and PsycINFO through September 2015, and review of bibliographies from studies identified.

STUDY SELECTION

English-language articles reporting observational studies of sleep duration and cognitive function in older populations.

DATA EXTRACTION

Data extraction by 2 authors using predefined categories of desired information.

RESULTS

Thirty-two studies met our inclusion criteria, with nearly two-thirds published in the past 4 years. One-third of studies indicated that extreme sleep durations were associated with worse cognition in older adults. More studies favored an association with long vs. short sleep durations (35 vs. 26% of studies, respectively). Four studies found that greater changes in sleep duration over time were related to lower cognition. Study design and analytic methods were very heterogeneous across studies; therefore, meta-analysis was not undertaken.

LIMITATIONS

We reviewed English-language manuscripts only, with a qualitative summary of studies identified.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Observational studies of sleep duration and cognitive function in older adults have produced mixed results, with more studies suggesting that long (rather than short) sleep durations are related to worse cognition. Studies more consistently indicate that greater changes in sleep duration are associated with poor cognition. Future studies should be prospectively designed, with objective sleep assessment and longer follow-up periods; intervention studies are also needed to identify strategies for promoting cognitive health with aging.

Mismatch of Sleep and Work Timing and Risk of Type 2 Diabetes

OBJECTIVE

To examine whether a mismatch between chronotype (i.e., preferred sleep timing) and work schedule is associated with type 2 diabetes risk.

RESEARCH DESIGN AND METHODS

In the Nurses' Health Study 2, we followed 64,615 women from 2005 to 2011. Newly developed type 2 diabetes was the outcome measure (n = 1,452). A question on diurnal preference ascertained chronotype in 2009; rotating night shift work exposure was assessed regularly since 1989.

RESULTS

Compared with intermediate chronotypes, early chronotypes had a slightly decreased diabetes risk after multivariable adjustment (odds ratio 0.87 [95% CI 0.77-0.98]), whereas no significant association was observed for late chronotypes (1.04 [0.89-1.21]). Among early chronotypes, risk of type 2 diabetes was modestly reduced when working daytime schedules (0.81 [0.63-1.04]) and remained similarly reduced in women working <10 years of rotating night shifts (0.84 [0.72-0.98]). After ≥10 years of shift work exposure, early chronotypes had a nonsignificant elevated diabetes risk (1.15 [0.81-1.63], Ptrend = 0.014). By contrast, among late chronotypes, the significantly increased diabetes risk observed among day workers (1.51 [1.13-2.02]) appeared largely attenuated if their work schedules included night shifts (<10 years: 0.93 [0.76-1.13]; ≥10 years: 0.87 [0.56-1.34]; Ptrend = 0.14). The interaction between chronotype and shift work exposure was significant (Pinteraction = 0.0004). Analyses restricting to incident cases revealed similar patterns.

CONCLUSIONS

In early chronotypes, type 2 diabetes risk increased with increasing duration of shift work exposure, whereas late types had the highest diabetes risk working daytime schedules. These data add to the growing body of evidence that workers could benefit from shift schedules minimizing interference with chronotype-dependent sleep timing.

Association of Urinary 6-Sulfatoxymelatonin (aMT6s) Levels and Objective and Subjective Sleep Measures in Older Men: The MrOS Sleep Study

BACKGROUND

Sleep and melatonin have been associated with healthy aging. In this study, we examine the association between melatonin levels and sleep among older men.

METHODS

Cross-sectional study of a community-dwelling cohort of 2,821 men aged 65 years or older recruited from six U.S. centers. First morning void urine samples were collected to measure melatonin's major urinary metabolite, 6-sulfatoxymelatonin (aMT6s). We also assessed objective and subjective sleep parameters. We used logistic regression models to calculate multivariate (MV) odds ratios (ORs), and 95% confidence intervals (CIs) adjusted for important demographic variables and comorbidities.

