Independent And Joint Associations Of Cardiorespiratory Fitness And Body Mass Index With Sleep Quality And Duration In Older Adults

PURPOSE: Little research has evaluated the independent and combined associations of cardiorespiratory fitness (CRF) and body mass index (BMI) on sleep outcomes in older adults. METHODS: This cross-sectional study included 819 older adults aged ≥65 years (58% female). CRF was measured by 400 m walk test and categorized into sex-specific quartiles (Q1-Q4). BMI was calculated as kg/m2 and categorized as normal weight, overweight, or obese. Self-reported sleep quality (SQ) was assessed via the Pittsburgh Sleep Quality Index (score ≥ 5 indicative of poor sleep). Objectively measured sleep duration was assessed via smart watch, and sufficient sleep duration (SSD) was defined as 7-8 hours following the CDC guidelines for older adults. Logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) of poor SQ or SSD. For joint analyses, participants were categorized as fit (Q2-Q4) vs unfit (Q1) and normal weight vs overweight or obese. All models were adjusted for sex, age, education, marital status, alcohol intake, smoking, physical activity, depression, anxiety, comorbidities, sleep medication use, and CRF or BMI. RESULTS: In this cohort, 34% (n = 277) had poor SQ and 35% (n = 269) had SSD. Compared to low CRF (Q1), ORs (95% CIs) of poor SQ were 0.92 (0.58-1.46) for Q2, 1.22 (0.76-1.98) for Q3, and 1.03 (0.60-1.74) for Q4 after adjusting for confounders including BMI. Compared to normal weight, ORs (95% CIs) were 1.04 (0.73-1.50) and 1.05 (0.68-1.62) in overweight and obese, respectively after adjusting for confounders including CRF. Corresponding ORs (95% CIs) of SSD were 1.29 (0.80-2.09) for Q2, 1.98 (1.19-3.28) for Q3, 1.78 (1.03-3.07) for Q4, and 0.93 (0.65-1.33) for overweight, and 0.70 (0.45-1.10) for obese after adjusting for confounders including BMI or CRF for each other. In joint analysis, compared to ‘unfit and overweight/obese,’ fit older adults had higher prevalence of SSD in both overweight/obese (OR = 1.65, 95% CI = 1.04-3.28) and normal weight (OR = 1.99, 95% CI = 1.20-3.28). However, no significant results were observed in self-reported poor SQ in joint analysis. CONCLUSION: CRF, but not BMI, was associated with objectively measured SSD, but not self-reported SQ in older adults. However, prospective studies are required.