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 .
Underestimation of risk associations due to regression dilution in long-term follow-up of prospective studies.
In prospect i ve studies , disease rates during follow-up are typically analyzed with respect to the values of factors measured during an initial baseline survey . However , because of " regression dilution , " this generally tends to underestimate the real associations of disease rates with the " usual " levels of such risk factors during some particular exposure period . The " regression dilution ratio " describes the ratio of the steepness of the uncorrected association to that of the real association . To assess the relevance of the usual value of a risk factor during particular exposure periods ( e.g. , first , second , and third decades ) to disease risks , regression dilution ratios can be derived by relating baseline measurements of the risk factor to replicate measurements from a reasonably representative sample of study participants after an interval equivalent to about the midpoint of each exposure period ( e.g. , at 5 , 15 , and 25 years , respectively ) . This report illustrates the impact of this time interval on the magnitude of the regression dilution ratios for blood pressure and blood cholesterol . The analyses were based on biennial re measurements over 30 years for participants in the Framingham Study ( Framingham , Massachusetts ) and a 26-year resurvey for a sample of men in the Whitehall Study ( London , Engl and ) . They show that uncorrected associations of disease risk with baseline measurements underestimate the strength of the real associations with usual levels of these risk factors during the first decade of exposure by about one-third , the second decade by about one-half , and the third decade by about two-thirds . Hence , to correct appropriately for regression dilution , replicate measurements of such risk factors may be required at varying intervals after baseline for at least a sample of participants
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 .