Sleep duration and breast cancer incidence: results from the Million Women Study and meta-analysis of published prospective studies

Abstract

Study objectives To investigate the association between sleep duration and breast cancer incidence, we examined the association in a large UK prospective study and conducted a meta-analysis of prospective studies Methods In the Million Women Study, usual sleep duration over a 24-hour period was collected in 2001 for 713,150 participants without prior cancer, heart problems, stroke or diabetes (mean age=60 years). Follow-up for breast cancer was by record linkage to national cancer registry data for 14.3 years on average from the 3-year resurvey. Cox regression models yielded multivariable-adjusted breast cancer relative risks (RR) and 95% confidence intervals (CIs) for sleep duration categories. Published prospective studies of sleep duration and breast cancer risk were included in a meta-analysis, which estimated the inverse-variance weighted average of study-specific log RRs for short and for long versus average duration sleep Results After excluding the first five years to minimise reverse causation bias in the Million Women Study, 24,476 women developed breast cancer. Compared with 7-8 hours of sleep, the RRs for <6, 6, 9, and >9 hours of sleep were 1.01 (95%CI, 0.95-1.07), 0.99 (0.96-1.03), 1.01 (0.96-1.06), and 1.03 (0.95-1.12), respectively. In a meta-analysis of 14 prospective studies plus the Million Women Study, including 65,410 breast cancer cases, neither short (RR<7 hours=0.99 [0.98-1.01]) nor long (RR>8 hours=1.01 [0.98-1.04]) versus average duration sleep was associated with breast cancer risk Conclusions The totality of the prospective evidence does not support an association between sleep duration and breast cancer risk

Association of lifestyle factors and breast cancer risk in Vietnamese women: A matched case-control study

“…Our study was in line with two previous meta-analysis studies that sleeping patterns were not associated with breast cancer [37,38]. However, other meta-analyses showed that short sleep and long sleep duration signi cantly increased breast cancer risk [18,39].…”

Sleep and breast and prostate cancer risk in the MCC-Spain study

“…Findings here are similar to those of previous studies reporting no clear association of either short or long sleep duration and breast or prostate cancer risk 18 – 20 . A meta-analysis reported a RR of 1.00 (95% CI 0.94–1.08) for breast cancer risk among those with the shortest sleep duration (ranging from < 5 to ≤ 6.5 h per night) compared with medium sleep duration, and of 1.02 (95% CI 0.92–1.12) for the longest sleep duration (ranging from > 7 to ≥ 10 h per night) 19 .…”

“…Previous studies are generally inconsistent and have reported differing associations of both short 7 – 11 and long 10 , 12 , 13 sleep duration, and breast or prostate cancer risk 14 – 17 . Recent meta-analyses have reported no clear evidence of associations of either short or long sleep duration and breast or prostate cancer risk 18 – 20 .…”

Blood biomarker levels by total sleep duration: cross-sectional analyses in UK Biobank

“…However, a previous comparison between self-reported questionnaires and sleep diary data suggested a good correlation between two measurements of sleep duration (37). Furthermore, total sleep duration has been shown in the Million Women Study to be reproducible over ~2 years in women in middle or old age (38), supporting that short-term total sleep duration can be reliably reported by participants. While accelerometer data were only collected in one-fifth of the UK Biobank cohort, future studies should explore the associations in this subset of participants with the use of accelerometer-derived sleep parameters, which itself is also a rapidly evolving research area.…”