Abstract
ObjectivesTo investigate the descriptive nature of objectively-measured, free-living sleep quantity and quality, and the relationship to adiposity, in a rural African setting in 145 adults (≥ 40 years, female: n = 104, male: n = 41). Wrist-mounted, triaxial accelerometry data was collected over 9 days. Measures of sleep quantity and quality, and physical activity were extracted from valid minute-by-minute data. Adiposity indices were body-mass-index, waist circumference and conicity index. Self-reported data included behavioural, health and socio-demographic variables. Community consultation followed the quantitative data analyses, for validation and interpretation of findings.ResultsFemales had more nocturnal sleep than males (7.2 vs. 6.8 h/night, p = 0.0464) while males recorded more diurnal sleep time (p = 0.0290). Wake after sleep onset and number of awakenings were higher in females, and sleep efficiency was higher in males (p ≤ 0.0225). Sleep indices were generally similar between weekdays and weekends, except for sleep fragmentation index (p = 0.0458). Sleep quantity, but not sleep quality was independently and inversely associated with adiposity (p = 0.0453). Physical activity and morbidity measures were significantly and consistently associated with sleep and adiposity measures (p < 0.0458). The preliminary qualitative data suggests that future studies should include more detailed data around contextual issues of sleep (social, cultural, economic, environment).
Highlights
Sleep is recognized as an important lifestyle contributor to morbidity and mortality [1]
Wake after sleep onset and number of awakenings were higher in females, and sleep efficiency was higher in males (p ≤ 0.0225)
While extensive Sleep Health Epidemiology literature exists for high income countries, there is a need of especially objective measures of sleep, such as actigraphy, from low and middle-income countries, [2, 3]
Summary
Sleep is recognized as an important lifestyle contributor to morbidity and mortality [1]. Within the South African context to date, studies have exclusively utilized self-report measures in adult populations [4–12]. There is a dearth of objectively-measured sleep data from South African, and rural African settings [3, 13]. Self-reported long sleep time for rural South Africans [8– 10], requires confirmation using objective measures of sleep duration. A recent study found a significant, inverse relationship between self-reported sleep duration and adiposity in a rural African setting [14]. Given the lack of objectively-measured, free-living sleep parameters in any South African setting, the objective of this study was to use wrist-actigraphy to derive sleep parameters in a rural African setting during a cross-sectional survey, and extend the findings of self-report sleep duration and the relationship to adiposity [4–12, 14]
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