Xuxi Zhang

condition by adding it to the regression models as a covariate. We also repeated the analyses for the control group only and found similar results. Additionally, we considered the results of those persons who had received specific UHCE interventions may have had an effect on the changes in the frequency of PA. Therefore, we conducted a sensitivity analysis to control for specific UHCE interventions that may promote PA. For this purpose, the intervention condition in the multivariable regression model was categorized into three categories instead of two: (1) control group, (2) intervention promoting PA group (participants who enrolled in the falls and/or frailty pathway, and (3) intervention not promoting PA group (participants who did not enroll in the falls and/or frailty pathway). The results of this sensitivity analysis were similar to our primary findings. Fifth, our observational study cannot confirm causality between PA and frailty. A decrease in frequency of PA might be the cause of the progression of frailty, or simply the epiphenomenon of a declining health status. In addition, a decrease in PA might also have been caused by external factors leading to frailty, such as an accident, stroke or fall during the year. Adjusting for multi ‐ morbidity at baseline, only partly reflects these variations of PA during 12 ‐ month follow ‐ up. Sixth, over adjustment bias may exist because we adjusted for many covariates and some of these (e.g. multi ‐ morbidity) may act partially as a confounder and partially as a mediator. Last, there may be overlap between PA and two items of the TFI (walking and balance) which could cause over ‐ estimation of the association. However, when we explored the association between PA and overall frailty, after deleting these two items the results were similar. Hence, we do not expect that this limitation has changed our findings. CONCLUSIONS In conclusion, we found that both maintaining a regular frequency of PA and increasing to a regular frequency of PA are associated with maintaining or improving the level of frailty among European community ‐ dwelling older adults older than 70 years, not only in the physical domain, but also in the psychological and social domains of frailty. Our findings support the development of new public health strategies to encourage adults older than 70 years to maintain a regular frequency of PA to prevent and delay not only physical but also psychological and social frailty. More RCTs studying the effect of the frequency and intensity levels of PA are needed to determine the optimum level of PA required to prevent the progression of physical, psychological and social frailty among older adults. 64 Chapter 3