RESULTS

In the overall sample, the only significant finding in fully adjusted models was that aMT6s levels were inversely associated with subjectively measured daytime sleepiness (sleepiness mean score of 5.79 in the top aMT6s quartile, and 6.26 in the bottom aMT6s quartile, MV OR, 1.32; 95% CI, 0.95-1.84; p trend ≤ .02). When restricting to men without β-blocker use (a known melatonin suppressant), aMT6s levels were significantly associated with shorter sleep time, that is, less than 5 hours (MV OR, = 1.90; 95% CI, 1.21-2.99; p trend = .01), and worse sleep efficiency, that is, less than 70% (MV OR, 1.58; 95% CI, 1.28-2.65; p trend < .001). aMT6s were not associated with subjective sleep quality or respiratory disturbance in any of our analyses.

CONCLUSION

Lower nocturnal melatonin levels were associated with worsened daytime sleepiness, sleep efficiency, and shorter sleep time in older men. The role of circadian interventions, and whether melatonin levels are a modifiable risk factor for poor sleep in older men, warrants further study.

Work schedule and physical factors in relation to fecundity in nurses

OBJECTIVES

To evaluate the association of work schedule and physical factors with fecundity.

METHODS

Women currently employed outside the home and trying to get pregnant (n=1739) in the Nurses' Health Study 3 cohort (2010-2014) were included in this analysis. Work schedule and physical labour were self-reported on the baseline questionnaire, and every 6 months thereafter the women reported the duration of their ongoing pregnancy attempt. Multivariable accelerated failure time models were used to estimate time ratios (TR) and 95% CIs.

RESULTS

Among the 1739 women (median age=33 years, 93% Caucasian) the estimated proportions of women not pregnant after 12 and 24 months were 16% and 5%, respectively. None of the various shift work patterns were associated with duration of pregnancy attempt (as a surrogate for fecundity). However, women working >40 h/week had a 20% (95% CI 7 to 35%) longer median duration of pregnancy attempt compared to women working 21-40 h/week (p-trend=0.005). Women whose work entailed heavy lifting or moving (ie, 25+ pounds) >15 times/day also had a longer median duration of pregnancy attempt (adjusted TR=1.49; 95% CI 1.20 to 1.85) compared to women who never lifted or moved heavy loads (p-trend=0.002). The association between heavy moving and lifting and duration of pregnancy attempt was more pronounced among overweight or obese women (body mass index, BMI<25: TR=1.17; 95% CI 0.88 to 1.56; BMI≥25: TR=2.03, 95% CI 1.48 to 2.79; p-interaction=0.007).

CONCLUSIONS

Working greater than 40 h per week and greater frequency of lifting or moving a heavy load were associated with reduced fecundity in a cohort of nurses planning pregnancy.

Lifestyle, family history, and risk of idiopathic Parkinson disease: a large Danish case-control study

The relationship between Parkinson disease (PD) and smoking has been examined in several studies, but little is known about smoking in conjunction with other behaviors and a family history of PD. Using unconditional logistic regression analysis, we studied individual and joint associations of these factors with idiopathic PD among 1,808 Danish patients who were diagnosed in 1996-2009 and matched to 1,876 randomly selected population controls. Although there was a downward trend in duration of smoking, this was not observed for daily tobacco consumption. A moderate intake of caffeine (3.1-5 cups/day) was associated with a lower odds ratio for PD (0.45, 95% confidence interval: 0.34, 0.62), as was a moderate intake of alcohol (3.1-7 units/week) (odds ratio = 0.60, 95% confidence interval: 0.58, 0.84); a higher daily intake did not reduce the odds further. When these behaviors were studied in combination with smoking, the odds ratios were lower than those for each one alone. Compared with never smokers with no family history of PD, never smokers who did have a family history had an odds ratio of 2.81 (95% confidence interval: 1.91, 4.13); for smokers with a family history, the odds ratio was 1.60 (95% confidence interval: 1.15, 2.23). In conclusion, duration of smoking seems to be more important than intensity in the relationship between smoking and idiopathic PD. The finding of lower risk estimates for smoking in combination with caffeine or alcohol requires further confirmation.

