Low Vitamin D Levels Linked to Earlier Death

In that increasing age and parathyroid hormone levels both have positive relationships with the risk of death, and inverse relationships with vitamin D levels, Nguyen Nguyen, from the Garvan Institute of Medical Research (Australia), and colleagues studied whether vitamin D levels may be independently associated with mortality. The team reviewed data collected in the Dubbo Osteoporosis Epidemiology Study, which has been following 1,358 women and 858 men in the city of Dubbo, near Sydney, Australia, since 1989.  They randomly selected 413 men who were older than 60 in 1989 and assessed their age, weight, height, history of falls and fractures, and lifestyle factors such as smoking and alcohol consumption, over a 14-year period starting in 1996. The researchers also evaluated blood samples, taken at the study’s start, for both parathyroid hormone and vitamin D and correlated them with the mortality rate in the study group over the study period. During the study follow-up period, 200 of the men died, with most being significantly older and showing significantly lower circulating Vitamin D [25(OH)D] levels that were categorized as insufficient.  Noting that the prevalence of deficiency among the living participants was 8%, as compared with 18% among those who had died, with 42% of both groups having insufficient levels, the researchers observed that half of the living men had sufficient vitamin D, compared with 40% of those who had died.  Further data analysis revealed that for each standard deviation increase in circulating Vitamin D levels, the risk of death fell by 19%.   Compared with those who were deficient in circulating Vitamin D, those who had insufficient levels had a 36% decrease in the risk of death; whereas those who had sufficient levels of circulating Vitamin D had a 39% decrease in the risk of death, as compared with those who were deficient.