Cross-sectional correlates and prospective longitudinal risk factors of impaired sleep
Creators: name: Eid, Shireen Walid
Publisher: name: The Australian National University
Year: 2019
Subjects: Objective sleep measures
steps
caffeine intake
alcohol intake
overweight
physical activity

description: Background and aims: Many factors are reported to interfere with sleep in otherwise healthy adults, including overweight/obesity and related factors (e.g. physical inactivity, disordered eating). Conversely, sleep impairment has been shown to change eating and exercise habits and contribute to weight gain over time. However, most prior relevant studies have been cross-sectional in nature and rarely accounted for potential risk factors. Fewer studies have examined a large pool of potential predictors in a prospective longitudinal study to determine which can most strongly predict impaired sleep. Thus, consistent with the relevant literature, the aim of this thesis was to examine multiple potential risk factors including demographics, symptoms/disorders, physical activity, other behaviour (e.g. substance use, electronic device use) and work-contexts as predictors of sleep at T1 (cross-sectional) and 3-months later (T2, longitudinal), in a community sample. In study 1, the Pittsburgh Sleep Quality Index (PSQI) total score was used to assess sleep quality. In study 2, PSQI sub-scale scores were used to examine the components of sleep quality. In study 3, the predictors of actigraphy-derived measures of sleep were examined. In study 4, the cross-sectional and longitudinal predictors of body mass index (BMI) and waist to hip ratio (WHR) were examined, as proxy measures of overweight/obesity. Method: A community-derived sample of Australian adults completed two online questionnaires, 3-months apart (T1: n=161; T2: n=155), which asked about demographics, sleep, night-eating, affective distress (i.e., stress, anxiety, depression), physical activity, substance use (i.e., caffeine, alcohol, drugs), work-context (e.g., shift-work) and parenting young children. Physical activity and sleep were also monitored over 24-hours using actigraphy at T1 and T2. Results: Study 1 results showed that poor sleep quality at T1 was predicted by more night-eating, depression, and recreational drug use, but no factors predicted sleep quality at T2, after controlling for T1 sleep. A bidirectional relationship was detected between T1 sleep quality and T1 night-eating, and it almost predicted it at T2. Study 2 results showed that demographics (female gender), symptoms/disorders (high BMI, depression, fatigue), other behaviour (watching TV, electronic device use), and physical inactivity (lack of domestic activity) predicted impairment in the components of sleep quality at T1 and T2. Study 3 results showed that impairment in sleep at T1 was predicted by physical inactivity, including total number of steps, METs, and time spent travelling, along with less education. At T2, longer sleep onset latency was predicted by parenting young children and watching TV at night; shorter sleep duration was predicted by female gender; and longer awake time and less sleep efficiency were predicted by less alcohol intake. Study 4 results showed that at T1 high BMI/WHR and overweight/obesity were predicted by older age, male gender, cold ambient temperature, more sleep disturbances, sleep medication use, and domestic physical activity. At T2, high WHR was predicted by older age, male gender, cold ambient temperature, and full-time employment, after controlling for T1 WHR and demographics. Conclusion: Taken together, the results suggest that few modifiable risk factors for impaired sleep were detected, including only watching TV and overweight/obesity. Additionally, few modifiable risk factors for overweight/obesity were detected including only changing employment conditions. Taken together with the results of Studies 1-3, they provide support for the assertion that a vicious cycle of escalating night-eating and sleep problems may develop in overweight/obese people which contributes to weight gain over time, in otherwise healthy adults.