Associations between grip strength change and axial postmenopausal bone loss--a 10-year population-based follow-up study.

The aim of the present study was to investigate the associations between grip strength change and postmenopausal bone loss. The study population, 622 peri- and postmenopausal women, was a random sample of the OSTPRE-study cohort (n=13,100) in Kuopio, Finland. Bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN) was measured with dual X-ray absorptiometry and grip strength with a pneumatic squeeze dynamometer at baseline in 1989-1991, at the 5-year follow-up in 1994-1997 and at the 10-year follow-up in 1999-2001. Women were divided into three groups according to the change in age-grouped grip strength quartile they belonged to in each measurement (n in 5-year/10-year follow-up): "decreased" (n=150/n=140), "maintained" (n=314/n=320) and "improved" (n=158/n=162). Women within the improved group had significantly lower bone loss at both FN and LS in comparison to the other two groups after 10 years of follow-up (P<0.01). Furthermore, in HRT non-users (n=305) the difference between the improved group and maintained group was only modest (P=0.04). In contrast, in HRT users (n=310) the mean annual BMD change among the improved group was positive (bone gain 0.11%/year) and differed significantly in comparison to modest bone loss in the decreased and maintained groups in both LS and FN (P<0.01). The linear trend between grip strength quartile change and LS/FN bone loss was significant in HRT users (P<0.001) in contrast to HRT non-users (P=NS) in the linear regression model. Any of these differences were not affected by adjustments for age, weight, height and other potential confounders. In conclusion, the present study suggests that improvement in age-grouped grip strength quartile is strongly associated with axial bone loss among postmenopausal women. This effect seemed to interact positively with estrogen repletion status. These results encourage performing further clinical studies on associations between muscle strength changes and bone loss.