Assessment of Activity Profiles in Older Adults and Lower Limb Bone Parameters: Observations from the Hertfordshire Cohort Study

Abstract

As muscle strength and function decline with age the optimal high-impact physical activity (PA) required for bone remodelling is rarely achievable in older adults. This study aimed to explore the activity profiles of community-dwelling older men and women and to assess the relationship between individual PA profiles and lower limb bone parameters. Participants from the Hertfordshire Cohort Study wore triaxial accelerometers for 7 days and counts of low (0.5–1.0 g), medium (1.0–1.5 g), and high (> 1.5 g) vertical-impact activity were calculated. Two years later, participants underwent a pQCT scan of the tibia (4% and 38% sites) to obtain measures of bone mineral density and bone geometry. Linear regression was used to quantify associations between bone and PA loading profiles adjusting for age, sex, loading category, and BMI. Results are presented as β [95% confidence interval]. Bone and PA data were available for 82 participants. The mean (SD) age at follow-up was 81.4(2.7) years, 41.5% (n = 34) were women. The median low-impact PA count was 5281 (Inter-quartile range (IQR) 2516–12,977), compared with a median of only 189 (IQR 54–593) in medium, and 39 (IQR 9–105) in high-impact counts. Positive associations between high-impact PA and cortical area (mm2), polar SSI (mm3), and total area (mm2) at the 38% slice (6.21 [0.88, 11.54]; 61.94 [25.73, 98.14]; 10.09 [3.18, 16.99], respectively). No significant associations were found at distal tibia. These data suggest that maintaining high (> 1.5 g)-impact activity is difficult for older adults to achieve; however, even small amounts of high-impact PA are positively associated with selected cortical bone parameters 2 years later.

Is There a Causal Relationship between Physical Activity and Bone Microarchitecture? A Study of Adult Female Twin Pairs

“…[ 37 ] A third cohort study reported increased cortical area and total area at the tibial shaft with high‐impact PA in women and men with a mean age of 81 years, while there were no changes in the bone structure of the distal tibia. [ 35 ] The discrepancy between the results of these studies may be due to differences in study design, sample size, and responses of the tibia site that was measured, which depends on the type of activity. The tibial shaft contains almost exclusively cortical bone and a thick cortex, while the distal tibia contains mainly trabecular bone and a thin cortex.…”

“…[ 34 ] In studies where pQCT images were obtained of both the tibial shaft and the distal tibia, the results were ambiguous. [ 35 , 36 , 37 ] From a cross‐sectional study that compared twins who were discordant for leisure time PA during the last 30 years, active twins had larger cortical CSA, thicker cortices, and higher trabecular vBMD at the tibial shaft than their inactive co‐twin. [ 36 ] Another cross‐sectional study reported increased cortical thickness and higher total BMC at the tibial shaft with moderate to vigorous activity in older adults.…”