People with low bone mineral density (BMD) are at increased risk of developing Alzheimer’s disease, researchers report. Low BMD is also associated with all-cause dementia in women, but not men.

“Some, but not all studies have suggested that estrogen replacement therapy has a beneficial effect on cognition in postmenopausal women,” Dr. Zaldy Sy Tan, of Beth Israel Deaconess Medical Center, Boston, and colleagues write in the Archives of Neurology. “BMD is a potential surrogate marker for cumulative estrogen exposure.”

In a community-based study, the researchers examined whether low BMD in almost 1000 mentally intact elderly patients increased their risk of Alzheimer’s. The subjects had bone density measured at several places in their body between 1988 and 1989.

During 8 years of follow-up, 95 participants developed dementia. Of these, 75 were classified as having Alzheimer’s disease.

Overall, 35 of the 243 patients in the lowest category of hipbone density developed dementia, classified as Alzheimer’s in 27.

After adjusting for age, smoking, estrogen use, sex, stroke, education and other factors, women with the lowest BMD had twice the risk of developing Alzheimer’s disease and dementia, the researchers found.

These findings, Tan’s group concludes, suggest that women with low BMD “may benefit from estrogen replacement therapy” - despite the well-known increased risk of other complications.

SOURCE: Archives of Neurology, January 2005.