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Highlights • Osteodynapenia but not osteosarcopenia increased the risk of fracture. • Osteodynapenia did not lead to a significantly greater fracture risk compared to having osteopenia or dynapenia alone. • Osteosarcopenia but not osteodynapenia increased the risk of mortality. • Osteosarcopenia did not lead to a significantly greater mortality risk compared to having osteopenia or sacropenia alone. Abstract Aim: To determine whether older adults with low muscle mass (sarcopenia) and strength (dynapenia), in the presence of osteoporosis/osteopenia, have an increased risk of fracture and mortality over 10 years, compared to those with low muscle or low bone mass alone or with neither condition. Methods: 1032 participants (52% women; mean age 62.9 ± 7.4 years) were prospectively followed for 10 years. Mortality was ascertained from the death registry and fractures were self-reported. Baseline appendicular lean mass (ALM) was assessed using dual-energy X-ray absorptiometry and normalised to body mass index (BMI). Hand grip strength (HGS) was assessed by dynamometer. Osteosarcopenia and osteodynapenia were defined as having T-scores of the total hip and/or lumbar spine bone mineral density (BMD) < –1 combined with being in the lowest 20% of the sex-specific distribution for ALM/BMI or HGS respectively. Results: Incident fracture risk was significantly higher in participants who were osteodynapenic (RR = 2.07, 95% CI: 1.26–3.39), dynapenic alone (RR = 1.74, 95% CI: 1.05–2.87), and osteopenic alone (RR = 1.63, 95% CI: 1.15–2.31), compared to those without dynapenia or osteopenia. Mortality risk was significantly higher only in participants with osteosarcopenia (RR = 1.49, 95% CI: 1.01–2.21) compared to those without sarcopenia or osteopenia. However, osteosarcopenia and osteodynapenia did not lead to a significantly greater fracture or mortality risk compared to having these conditions on their own. Conclusion: These findings suggest that the combined effect of osteopenia and sarcopenia or dynapenia on fracture and mortality risk, respectively, may not be greater than that of each individual condition. [ABSTRACT FROM AUTHOR]

• In addition to inter-individual differences, intra-individual variability in physical activity is associated with knee pain and functional limitation. • When participants engaged in more physical activity than their average level, they had lower knee pain and functional limitation. • Conversely, having higher functional limitations compared with an individual's average was associated with lower levels of physical activity. To describe the associations between interindividual (between-person) and intraindividual (within-person) variability in physical activity (PA) and knee pain and functional limitation among older adults. We also investigated the potential bidirectional association of between-person and within-person variability in knee pain and functional limitation with PA. Participants (N = 1064; 51% women; mean age 63 ± 7.4 years) were measured at baseline, 2.5, and 5 years. PA was measured using pedometers. Knee pain and functional limitation were assessed using the WOMAC scale. A two-part hurdle model, with adjustment for confounders, estimated the association of between-person and within-person variability in PA with knee pain/functional limitation (as the outcome). Linear mixed effect regression models described the association of between-person and within-person variability in knee pain and functional limitation with PA (as the outcome). Between-person effects showed that participants with a higher 5-year average PA had lower average WOMAC scores (β= –1.17, 95% CI: –1.82, –0.51). Within-person effects showed that at time-points when participants had a higher PA level than average, they also had lower WOMAC scores (β= –0.85, 95% CI: –1.36, –0.35). Conversely, both between-person (β= –15.6, 95% CI: –22.5, –8.8) and within-person increase (β= –7.4, 95% CI: –13.5, –1.4) in WOMAC scores were associated with lower PA. These findings suggest that PA and knee pain/dysfunctional contribute to the development of one another. Pain can lead to changes in inter- and intraindividual PA levels, but the reverse is also possible – changes in PA results in changes in inter- and intraindividual pain/dysfunctional levels. [ABSTRACT FROM AUTHOR]