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Duration of sleep and breast cancer risk in a large population‐based case–control study
Author(s) -
McELROY JANE A.,
NEWCOMB POLLY A.,
TITUSERNSTOFF LINDA,
TRENTHAMDIETZ AMY,
HAMPTON JOHN M.,
EGAN KATHLEEN M.
Publication year - 2006
Publication title -
journal of sleep research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 117
eISSN - 1365-2869
pISSN - 0962-1105
DOI - 10.1111/j.1365-2869.2006.00523.x
Subject(s) - breast cancer , odds ratio , melatonin , medicine , case control study , sleep (system call) , population , cancer , oncology , circadian rhythm , demography , gynecology , physiology , environmental health , sociology , computer science , operating system
Summary One important function of sleep may be its contribution to the maintenance of the immune system and regulation of the circadian rhythms by melatonin. Researchers have speculated that disruption of immune functions involving cortisol levels and natural killer cell activity may increase breast cancer risk whereas increased melatonin exposure may protect against breast cancer. We conducted a multistate population‐based case–control study of 4033 women with invasive breast cancer and 5314 community women without breast cancer in which we inquired about women's sleep habits in the recent past and during adult lifetime. Relative to women who slept 7.0–7.9 h/night, the multivariate odds ratio for developing breast cancer among women who slept an average of 9 h or more per night approximately 2 years prior to interview was 1.13 (95% CI 0.93–1.37). The multivariate‐adjusted odds ratio for the continuous term was 1.06 (95% CI 1.01–1.11), suggesting a 6% increase in risk for every additional hour of sleep. Similar patterns were observed for average lifetime adult sleep duration. We found little evidence that sleeping few hours per night was associated with breast cancer risk. The results of this study suggest that increasing sleep duration is modestly associated with an increased breast cancer risk. In contrast, short duration of sleep (<7 h/night) is not substantially associated with increased risk. Further research in this area is warranted.