High prevalence of vitamin D deficiency and reduced bone mass in elderly women with Alzheimer's disease

Patients with Alzheimer's disease (AD) are at increased risk for falls and hip fractures. To better understand causes and prevention, we measured bone mineral density (BMD) in the second metacarpals of 46 ambulatory elderly w omen with AD and analyzed its relation to serum biochemical indices, sunlig ht exposure, and vitamin D intake. BMD was significantly less than in age-m atched controls. In 26% of AD patients, the serum 25-hydroxyvitamin D (25-O HD) concentration was at a deficient level (5-10 ng/mL), and in 54% it was at an osteomalacic level (<5 ng/mL), Concentrations of ionized calcium were significantly lower in patients. Conversely, concentrations of serum bone Gla-protein and urinary hydroxyproline in patients were significantly highe r than in controls. BMD correlated positively with 25-OHD concentration (p = 0.0041) and negatively with parathyroid hormone (PTH) concentration (p = 0.0022). PTH was higher in patients than in controls, and correlated negati vely with 25-OHD (p < 0.0001), Many AD patients were sunlight-deprived and consumed less than 100 IU of vitamin D per day. We concluded that vitamin D deficiency due to sunlight deprivation and malnutrition, together with com pensatory hyperparathyroidism, contributes significantly to reduced BMD in AD patients. Low BMD increases risk of hip fractures in patients with AD, b ut may be improved by vitamin D supplementation. (Bone 23:555-557; 1998) (C ) 1998 by Elsevier Science Inc, All rights reserved.