Vitamin D Status Over Time and Cognitive Function in Norwegian Older Adults: A Prospective Cohort of the HUNT Study

摘要

BACKGROUND: There is conflicting evidence regarding the association between vitamin D status and cognitive function in population studies. The use of one-time vitamin D measurement in cognitive health studies may not reflect long-term vitamin D status in the body. OBJECTIVE: We aimed to examine the relationship of vitamin D status measured over time with the risk of neurocognitive disorders (NCDs) in Norwegian older adults. DESIGN: Prospective cohort study. SETTING: Regional, Trondelag Health Study. PARTICIPANTS: This study followed a random cohort of 717 participants from HUNT2 (1995-97) and HUNT3 (2006-08) to HUNT4 70+ (2017-19). The mean age at HUNT4 70+ was 77.7 years. METHODS: Seasonal-standardized serum 25-hydroxyvitamin D 25(OH)D levels in HUNT2 and HUNT3 were averaged and used as either a categorical variable (< 50 and GE;50 nmol/L) or a continuous variable (per 25 nmol/L decrease). In the cohort aged 70 years or over (HUNT4 70+), NCDs consisting of mild cognitive impairment (MCI) and dementia were diagnosed by clinical experts according to the DSM-5 criteria. Logistic and linear regression models were used to estimate odds ratios (ORs) and regression coefficients (beta) with 95 confidence intervals (CIs) to assess the relationship between 25(OH) D levels and the risk of NCDs or the Montreal Cognitive Assessment (MoCA) score. RESULTS: In total, 347 (48.4) had NCDs in HUNT4, with 33.3 having MCI and 15.1 having dementia. Compared with participants with serum 25(OH)D GE;50 nmol/L, those with 25(OH)D < 50 nmol/L had a similar risk of NCDs (OR 1.05, 95 CI 0.76 to 1.46). No association was observed with the risk of MCI (OR 1.01, 95 CI 0.71 to 1.44) or dementia (OR 1.16, 95 CI 0.70 to 1.92), respectively. In a subsample of participants evaluated with the MoCA (n=662), a 25 nmol/L decrease in serum 25(OH)D was not associated with a change in MoCA score (beta 0.33, 95 CI -0.17 to 0.85). CONCLUSION: Vitamin D insufficiency defined by two times measurements of serum 25(OH)D with a 10-year interval was not associated with the risk of NCDs in a cohort of older Norwegian adults. Future studies utilizing multiple vitamin D measurements with a longer follow-up duration and larger sample size are warranted.