Occupational activity and bone mineral density in postmenopausal women in England

Few studies have assessed the relationship between occupational activity and bone mineral density (BMD), although two case-control studies have reported a protective effect of occupational activity on hip fracture. In the present study 580 postmenopausal women aged 45-61 years completed a risk factor questionnaire including a detailed occupational history. For each job, hours spent sitting, standing, walking, lifting and carrying were recorded; these measures, evaluated at ages 20, 30, 40 years, in the current job and over the working lifetime, were used in the analysis. BMD was measured with dual-energy X-ray absorptiometry, and measurements at five sites were used in a multiple regression analysis adjusting for potential confounding variables. There was a significant negative association between sitting at age 20 years and BMD at the radius (p = 0.037), with negative relationships of borderline significance at the anteroposterior spine (p = 0.091) and whole body (p = 0.078). There were significant positive associations between standing at age 30 years and BMD at all five sites (p < 0.05), but no significant linear associations for standing at ages 20 and 40 years. No significant associations were found for lifetime or current occupational measures of sitting, standing, walking and lifting or carrying. The lack of consistency of these significant findings suggests that they may have occurred by chance, and that occupational activity has little if any effect on BMD in postmenopausal women.