The vast majority of studies reported inverse associations between 25(OH)D concentration and all-cause mortality .
This association appeared to be non-linear , with progressively lower mortality with increasing 25(OH)D up to a point , beyond which there was no further decrease .
There is moderate evidence that vitamin D status is inversely associated with cancer mortality and death due to respiratory diseases , while for cardiovascular mortality , there is weak evidence of an association in observational studies , which is not supported by the data from intervention or Mendelian r and omization studies .
Epidemiological evidence suggests that vitamin D deficiency is associated with increased mortality , but it is unclear whether this is explained by reverse causation , and if there are specific causes of death for which vitamin D might be important .
Serum 25-hydroxyvitamin D level, chronic diseases and all-cause mortality in a population-based prospective cohort: the HUNT Study, Norway
Objective To investigate the association of vitamin D status with  all-cause mortality in a Norwegian population and the potential influences of existing chronic diseases on the association . Design A population -based prospect i ve cohort study . Setting Nord-Trøndelag County , Norway . Participants A r and om sample ( n=6613 ) of adults aged 20 years or older in a cohort . Methods  Serum 25-hydroxyvitamin D ( 25(OH)D ) levels were measured in blood sample s collected at baseline ( n=6377 ) .  Mortality was ascertained from the Norwegian National Registry . Cox regression models were applied to estimate the HRs with 95 % CIs for all-cause mortality in association with serum 25(OH)D levels after adjustment for a wide spectrum of confounding factors as well as chronic diseases at baseline . Results The median follow-up time was 18.5 years , during which 1539 subjects died . The HRs for all-cause mortality associated with the first quartile level of 25(OH)D ( < 34.5 nmol/L ) as compared with the fourth quartile ( ≥58.1 nmol/L ) before and after adjustment for chronic diseases at baseline were 1.30 ( 95 % CI 1.11 to 1.51 ) and 1.27 ( 95 % CI 1.09 to 1.48 ) , respectively . In the subjects without chronic diseases at baseline and with further exclusion of the first 3 years of follow-up , the corresponding adjusted HR was 1.34 ( 95 % CI 1.09 to 1.66 ) . Conclusions Low serum 25(OH)D level was associated with increased all-cause mortality  in a general Norwegian population . The association was not notably influenced by existing chronic diseases
The vast majority of studies reported inverse associations between 25(OH)D concentration and all-cause mortality .
This association appeared to be non-linear , with progressively lower mortality with increasing 25(OH)D up to a point , beyond which there was no further decrease .
There is moderate evidence that vitamin D status is inversely associated with cancer mortality and death due to respiratory diseases , while for cardiovascular mortality , there is weak evidence of an association in observational studies , which is not supported by the data from intervention or Mendelian r and omization studies .
Epidemiological evidence suggests that vitamin D deficiency is associated with increased mortality , but it is unclear whether this is explained by reverse causation , and if there are specific causes of death for which vitamin D might be important .