Occupational history of night shift work and Parkinson's disease in Denmark

OBJECTIVES

We investigated whether working night shifts was associated with the risk of Parkinson's disease (PD).

METHODS

Between January 2008 and December 2010, we recruited 1808 patients with a confirmed diagnosis of idiopathic PD from Denmark and 1876 population controls matched by year of birth and gender. Information on lifelong occupational history, including information on night work, smoking, caffeine and alcohol consumption habits, and family history of PD was collected through structured telephone interviews.

RESULTS

Overall, there was no association between a history of night shift work and PD [odds ratio (OR) for any type of night work (ie, either permanent or rotating night work) 1.01, 95% confidence interval (95% CI) 0.86-1.21]. Compared with persons who never worked night shifts, risks of those with longer durations of night work did not appear to differ (OR <10 years=0.95, 95% CI 0.75-1.19, OR 10-19 years= 1.09, 95% CI 0.77-1.53, OR ≥20 years=1.05, 95% CI 0.81-1.37, P for trend=0.23). Associations were similar among men and women.

CONCLUSIONS

These data suggest that working night shifts is not associated with PD or that low tolerance for night shift work is an early marker of PD. Due to the novel and exploratory nature of these findings, confirmation is needed.

The association of body size in early to mid-life with adult urinary 6-sulfatoxymelatonin levels among night shift health care workers

Background

Adult body mass index (BMI) has been associated with urinary melatonin levels in humans; however, whether earlier-life body size is associated with melatonin, particularly among night shift workers, remains unknown.

Methods

We evaluated associations of birth weight, body shape (or somatotype) at ages 5 and 10, BMI at age 18 and adulthood, weight change since age 18, waist circumference, waist to hip ratio, and height with creatinine-adjusted morning urinary melatonin (6-sulfatoxymelatonin, aMT6s) levels among 1,343 healthy women (aged 32–53 at urine collection, 1996–1999) in the Nurses’ Health Study (NHS) II cohort. Using multivariable linear regression, we computed least-square mean aMT6s levels across categories of body size, and evaluated whether these associations were modified by night shift work.

Results

Adult BMI was inversely associated with aMT6s levels (mean aMT6s levels = 34 vs. 50 ng/mg creatinine, comparing adult BMI ≥30 vs. <20 kg/m²; P_trend <0.0001); however, other measures of body size were not related to aMT6s levels after accounting for adult BMI. Night shifts worked prior to urine collection, whether recent or cumulatively over time, did not modify the association between adult BMI and aMT6s levels (e.g., P_interaction = 0.72 for night shifts worked within two weeks of urine collection).

Conclusions

Our results suggest that adult BMI, but not earlier measures of body size, is associated with urinary aMT6s levels in adulthood. These observations did not vary by night shift work status, and suggest that adult BMI may be an important mechanism by which melatonin levels are altered and subsequently influence chronic disease risk.

Total and cause-specific mortality of U.S. nurses working rotating night shifts

BACKGROUND

Rotating night shift work imposes circadian strain and is linked to the risk of several chronic diseases.

PURPOSE

To examine associations between rotating night shift work and all-cause; cardiovascular disease (CVD); and cancer mortality in a prospective cohort study of 74,862 registered U.S. nurses from the Nurses' Health Study.

METHODS

Lifetime rotating night shift work (defined as ≥3 nights/month) information was collected in 1988. During 22 years (1988-2010) of follow-up, 14,181 deaths were documented, including 3,062 CVD and 5,413 cancer deaths. Cox proportional hazards models estimated multivariable-adjusted hazard ratios (HRs) and 95% CIs.

