Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements .
The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics .
However , for vitamin D2 supplementation , increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods .
Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease , cancer , and other causes .
Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with  mortality from cardiovascular , cancer , or other conditions  , under various circumstances .
Low serum 25-hydroxyvitamin D levels are associated with increased all-cause mortality risk in a general population: the Tromsø study.
OBJECTIVE Ecologic and observational studies have suggested an association between serum 25-hydroxyvitamin D ( 25(OH)D ) levels and cardiovascular disease ( CVD ) risk factors , CVD mortality , and cancer mortality . Based on this , low serum 25(OH)D levels should be associated with higher all-cause mortality in a general population . This hypothesis was tested in the present study . DESIGN The Tromsø study is a longitudinal population -based multi purpose study initiated in 1974 with focus on lifestyle-related diseases . Our data are based on the fourth Tromsø study carried out in 1994 - 1995 . METHODS Information about death and cause of death was registered by obtaining information from the National Directory of Residents and the Death Cause Registry .  Serum 25(OH)D  was measured in 7161 participants in the fourth Tromsø study . Results are presented for smokers ( n=2410 ) and non-smokers ( n=4751 ) separately as our immunoassay seems to overestimate 25(OH)D levels for smokers . RESULTS During a mean 11.7 years of follow-up , 1359 ( 19.0 % ) participants died . In multivariate regression models , there was a significantly increased risk of all-cause mortality ( hazard ratio ( HR ) 1.32 , confidence interval ( CI ) 1.07 - 1.62 ) among non-smoking participants in the lowest 25(OH)D quartile when compared with participants in the highest quartile . Equivalent results for smokers were not significant ( HR 1.06 , CI 0.83 - 1.35 ) . CONCLUSIONS Low serum 25(OH)D levels were associated with increased all-cause mortality for non-smokers , but the results did not reach statistical significance for smokers . However , low 25(OH)D levels are known to be associated with impaired general health , and r and omized controlled studies are needed to address the question of causality
Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements .
The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics .
However , for vitamin D2 supplementation , increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods .
Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease , cancer , and other causes .
Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with  mortality from cardiovascular , cancer , or other conditions  , under various circumstances .