Vitamin D status and its longitudinal association with changes in patterns of sleep among middle-aged urban adults

Abstract

Objective: We examined relationships of vitamin D status with over time changes in patterns of sleep in a longitudinal study of Whites and African-American urban middle-aged adults, while further testing effect modification by age group, sex and race and the potential roles of dietary and supplemental vitamin D.

Methods: Data on 1,760 middle-aged participants in the Healthy Aging in Neighborhoods of Diversity Across the Life Span (HANDLS study: Age range at v₂: 33-71y, mean±SD:53.0±8.8, % women: 58.4%, % African-American:60.3%) were used, with complete baseline 25-hydroxyvitamin D [25(OH)D] serum concentration data, initial selected covariates and mediators, and initial and/or follow-up data on five sub-scales (sleep duration, daytime dysfunction, sleep disturbance, sleep latency and sleep quality) of the Pittsburgh Sleep Quality Index. Mean±SD time between initial and follow-up visits: 4.1±1.5 years. Time-interval multiple mixed-effects linear regression models were used.

Results: Upon multiple testing adjustment, among Whites, initial 25(OH)D was associated with better sleep duration [25(OH)D × TIME γ±SE: -0.027±0.011, P=0.017] and sleep quality [25(OH)D × TIME γ±SE: -0.026±0.010, P=0.008] over time, with heterogeneity by race found for both relationships (P<0.05 for 25(OH)D × TIME × Race in the un-stratified model). These relationships remained unaltered after further adjustment for dietary and supplemental vitamin D, indicating that this association may be largely explained by sunlight exposure.

Limitations: Limitations included small sample size, selection bias, residual confounding and lack of objective sleep measures. Conclusions Vitamin D status, possibly through mechanisms involving sunlight exposure, was linked to a potential improvement in sleep duration and quality among White urban adults.

Keywords: Adults; Diet; Racial disparities; Sleep; Supplements; Vitamin D status.

Figure 1.

Participant Flowchart: HANDLS 2009–2017 Abbreviations: 25(OH)D=25-hydroxyvitamin D; PSQI=Pittsburgh Sleep Quality Index; HANDLS=Healthy Aging in Neighborhoods of Diversity Across the Life Span; v0=visit 0; vl=visit 1; v2=visit 2.

Figure 2A.

Predictive margins for (A.l.) sleep duration and (A.2.) sleep quality PSQI sub-scales across V₁ 25(OH)D levels among Whites: HANDLS 2009–2017 Abbreviations: 25(OH)D=25-hydroxyvitamin D; PSQI=Pittsburgh Sleep Quality Index; HANDLS=Healthy Aging in Neighborhoods of Diversity Across the Life Span; v_l=visit 1; v₂=visit 2. Note: PSQI sub-scale scores reflected worse outcome with higher score.

Figure 2B.

Biological mechanisms for association between vitamin D and sleep Abbreviations: CNS=Central Nervous System; CYP24al=Cytochrome P450 Family 24 Subfamily A Member 1; CYP27bl=Cytochrome P450 Family 24 Subfamily B Member 1; GDNF=Glial Cell Derived Neurotrophic Factor; NGF=Neural Growth Factor; NT3=Neurotrophin-3; NT4=Neurotrophin-4; RXR=Retinoid-X receptor; THP-2=Tryptophan Hydroxylase Protein-2; VDR=Vitamin D receptor; VDRE=Vitamin D response element; Note: Figure created in Biorender, http://www.biorender.com Source: (Muscogiuri et al., 2019)