A meta-analysis of individual participant data of eight prospective cohort studies from Europe and the US has investigated the association between serum 25-hydroxyvitamin D concentrations [ 25(OH)D ] and mortality in a large consortium of cohort studies paying particular attention to potential age, sex, season, and country differences.
Participants were 26 018 men and women aged 50-79 years
The main outcome measure was all-cause, cardiovascular, and cancer mortality.
25(OH)D concentrations varied strongly by season ( higher in summer ), country ( higher in US and northern Europe ) and sex ( higher in men ), but no consistent trend with age was observed.
During follow-up, 6695 study participants died, among whom 2624 died of cardiovascular diseases and 2227 died of cancer.
For each cohort and analysis, 25(OH)D quintiles were defined with cohort and subgroup specific cut-off values. Comparing bottom versus top quintiles resulted in a pooled risk ratio of 1.57 for all-cause mortality.
Risk ratios for cardiovascular mortality were similar in magnitude to that for all-cause mortality in subjects both with and without a history of cardiovascular disease at baseline.
With respect to cancer mortality, an association was only observed among subjects with a history of cancer ( risk ratio, RR=1.70 ).
Analyses using all quintiles suggest curvilinear, inverse, dose-response curves for the aforementioned relationships.
No strong age, sex, season, or country specific differences were detected.
Heterogeneity was low in most meta-analyses.
In conclusion, despite levels of 25(OH)D strongly varying with country, sex, and season, the association between 25(OH)D level and all-cause and cause-specific mortality was remarkably consistent.
Results from a long term randomised controlled trial addressing longevity are being awaited before vitamin D supplementation can be recommended in most individuals with low 25(OH)D levels. ( Xagena )
Schöttker B et al, BMJ 2014;348:g3656