Sleep Duration and Breast Cancer: A Prospective Cohort Study

Abstract

Breast cancer incidence has increased during recent decades for reasons that are only partly understood. Prevalence of sleeping difficulties and sleepiness has increased, whereas sleeping duration per night has decreased. We hypothesized that there is an inverse association between sleep duration and breast cancer risk, possibly due to greater overall melatonin production in longer sleepers. This populationbased study includes information from women born in Finland before 1958. Sleep duration, other sleep variables, and breast cancer risk factors were assessed by selfadministered questionnaires given in 1975 and in 1981. Breast cancer incidence data for 1976 to 1996 was obtained from the Finnish Cancer Registry. Hazard ratios (HR) and 95% confidence intervals (CI) were obtained from Cox proportional hazards models adjusting for potential confounders. Altogether, 242 cases of breast cancer occurred over the study period among the 12,222 women with sleep duration data in 1975. For these women, the HRs for breast cancer in the short (V6 hours), average (7-8 hours), and long sleep (z9 hours) duration groups were 0.85 (CI, 0.54-1.34), 1.0 (referent), and 0.69 (CI, 0.45-1.06), respectively. Analysis restricted to the 7,396 women (146 cases) whose sleep duration in 1975 and 1981 were in the same duration group (stable sleepers) yielded HRs of 1.10 (CI, 0.59-2.05), 1.0, and 0.28 (CI, 0.09-0.88), with a decreasing trend (P = 0.03). This study provides some support for a decreased risk of breast cancer in long sleepers. (Cancer Res 2005; 65(20): 9595-600)

Sleep Duration and Cancer Risk: a Systematic Review and Meta-analysis of Prospective Studies

“…Finally, 12 articles fulfilling the inclusion criteria were included in the meta-analysis. Among these 12 articles, five studies reported breast cancer (Verkasalo et al, 2005;Pinheiro et al, 2006;Kakizaki et al, 2008b;Vogtmann et al, 2013;Wu et al, 2013), two studies on colorectal cancer (Jiao et al, 2013;Zhang et al, 2013), one each study on prostate cancer (Kakizaki et al, 2008a), endometrial cancer (Sturgeon et al, 2012), epithelial ovarian cancer (Weiderpass et al, 2012), thyroid cancer (Luo et al, 2013), and all type cancers (von Ruesten et al, 2012).…”

“…Two studies reported a U-shaped association between sleep duration and cancer risk (Jiao et al, 2013;Zhang et al, 2013); whereas other studies did not reveal such an association (Kakizaki et Hao Zhao 1,2,3& , Jie-Yun Yin 2& , Wan-Shui Yang 1 , Qin Qin 2 , Ting-Ting Li 2 , Yun Shi 2 , Qin Deng 1 , Sheng Wei 2 , Li Liu 2 *, Xin Wang 1 *, Shao-Fa Nie 2 * von Ruesten et al, 2012), or only found a null association (Verkasalo et al, 2005;McElroy et al, 2006;Pinheiro et al, 2006;Sturgeon et al, 2012;Luo et al, 2013). The mechanisms underlying the association between short or long sleep duration and cancer risk are not fully understood.…”

“…Overall, the total number of participants included was 723,337, with 15,156 reported cancer outcomes. Six studies were performed in USA, three in Japan (Kakizaki et al, 2008b;Weiderpass et al, 2012), and one each from German (von Ruesten et al, 2012), Finland (Verkasalo et al, 2005), and Singapore (Wu et al, 2008). The study samples ranged from 12, 222 to 142, 933, and the median of the follow-up durations is 11.3 years.…”

Modelling ‘non-visual’ effects of daylighting in a residential environment

“…Based on this information, one can infer the great importance of having a bedroom that is very dark at night for proper circadian rhythm and sleep maintenance [62][63]. This task, given streetlights, car headlights, light from other buildings, and other sources of light pollution during the night, is perhaps even more difficult to achieve architecturally than delivering the correct amounts of light during the day, especially when one adds the caveat that morning light penetration into the bedroom is desirable.…”

Sleep duration and cancer risk: time to use a “sleep-years” index?

“…Dr. Sturgeon et al [4] now provide the sixth study on the issues concerned and report mixed results. Overall, with regard to how long one sleeps, first [4][5][6][7][8]-but not all [9]-epidemiological evidence could be viewed in line with increased cancer risks in those who sleep less than others [2].…”