Aspects of Vitamin D Deficiency in Elderly People in Nursing Homes and in Patients with Type 2 Diabetes : with Emphasis on Mortality, Cardiovascular Morbidity and Mental Health

Abstract: BackgroundInstitutionalised elderly people living in northern latitudes may be at elevated risk for vitamin D deficiency. They are recommended to take oral vitamin D supplements, but the main source of vitamin D is sunlight. Previous studies have shown an association between low levels of vitamin D and several diseases, but important knowledge about vitamin D in elderly people in nursing homes and in patients with type 2 diabetes is lacking. The aims of this thesis were to study aspects of vitamin D deficiency in these two populations and to explore whether low vitamin D levels were associated with mortality, cardiovascular morbidity and mental health. Also, we aimed to examine whether an intervention with encouragement to spend time outdoors during summer could increase vitamin D levels in the elderly in nursing homes.MethodsThe present thesis is based on four papers. Papers I and IV are confined to nursing home residents >65 years. Paper I is based on data from SHADES (The Study of Health and Drugs in the Elderly). Paper IV is based on the study Sunlight and Vitamin D in Older People in Nursing Homes. Papers II and III are based on data from CARDIPP (Cardiovascular Risk Factors in Patients with Diabetes—a Prospective Study in Primary Care), with patients with type 2 diabetes aged 55-66 years. Papers I-III were prospective observational cohort studies and Paper IV was a cluster randomised intervention trial.In Paper I, serum 25-hydroxyvitamin D3 (25(OH)D3) was analysed on three occasions. The vital status of the subjects was ascertained and hazard ratios (HRs) for mortality according to baseline 25(OH)D3 quartiles (Q) were calculated.In Paper II, serum 25(OH)D3 was analysed at baseline. HRs for the first myocardial infarction, stroke or cardiovascular mortality according to 25(OH)D3 were calculated.In Paper III, serum 25(OH)D3 was analysed at baseline. The SF-36 questionnaires measuring vitality and mental health were administered at baseline and after four years.In Paper IV, the intervention group was encouraged to go outside for 20-30 minutes every day for two months during the summer of 2018. Before and after the summer, serum 25(OH)D was analysed and SF-36 questionnaires measuring vitality and mental health were administered.ResultsIn Paper I, 80% of the participants had 25(OH)D3 < 50 nmol/l. Vitamin D deficiency was associated with an increased mortality risk. Compared with Q4 (25(OH)D3 >48 nmol/l), the HR (with a 95% confidence interval (CI)) for mortality was 2.02 (1.31-3.12) in Q1 (25(OH)D3 <29 nmol/l) (p<0.05), 2.03 (1.32-3.14) in Q2 (25(OH)D3 30-37 nmol/l) (p<0.05) and 1.6 (1.03-2.48) in Q3 (25(OH)D3 38-47 nmol/l) (p<0.05).In Paper II, serum 25(OH)D3 was inversely associated with the risk of cardiovascular morbidity and mortality. The HR per nmol/l was 0.98 (95% CI: 0.96-0.99) (p=0.001), when adjusted for age, sex and season.In Paper III, serum 25(OH)D3 was inversely associated with poor mental health at baseline. The odds ratio (OR) for 10 nmol/l increase in 25(OH)D3 was 0.90 (95% CI: 0.83-0.96) (p=0.003), but not at follow-up (p>0.05). Serum 25(OH)D3 was not associated with vitality at baseline (p>0.05), nor at follow-up after adjustments.In Paper IV, the 25(OH)D levels increased significantly in the intervention group during the summer: from a median (interquartile range (IQR)) of serum 25(OH)D of 42.5 (23.0) nmol/l to 53.5 (33.0) nmol/l (p=0.011). The 25(OH)D levels increased in the control group as well, but the increase was not significant. The intervention group reported better mental health after the summer compared to before the summer (p=0.015), unlike the control group.ConclusionsLow vitamin D levels were associated with increased mortality in elderly people in nursing homes, and with cardiovascular morbidity/ mortality and poor mental health in patients with type 2 diabetes. From our studies, we cannot draw conclusions about causality. The results indicate that the vitamin D levels give prognostic information. Active encouragement to spend time outdoors during summer improved the vitamin D levels and mental health in elderly people in nursing homes, and such activity could be considered as a complement to oral vitamin D supplementation in the summer.