RESULTS

All-cause and CVD mortality were significantly increased among women with ≥5 years of rotating night shift work, compared to women who never worked night shifts. Specifically, for women with 6-14 and ≥15 years of rotating night shift work, the HRs were 1.11 (95% CI=1.06, 1.17) and 1.11 (95% CI=1.05, 1.18) for all-cause mortality and 1.19 (95% CI=1.07, 1.33) and 1.23 (95% CI=1.09, 1.38) for CVD mortality. There was no significant association between rotating night shift work and all-cancer mortality (HR≥15years=1.08, 95% CI=0.98, 1.19) or mortality of any individual cancer, with the exception of lung cancer (HR≥15years=1.25, 95% CI=1.04, 1.51).

CONCLUSIONS

Women working rotating night shifts for ≥5 years have a modest increase in all-cause and CVD mortality; those working ≥15 years of rotating night shift work have a modest increase in lung cancer mortality. These results add to prior evidence of a potentially detrimental effect of rotating night shift work on health and longevity.

Antihypertensive medication use and incident breast cancer in women

The purpose of this study was to evaluate whether antihypertensive medication use, including long-term use, is associated with increased breast cancer incidence in women. We studied 210,641 U.S. registered nurses participating in the Nurses' Health Study (NHS) and Nurses' Health Study II (NHS II). Information on antihypertensive medication use was collected on biennial questionnaires in both cohorts, and breast cancer cases were ascertained during this period. Multivariable-adjusted Cox proportional hazard models were used to estimate relative risks of invasive breast cancer over follow-up (1988-2012 in NHS, 1989-2011 in NHS II) across categories of overall antihypertensive medication use and use of specific classes (diuretics, beta blockers, calcium channel blockers, and angiotensin-converting enzyme inhibitors). During follow-up, 10,012 cases of invasive breast cancer developed (6718 cases in NHS and 3294 in the NHS II). Overall, current use of any antihypertensive medication was not associated with breast cancer risk compared with past/never use in NHS (multivariable-adjusted relative risk = 1.00, 95 % CI = 0.95-1.06) or NHS II (multivariable-adjusted relative risk = 0.94, 95 % CI = 0.86-1.03). Furthermore, no specific class of antihypertensive medication was consistently associated with breast cancer risk. Results were similar when we considered hypertensive women only, and when we evaluated consistency and duration of medication use over time. Overall, antihypertensive medication use was largely unrelated to the risk of invasive breast cancer among women in the NHS cohorts.

Urinary melatonin concentration and the risk of breast cancer in Nurses' Health Study II

Experimental and epidemiologic data support a protective role for melatonin in breast cancer etiology, yet studies in premenopausal women are scarce. In a case-control study nested within the Nurses' Health Study II cohort, we measured the concentration of melatonin's major urinary metabolite, 6-sulfatoxymelatonin (aMT6s), in urine samples collected between 1996 and 1999 among 600 breast cancer cases and 786 matched controls. Cases were predominantly premenopausal women who were diagnosed with incident breast cancer after urine collection and before June 1, 2007. Using multivariable conditional logistic regression, we computed odds ratios and 95% confidence intervals. Melatonin levels were not significantly associated with total breast cancer risk (for the fourth (top) quartile (Q4) of aMT6s vs. the first (bottom) quartile (Q1), odds ratio (OR) = 0.91, 95% confidence interval (CI): 0.64, 1.28; Ptrend = 0.38) or risk of invasive or in situ breast cancer. Findings did not vary by body mass index, smoking status, menopausal status, or time between urine collection and diagnosis (all Pinteraction values ≥ 0.12). For example, the odds ratio for total breast cancer among women with ≤5 years between urine collection and diagnosis was 0.74 (Q4 vs. Q1; 95% CI: 0.45, 1.20; Ptrend = 0.09), and it was 1.20 (Q4 vs. Q1; 95% CI: 0.72, 1.98; Ptrend = 0.70) for women with >5 years. Our data do not support an overall association between urinary melatonin levels and breast cancer risk.

