Bone Mineral Density and Parathyroid Hormone as Independent Risk Factors for Mortality in Community-Dwelling Older Adults: A Population-Based Prospective Cohort Study in Brazil. The São Paulo Ageing & Health (SPAH) Study

Abstract

Previous studies have shown a relationship between osteoporosis and increased mortality risk. However, none of these studies performed a concomitant evaluation of the parathyroid hormone (PTH)-calcium-vitamin D axis and bone mass to accurately determine the contribution of each of these parameters to survival in older subjects. Thus, we sought to investigate the association between bone parameters and mortality in a longitudinal, prospective, population-based cohort of 839 elderly subjects. Clinical data (including history of fractures and cardiovascular events) were assessed using a specific questionnaire. Laboratory exams, including serum 25OHD and PTH, were also performed. Bone mineral density (BMD) at the lumbar spine and hip were evaluated using DXA. All analyses were performed at baseline (2005 to 2007). Mortality was recorded during follow-up. Multivariate Cox proportional regression was used to compute hazard ratios for all-cause and cardiovascular mortality. Over a mean 4.06 ± 1.07 years, there were 132 (15.7%) deaths. These individuals were compared to 707 subjects who were alive at the end of the coverage period for mortality data collection. In a multivariate Cox proportional hazards model, age (HR 1.32; 95% CI, 1.13 to 1.55; p = 0.001, for each 5-year increase), male gender (HR 1.90; 95% CI, 1.30 to 2.79; p = 0.001), recurrent falls (more than two in the previous year; HR 1.65; 95% CI, 1.06 to 2.56; p = 0.026), diabetes mellitus (HR 2.17; 95% CI, 1.46 to 3.21; p < 0.001), low physical activity score (HR 1.78; 95% CI, 1.14 to 2.79; p = 0.011), prior cardiovascular event (HR 1.76; 95% CI, 1.18 to 2.63; p = 0.006), total hip BMD (HR 1.41; 95% CI, 1.15 to 1.72; p = 0.001, per each 1 SD decrease), and intact PTH (iPTH) (HR 1.06; 95% CI, 1.04 to 1.08; p < 0.001, per each 10 pg/mL increase) were independently associated with all-cause mortality. The subjects in the highest quartile of PTH (>49 pg/mL) were at a higher risk of cardiovascular death (HR 3.09; 95% CI, 1.36 to 6.99; p = 0.007) compared with the subjects in the lowest quartile (<26 pg/mL). Low BMD and higher PTH were significantly associated with mortality in community-dwelling older adults. These findings support the notion that careful screening of these bone parameters might lead to better management of older patients and improve outcomes in this population. © 2016 American Society for Bone and Mineral Research.

Keywords: BONE MINERAL DENSITY; ELDERLY; MORTALITY; PARATHYROID HORMONE; RISK FACTORS.