Long-term sleep habits and the risk of breast cancer among Chinese women: a case–control study

Abstract

Previous observational studies have inconsistently suggested that poor sleep is a novel risk factor for breast cancer (BC). However, these studies mainly focused on sleep duration; other sleep domains were rarely reported. The aim of this study was to evaluate the association of a broad range of sleep domains with the risk of BC incidence. We used a community-based 1 : 1 individual matched case-control design that included 401 female patients with incident BC and 401 age-matched and area-matched female controls in Jiujiang, China. Long-term sleep habits were assessed comprehensively using a validated 17-item Sleep Factors Questionnaire. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression. Light exposure at night (highest vs. lowest level, aOR=1.19, 95% CI: 1.06-2.68), habitual timing of sleep (after 12 a.m. midnight vs. before 22 p.m., aOR=1.12, 95% CI: 1.03-2.62), night/shift work (yes vs. no, aOR=1.38, 95% CI: 1.04-2.71), and frequency of night-time wakings (>2 per night vs. never, aOR=1.21, 95% CI: 1.10-2.96) were associated with an increased risk of BC after mutually adjusting for other sleep parameters. These positive associations remained irrespective of menopausal status and tumor estrogen receptor status. There was no association between sleep duration, sleep quality, sleep medication use, insomnia frequency, daytime nap, and the risk of BC. Our results indicate that sleep problems including light exposure at night, night/shift work, late sleeping, and frequent night waking could increase the risk of BC development, independent of other sleep factors.

XRCC5/6 polymorphisms and their interactions with smoking, alcohol consumption, and sleep satisfaction in breast cancer risk: A Chinese multi‐center study

“…The identification of risk factors and susceptible populations of breast cancer has become imperative in China given the recent marked increase of breast cancer cases among Chinese women 1,2 . Epidemiological studies identified cigarette smoking, alcohol consumption, and sleep disorders among the several environmental risk factors for breast cancer 3–5 . Nevertheless, only a small proportion of exposed people develop breast cancer, suggesting that breast cancer incidence is not only correlated with environmental factors, but also with genetic susceptibility.…”

Light at night and risk of breast cancer: a systematic review and dose–response meta-analysis

“…Table 1 presents characteristics of the 17 included studies, three with case-cohort design [ 40 – 42 ], six cohort [ 23 – 25 , 43 – 45 ], and eight case–control [ 46 – 53 ]. The studies were published during 2001–2021, mainly in North America (N = 10), followed by Europe (N = 3), Israel (N = 2), Australia (N = 1), and China (N = 1).…”

Women's health and night shift work: Potential targets for future strategies in breast cancer (Review)

“…This investigation also showed that sleep quality, well-known to be influenced by occupational features ( 42 ), is also linked to the state of menopause. However, no association was found between BC risk and sleep duration, sleep quality, use of sleep medication, frequency of insomnia and daytime napping in a case-controlled study conducted in China ( 65 ). This research showed that night shift work and frequency of nocturnal awakenings were associated with an increased risk of BC independently from menopausal status and tumour estrogen receptor status.…”

“…However, even with regard to this proposed mechanism, the studies have shown contested results; a case-controlled study performed in Vancouver found no association between nocturnal artificial light and BC ( 64 ); whereas a case-controlled study performed in China ( 65 ) and a population-based case-controlled study in Spain ( 66 ) both showed that there was an increased risk of BC associated with exposure to night light, in particular, with external light in the blue spectrum.…”