Work schedule and physically demanding work in relation to menstrual function: the Nurses' Health Study 3

OBJECTIVES

This study aimed to evaluate occupational exposures and menstrual cycle characteristics among nurses.

METHODS

Using cross-sectional data collected in 2010-2012 from 6309 nurses aged 21-45 years, we investigated nurses' menstrual function in the Nurses' Health Study 3. We used multivariable regression modeling to analyze the associations between occupational exposures and prevalence of irregular cycles and long and short cycle lengths.

RESULTS

The cohort reported cycle length as <21 (1.5%), 21-25 (15.6%), 26-31 (69.7%), and 32-50 (13.2%) days. In addition, 19% of participants reported irregular cycles. Working ≥41 hours/week was associated with a 16% [95% confidence interval (95% CI): 4-29%] higher prevalence of irregular cycles and a higher prevalence of very short (<21-day) cycles [prevalence odds ratio (OR) 1.93, 95% CI 1.24-3.01] in adjusted models. Irregular menstrual cycles were more prevalent among women working nights only (32% higher; 95% CI 15-51%) or rotating nights (27% higher, 95% CI 10-47%), and was associated with the number of night shifts per month (P for trend <0.0001). Rotating night schedule was associated with long (32-50 day) cycles (OR 1.28, 95% CI 1.03-1.61). Heavy lifting was associated with a higher prevalence of irregular cycles (34% higher), and the prevalence of cycles <21 days and 21-25 day cycles increased with increasing heavy lifting at work (P for trend <0.02 for each endpoint).

CONCLUSION

Night work, long hours, and physically demanding work might relate to menstrual disturbances.

Alcohol, one-carbon nutrient intake, and risk of colorectal cancer according to tumor methylation level of IGF2 differentially methylated region

BACKGROUND

Although a higher consumption of alcohol, which is a methyl-group antagonist, was previously associated with colorectal cancer risk, mechanisms remain poorly understood.

OBJECTIVE

We hypothesized that excess alcohol consumption might increase risk of colorectal carcinoma with hypomethylation of insulin-like growth factor 2 (IGF2) differentially methylated region-0 (DMR0), which was previously associated with a worse prognosis.

DESIGN

With the use of a molecular pathologic epidemiology database in 2 prospective cohort studies, the Nurses' Health Study and Health Professionals Follow-up Study, we examined the association between alcohol intake and incident colorectal cancer according to the tumor methylation level of IGF2 DMR0. Duplication-method Cox proportional cause-specific hazards regression for competing risk data were used to compute HRs and 95% CIs. In addition, we investigated intakes of vitamin B-6, vitamin B-12, methionine, and folate as exposures.

RESULTS

During 3,206,985 person-years of follow-up, we identified 993 rectal and colon cancer cases with an available tumor DNA methylation status. Compared with no alcohol consumption, the consumption of ≥15 g alcohol/d was associated with elevated risk of colorectal cancer with lower levels of IGF2 DMR0 methylation [within the first and second quartiles: HRs of 1.55 (95% CI: 1.08, 2.24) and 2.11 (95% CI: 1.44, 3.07), respectively]. By contrast, alcohol consumption was not associated with cancer with higher levels of IGF2 DMR0 methylation. The association between alcohol and cancer risk differed significantly by IGF2 DMR0 methylation level (P-heterogeneity = 0.006). The association of vitamin B-6, vitamin B-12, and folate intakes with cancer risk did not significantly differ according to IGF2 DMR0 methylation level (P-heterogeneity > 0.2).

CONCLUSIONS

Higher alcohol consumption was associated with risk of colorectal cancer with IGF2 DMR0 hypomethylation but not risk of cancer with high-level IGF2 DMR0 methylation. The association between alcohol intake and colorectal cancer risk may differ by tumor epigenetic features.

