Comprehensive assessments of long-term sleep habits in epidemiological study: Validity and reliability of sleep factors questionnaire (SFQ) among Chinese women
Introduction
Accumulating epidemiological evidences indicate that sleep duration is a potentially novel risk factor for some chronic diseases such as obesity [1], type 2 diabetes (T2D) [2], hypertension [3], and breast cancer (BC) [4], although the results have not been entirely consistent. In addition to sleep duration per se, other sleep domains including habitual timing of sleep, frequency for nighttime wakings, nighttime lighting conditions, sleep noise, nap time, sleep medications use, night/shift work, and sleep quality have also been suggested to modify the risk of several chronic diseases. For instance, light exposure at night (LAN) could be associated with an increased risk of incident BC by decreasing the production of melatonin by the pineal gland [4]; rotating night/shift work may alter the risk of cardiovascular diseases (CVDs) through disrupting circadian rhythmicity and autonomic balance [5]; sleep noise might increase risks of developing BC [6], T2D [7], adiposity [8], and CVDs [9]; and poor sleep quality has also been recognized to be associated with several health outcomes including BC [4], T2D [10], obesity [11], and hypertension [12]. Thus, when investigating the association between a certain sleep parameter and a health outcome in epidemiological study, other sleep variables should be measured and considered as potential confounders.
Therefore, accuracy of the comprehensive assessments of sleep factors including sleep quantity, sleep quality, and other habitual sleep factors, although it remains a challenging task, plays a key role in evaluating the effects of sleep. However, none of questionnaires, to our knowledge, has been designed to collect a broad range of sleep parameters in various aspects among previous sleep epidemiological researches for chronic diseases; most are only focused on sleep duration, and very few [13] have examined the validity of self-reported sleep duration, let alone the accuracy of other sleep domains except sleep duration.
Additionally, previous validation researches often used objective measures such as wrist actigraphy—a validated activity monitor for sleep assessment [14], and polysomnography—the gold standard for estimating sleep [15]. In this situations, the monitoring results are derived within a short time period (several days to weeks), which may ignore night-to-night variations and thus cannot represent long-term sleep habits. Unlike clinical researches, this issue is important in epidemiological studies as we usually assume that the long-term habitual behaviors and lifestyle may alter the risk of the disease development.
With these in mind, we developed a 17-item sleep factors questionnaire (SFQ) to systematically collect sleep factors including sleep duration, sleep quality, LAN exposure, nap time, night/shift work, the use of sleeping pills, habitual timing of sleep, and frequency of nighttime wakings for the Jiujiang Breast Cancer Study (JBCS) in Jiujiang, China. The aim of present study was to evaluate the reliability and validity of SFQ implemented in the JBCS project. Accounting for night-to-night variations and seasonal effect, four quarterly 30 consecutive days (a total of 120 days) sleep diaries were used to validate the SFQ.
Section snippets
The sleep factors questionnaire (SFQ)
The questionnaire was based on the SFQ used in the JBCS. JBCS is an ongoing population-based case-control study to assess the risk of female breast cancer (BC) associated with sleep factors and other potential risk factors in Jiujiang City, China. JBCS was initiated in 2013 and plan to recruit 2000 incident female BC cases and 2000 age-matched healthy female controls. The source population for the JBCS was the female permanent residents aged 18–74 years in seven communities in Xunyang District,
Subject characteristics
There were no statistically significant differences in the distribution of demographic and behavioral characteristics including age, education, income, smoking status, and alcohol use between the present validation study participants and the parent JBCS project (data not shown).
Between November 2014 and December 2015, among 100 enrolled participants, all of them completed both the baseline SFQ (SFQ-1) and the retest administrations of the SFQ (SFQ-2); 2 did not return sleep diary in the second
Discussion
In this validation study over a 1-year period among 100 Chinese middle-aged well-educated women, we found that the 17-item SFQ which was designed to comprehensively evaluate long-term sleep habits in the JBCS project could provide reproducible and valid results for most sleep parameters. As the need for comprehensive assessments of sleep in epidemiological studies, findings from this investigation have important implications for future sleep research.
We are not aware of any prior studies
Conflict of interest
None.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (Grant numbers 81460514 and 81560553), and the Natural Science Foundation of Jiangxi Province, China (Grant numbers 20151BAB205065 and 20142BAB205017).
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