Peripheral body fat has a protective role on bone mineral density in elderly women

Abstract

Objectives: To determine whether bone mineral density is lower in women living in homes for the elderly as compared to free dwelling control subjects, and to investigate factors affecting possible differences. This is the first study with this objective as the primary aim.

Design: Case-control study.

Subjects and methods: Institutionalised independent elderly women (n=22, mean age=75.1 y±6.43 s.d.) randomly selected in a home for the elderly and 22 age-matched control women randomly selected from a sample representative of the independent non institutionalised local population who underwent dual energy X-ray absorptiometry (DXA) at the lumbar spine and right femoral neck; anthropometric measurements (height, weight, subscapular and triceps skinfold thickness); general questionnaire.

Results: Mean bone mineral density at the femoral neck was 0.618 g/cm² (±0.130 s.d.) in institutionalised women and 0.709 g/cm² (±0.106 s.d.) in controls (P=0.02, t-test). Controlling for confounding factors in the analysis of covariance, triceps skinfold thickness and living in a home for the elderly turned out to be significant determinants of bone mineral density.

Conclusion: When compared to free dwelling control subjects, institutionalised women show lower bone density, that is the main risk factor for fracture. Reduced peripheral body fat was significantly associated with the low bone mineral density observed. Health programs aimed at decreasing the incidence of fractures among institutionalised subjects will also have to consider the effect of nutritional or life style factors that reduce peripheral body fat.