Night shift work at specific age ranges and chronic disease risk factors

OBJECTIVES

We examined the association of night shift work history and age when night shift work was performed with cancer and cardiovascular disease risk factors among 54 724 women in the Nurses' Health Study (NHS) II.

METHODS

We calculated age-adjusted and socioeconomic status-adjusted means and percentages for cancer and cardiovascular risk factors in 2009 across categories of night shift work history. We used multivariable-adjusted logistic regression to estimate odds ratios (ORs) and 95% CIs for key risk factors among 54 724 participants (72% ever shift workers). We further examined these associations by age (20-25, 26-35, 36-45 and 46+ years) at which shift work was performed.

RESULTS

Ever night shift workers had increased odds of obesity (body mass index ≥30 kg/m(2); OR=1.37, 95% CI 1.31 to 1.43); higher caffeine intake (≥131 mg/day; OR=1.16, 95% CI 1.12 to 1.22) and total calorie intake (≥1715 kcal/day; OR=1.09, 95% CI 1.04 to 1.13); current smoking (OR=1.30, 95% CI 1.19 to 1.42); and shorter sleep durations (≤7 h of sleep/day; OR=1.19, 95% CI 1.15 to 1.24) compared to never night shift workers. These estimates varied depending on age at which night work was performed, with a suggestion that night shift work before age 25 was associated with fewer risk factors compared to night shift work at older ages.

CONCLUSIONS

Our results indicate that night shift work may contribute to an adverse chronic disease risk profile, and that risk factors may vary depending on the age at which night shift work was performed.

Circulating vitamin D, supplement use, and cardiovascular disease risk: the MrOS Sleep Study

CONTEXT

Evidence suggests an inverse association between circulating 25(OH) vitamin D and cardiovascular disease (CVD).

OBJECTIVE

To determine the association between serum 25(OH) vitamin D and risk for CVD events.

SETTING AND DESIGN

From March 2000 to April 2002, participants were recruited for the Osteoporotic Fractures in Men (MrOS) study. Between December 2003 and March 2005, members of the MrOS cohort were invited to participate in the MrOS Sleep Study. Participants were recruited from 6 clinical centers across the United States and followed for a mean of 5.9 years. Three-thousand-one-hundred-thirty-five men ages 65 and older were included from the MrOS cohort, of whom 116 were excluded for missing vitamin D or CVD data. Participants were divided into two groups based on serum 25(OH) vitamin D levels, <20 ng/mL and ≥20 ng/mL. Participants were followed for CVD endpoints including coronary heart disease (CHD) and cerebrovascular events. Age- and multivariable-adjusted hazard ratios were calculated and stratified by use of vitamin D containing supplements.

RESULTS

We observed no significant association between circulating 25(OH) vitamin D and risk of CVD event (HR, 0.91; 95% confidence interval (CI), 0.73-1.13) and CHD event (HR, 0.81; 95% CI, 0.61-1.07). For cerebrovascular events, men with vitamin D deficiency exhibited a higher risk (HR, 1.44; 95% CI, 1.00-2.08) using the minimally adjusted model and after excluding supplement users (HR, 1.70; 95% CI, 1.02-2.83).

CONCLUSIONS

25(OH) vitamin D was not associated with risk of CVD and CHD events. However, vitamin D deficiency may be associated with an increased risk of cerebrovascular events.

Urinary melatonin levels, sleep disruption, and risk of prostate cancer in elderly men

Melatonin has anticarcinogenic properties in experimental models. We undertook a case-cohort study of 928 Icelandic men without prostate cancer (PCa) nested within the Age, Gene/Environment Susceptibility (AGES)-Reykjavik cohort to investigate the prospective association between first morning-void urinary 6-sulfatoxymelatonin (aMT6s) levels and the subsequent risk for PCa, under the hypothesis that men with lower aMT6s levels have an increased risk for advanced PCa. We used weighted Cox proportional hazards models to assess the association between first morning-void aMT6s levels and PCa risk, adjusting for potential confounders. A total of 111 men were diagnosed with incident PCa, including 24 with advanced disease. Men who reported sleep problems at baseline had lower morning aMT6s levels compared with those who reported no sleep problems. Men with morning aMT6s levels below the median had a fourfold statistically significant increased risk for advanced disease compared with men with levels above the median (hazard ratio: 4.04; 95% confidence interval, 1.26-12.98). These results require replication in larger prospective studies with longer follow-up.

