The relationship between vitamin D deficiency and mortality in older adults before and during COVID-19 pandemic

BACKGROUND: Vitamin D is an essential fat-soluble vitamin thought to be associated with chronic diseases, mortality and COVID-19. OBJECTIVE: To investigate the association between 25(OH) vitamin D levels and mortality of chronic diseases in subjects aged ≥65 years before and during COVID-19 pandemic. METHODS: A single-center, retrospective study was performed using the hospital database of subjects aged 65 years and older who had undergone vitamin D measurement between 01.01.2019 and 31.12.2021. All patients with vitamin D measurement (N = 2155) were followed as a cohort from the date of serum vitamin D analysis through death date or 01.01.2022. Age, gender, chronic diseases, survival status, date of death of the deceased, laboratory values including complete blood count, liver/renal functions and 25(OH) vitamin D levels were all noted. Subjects were classified into three groups according to their 25(OH) vitamin D levels; severe deficient group (<10 ng/ml), moderate deficient group (10–19.9 ng/ml), and control group (≥20 ng/ml). RESULTS: Data of 1949 subjects were included in this retrospective analysis and 206 of them (10.6%) had at least two vitamin D measurements. Until the time of data collection (01.01.2022), 94 of the cases had died within the last three years, and only five of them had repeated measurements. While the mean vitamin D level was lower, age and frequency of dyslipidemia, coronary artery disease (CAD), chronic obstructive pulmonary disease (COPD), arrhythmia, dementia and severe vitamin D deficiency (<10 ng/ml) were higher in subjectswho died (all p<0.05). According to the Cox proportional hazards model; age, presence of CAD, COPD, arrhythmia, dementia, anemia and severe vitamin D deficiency were independently related with mortality (all p<0.05). After adjusted by age, gender, and comorbidities, the probability of death was found to be 1.91 (95% CI=1.12–3.24) times higher in the severe vitamin D deficient group. CONCLUSIONS: The results of this study have shown that - after having adjusted for potential factors - severe vitamin D deficiency (<10 ng/ml) seems to be an independent predictor for non-cancer mortality. Although vitamin D measurement/treatment is very easy and cheap where, on the contrary, severe vitamin D deficiency can be quite mortal.