Frost SA, Nguyen T, Bliuc D, et al. Effects of vitamin D deficiency and high parathyroid hormone on mortality risk in elderly men. American Society for Bone and Mineral Research (ASBMR) 2010; Abstract 1168.
http://www.asbmr.org/itinerary/presentationdetail.aspx?id=c481d5f4-0da5-...
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2010 Abstracts Book Final. p S51-S52.
1168
Effects of Vitamin D Deficiency and High Parathyroid Hormone on Mortality Risk in Elderly Men.
Steven Frost1, Tuan Nguyen2, Dana Bliuc2, John Eisman2, Jacqueline Center2, Nguyen Nguyen*2. 1University of Western Sydney, Australia, 2Garvan Institute of Medical Research, Australia
Vitamin D deficiency is common in the elderly. Recent data have suggested that mortality risk is elevated in men with low vitamin D levels; however, the relationship could be confounded by parathyroid hormone (PTH) which had previously been shown to be associated with mortality. Therefore, this study sought to examine the inter-relationship between vitamin D and PTH levels on the risk of mortality in men.
The study was part of the Dubbo Osteoporosis Epidemiology Study, which involved 413 men aged 60+ years as at 1989, whose health status had been continuously monitored for 14 years with biannual visits. During the follow-up period, mortality was ascertained. Vitamin D was measured by 25(OH)D using an in-house pre-extraction competitive binding protein assay with charcoal separation, with an inter-assay CV of 12%. Vitamin D status was classified in 3 groups: deficient (25(OH)D,50nmol/L), insufficient (50-75nmol/L) and sufficient (>75nmol/L). PTH was measured by a solid phase two-site immunoenzymometric assay also from Diagnostics Products, with an inter-assay CV of 6%. The association between vitamin D and mortality was analyzed by the Cox’s proportional hazards model with adjustment for covariates.
The overall prevalence of vitamin D deficiency was 12.6%. During the follow-up period of 4059 person-years, 200 men died, yielding an incidence of mortality of 4.9 per 100 person-years. The prevalence of vitamin D deficiency was 17.5% in the deceased and 8.0% in survivors. Men who died had lower baseline 25(OH)D levels than those who survived (70.9¡22.9 vs. 77.3¡23.0 nmol/L, P=0.005), such that each SD (25nmol/L) decreased in 25(OH) D was associated with a 33% increase in the risk of mortality (RR 1.33, 95% CI: 1.12 – 1.57). Higher serum levels of PTH were associated with an increased risk of mortality (+0.5pmol/L, RR 1.16; 95% CI: 1.02-1.32). After adjusting for age and PTH, the association between 25(OH)D and mortality remained statistically significant (1.22; 1.02-1.46). Men with vitamin D deficiency and high levels of PTH were 1.63 (1.01-2.66) fold more likely to die from those with adequate vitamin D and low levels of PTH. Approximately 7% and 4% of mortality risk was attributable to vitamin D deficiency and vitamin D deficiency with high PTH, respectively.
The independent effects of vitamin D and PTH on mortality risk observed in this study suggests that men with vitamin D deficiency and hyperparathyroidism are at increased risk of all-cause mortality.