PATIENT SUMMARY

In this report, we evaluated the prospective association between urinary aMT6s levels and risk of PCa in an Icelandic population. We found that lower levels of aMT6s were associated with an increased risk for advanced PCa.

Sleep duration in midlife and later life in relation to cognition

OBJECTIVES

To evaluate associations between sleep duration at midlife and later life and change in sleep duration over time and cognition in older women.

DESIGN

Participants reported sleep duration in 1986 and 2000, and a subgroup of older participants began cognitive testing in 1995 to 2001; follow-up testing was conducted three times, at 2-year intervals.

SETTING

Prospective Nurses' Health Study cohort.

PARTICIPANTS

Female nurses aged 70 and older free of stroke and depression at the initial cognitive assessment (N = 15,385).

MEASUREMENTS

Validated, telephone-based cognitive battery to measure cognitive function; four repeated assessments over 6 years were averaged to estimate overall cognition at older ages, and trajectories of cognitive change were evaluated over follow up.

RESULTS

Extreme sleep durations in later life were associated with worse average cognition (P < .001 for the quadratic term for a global score averaging all six cognitive tests). For example, women sleeping 5 h/d or less had worse global cognition than those sleeping 7 h/d, as did women sleeping 9 h/d or more; differences were equivalent to nearly 2 additional years of age. Associations were similar, although slightly attenuated, for sleep duration in midlife. Women whose sleep duration changed by 2 h/d or more over time had worse cognition than women with no change in sleep duration (e.g., for the global score, P < .001 for the quadratic term). Sleep duration was not associated with trajectories of cognitive function over 6 years, which might be attributable to short follow-up for detecting cognitive decline.

CONCLUSION

Extreme sleep durations at midlife and later life and extreme changes in sleep duration over time appear to be associated with poor cognition in older women.

A randomized, placebo-controlled trial of melatonin on breast cancer survivors: impact on sleep, mood, and hot flashes

The purpose is to examine the effects of melatonin supplementation on sleep, mood, and hot flashes in postmenopausal breast cancer survivors. In a randomized, double-blind, placebo-controlled study, 95 postmenopausal women with a prior history of stage 0-III breast cancer, who had completed active cancer treatment (including hormonal therapy) were randomly assigned 1:1 to either 3 mg oral melatonin (n = 48) or placebo daily (n = 47) for 4 months. Sleep, mood, and hot flashes were assessed at baseline and 4 months via self-administered questionnaire using the Pittsburgh Sleep Quality Index (PSQI), Center for Epidemiologic Studies-Depression (CES-D), and the North Central Cancer Treatment Group (NCCTG) hot flash diary, respectively. Eighty-six women (91 %) completed the study and provided pre- and post-questionnaires. At baseline, 52 % of participants reported poor sleep in the month prior to enrollment. Compared to subjects on placebo, subjects randomized to melatonin experienced significantly greater improvements in subjective sleep quality as measured by the PSQI, including domains on sleep quality, daytime dysfunction and total score. For example, the mean change in PSQI score was -0.1 in the placebo group compared to -1.9 in the melatonin group (p < 0.001). There were no significant differences in measures of depression or hot flashes. Sleep disturbances are common among breast cancer survivors, even after completion of active cancer treatment. This is the first randomized placebo-controlled study among breast cancer survivors to demonstrate that melatonin was associated with an improvement in subjective sleep quality, without any significant adverse effects.

