Associations of Vitamin D Intake and Sleep Quality With Cognitive Dysfunction in Older Adults With Heart Failure

Background: Low vitamin D intake and poor sleep quality are independently associated with cognitive dysfunction in healthy older adults. However, the relationships among vitamin D intake, sleep quality, and cognitive dysfunction are unknown in older adults with heart failure (HF). Purpose: The aim of this study was to determine the relationships of vitamin D intake and sleep quality with cognitive dysfunction in older adults with HF. Methods: A total of 160 older adults with HF completed the Mini-Mental State Examination to assess cognitive function. Vitamin D deficiency was defined as less than 15 mcg/day of average intake determined using a 3-day food diary and use of dietary supplements. Sleep quality was measured by the Pittsburgh Sleep Quality Index (PSQI). Hierarchical regressions and mediation analysis were used for data analysis. Results: Thirty-four patients (21.2%) had severe cognitive dysfunction (total Mini-Mental State Examination score <= 19), 88 (55%) had vitamin D deficiency, and 120 (75%) reported poor sleep quality (total PSQI score 9 5). Increased daily vitamin D intake (beta = 0.305, P < .001) and poorer sleep quality indicated by the total PSQI score (beta = -0.312, P < .001) were associated with cognitive function. Vitamin D deficiency was associated with poor sleep quality (odds ratio, 2.22; P = .033). In mediation analysis, the relationship between vitamin D deficiency and cognitive function was mediated by sleep quality among older adults with HF. Conclusions: Both vitamin D deficiency and poor sleep quality are associated with cognitive dysfunction in older adults with HF. Interventions should be tested to target patients with poor sleep quality to improve cognitive function, particularly in those with vitamin D deficiency.