Osteoporosis and osteopenia in the distal forearm predict all-cause mortality independent of grip strength: 22-year follow-up in the population-based Tromsø Study

Abstract

To investigate if bone mineral density (BMD) levels of the distal forearm, consistent with osteopenia and osteoporosis, can predict mortality and if grip strength is an effect modifier. The study population constituted 6565 participants aged 50-79years at baseline in the Tromsø Study wave 4 conducted in 1994-1995. Forearm BMD measured by SXA was categorized as "normal," "osteopenia," or "osteoporosis" following WHO's definition. Cox regression with all-cause mortality as the outcome over 22years of follow-up was performed for men and women separately, adjusting for health-related factors, as well as BMD by grip strength interaction. A secondary analysis with a 15-year follow-up also adjusted for hip fractures and osteoporotic fractures. During follow-up, 3176 of participants died (47%). Those categorized as osteoporotic had higher mortality hazard ratio (HR) compared to those with normal BMD; men HR = 1.37 (95% confidence interval (CI) 1.19, 1.58) and women HR = 1.32 (1.14, 1.53) were adjusted for age, body mass index, physical activity, smoking habits, education, health status, chronic diseases, and grip strength. Corresponding HRs for osteopenia were men HR = 1.13 (1.00, 1.27) and women HR = 1.17 (1.01, 1.35). Further adjustments for fractures did only marginally attenuate the results, and HRs were still significant. There was no grip strength by BMD interaction. Men and women with low distal forearm BMD values, consistent with osteoporosis or osteopenia, had an increased mortality compared to normal BMD participants. High grip strength did not modify this association, and the association remained after adjustment for a range of health-related factors.