Rotating night-shift work and lung cancer risk among female nurses in the United States

The risk of lung cancer among night-shift workers is unknown. Over 20 years of follow-up (1988-2008), we documented 1,455 incident lung cancers among 78,612 women in the Nurses' Health Study. To examine the relationship between rotating night-shift work and lung cancer risk, we used multivariate Cox proportional hazard models adjusted for detailed smoking characteristics and other risk factors. We observed a 28% increased risk of lung cancer among women with 15 or more years spent working rotating night shifts (multivariate relative risk (RR) = 1.28, 95% confidence interval (CI): 1.07, 1.53; Ptrend = 0.03) compared with women who did not work any night shifts. This association was strongest for small-cell lung carcinomas (multivariate RR = 1.56, 95% CI: 0.99, 2.47; Ptrend = 0.03) and was not observed for adenocarcinomas of the lung (multivariate RR = 0.91, 95% CI: 0.67, 1.24; Ptrend = 0.40). Further, the increased risk associated with 15 or more years of rotating night-shift work was limited to current smokers (RR = 1.61, 95% CI: 1.21, 2.13; Ptrend < 0.001), with no association seen in nonsmokers (Pinteraction = 0.03). These results suggest that there are modestly increased risks of lung cancer associated with extended periods of night-shift work among smokers but not among nonsmokers. Though it is possible that this observation was residually confounded by smoking, our findings could also provide evidence of circadian disruption as a "second hit" in the etiology of smoking-related lung tumors.

Abstract B37: Urinary melatonin levels and risk of breast cancer in the Nurses' Health Study II

Shift work has been hypothesized to increase breast cancer risk as two recent meta-analyses suggest a 21- 51% increased risk of breast cancer in women reporting night shift work. Melatonin, a hormone produced by the pineal gland that follows a circadian rhythm with highest levels observed at night, is frequently referenced as the biological mechanism through which shift work may increase breast cancer risk. While decreased urinary melatonin levels are associated with an increased risk of breast cancer in postmenopausal women, only three studies have evaluated the association between melatonin levels and breast cancer in premenopausal women with inconsistent findings. Therefore, we investigated this relationship in predominantly premenopausal women by conducting a nested case-control study in the prospective Nurses' Health Study II cohort. From 1996 to 1999, first morning urine was collected from 29,613 cancer-free participants who were followed through June 2007. Incident breast cancer was confirmed through review of medical records and pathology reports, and potential confounders were reported on biennial questionnaires and a questionnaire administered at urine collection. Concentrations of 6-sulfatoxymelatonin (aMT6s), the major metabolite of melatonin, were available for 603 cases and 798 controls matched for age, menopausal status, ethnicity, fasting status, luteal day of menstrual cycle, and month, year, day, and time of urine collection. We used multivariable conditional logistic regression models to estimate the risk of breast cancer by quartile of urinary aMT6s concentrations, with cutpoints based on values of control participants. We did not observe an association between melatonin levels and risk of breast cancer (odds ratio for highest versus lowest aMT6s quartile: 0.87, 95% confidence interval: 0.57-1.35). Our results were largely unchanged when we examined the relationship between urinary melatonin levels and invasive breast cancer (n=443 cases, odds ratio for highest versus lowest aMT6s quartile: 0.91, 95% CI: 0.54-1.56), in situ breast cancer (n=160 cases, odds ratio for highest versus lowest aMT6s quartile: 1.23, 95% CI: 0.45-3.35), and among women with ER+ tumors (n=398 cases, odds ratio for highest versus lowest aMT6s quartile: 0.77, 95% CI: 0.44-1.34). These prospective data do not provide strong support for a significant association between urinary melatonin levels and breast cancer risk in predominantly premenopausal women.

Citation Format: Susan Boyer Brown, Susan E. Hankinson, Eva S. Schernhammer. Urinary melatonin levels and risk of breast cancer in the Nurses' Health Study II. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr B37.