Type 2 diabetes mellitus in nursing home patients: effects on bone turnover, bone mass, and fracture risk.

Abstract

Fractures are a major health burden in elderly institutionalized persons. Type 2 diabetes mellitus (DM) has a high prevalence in nursing home patients and has been associated with positive effects on bone mass in younger, community-dwelling elderly. The objective of this study was to investigate whether type 2 DM affects bone mass, bone turnover, or prospective fracture rates in frail, elderly women living in nursing homes. This study was a prospective cohort of 583 patients with type 2 DM and 1081 control (CTR) individuals above age 70 recruited from 95 nursing homes in Austria. Patients were enrolled and followed up by mobile study teams. We performed quantitative bone ultrasound measurements at the calcaneus, radius, and proximal third phalanx, measurements of quadriceps strength, and biochemical parameters of mineral metabolism and bone turnover. Patients were prospectively followed for hip and other nonvertebral fractures over 2 yr. Patients with type 2 DM had significantly higher age-, weight-, and mobility score-adjusted calcaneal stiffness (P < 0.0001), radial speed of sound (P < 0.005), and phalangeal speed of sound (P < 0.05) measurements when compared with CTRs. Mean serum PTH (-20.7%) and osteocalcin levels (-22.3%) were significantly lower (both P < 0.0001) in patients with treated type 2 DM despite comparable low serum 25-hydroxyvitamin D levels and slightly higher adjusted total serum calcium levels compared with CTRs. Important independent determinants of bone turnover in both patient groups were PTH, creatinine clearance, alanine aminotransferase, as well as glycosylated hemoglobin levels, together accounting for 30-40% of its variance. A total of 110 hip fractures occurred during the observation period, corresponding to a hip fracture rate of 3.1% (in CTRs) and 3.4% (in type 2 DM) per 100 patient years; this was not significantly different for CTRs and diabetics. Decreased PTH levels and higher levels of glycemia independently contribute to lower bone turnover in elderly nursing home patients with type 2 DM. Despite higher bone mass and lower bone turnover, hip fracture risk is comparable with women without DM.