2 Physical activity as a risk or protective factor | 31 Sensitivity analyses LASA Physical Activity Questionnaire As a sensitivity analysis, the LASA Physical Activity Questionnaire (LAPAQ) was used to define physical activity. This sensitivity analysis was performed in 505 participants, and thus had a larger power compared to the primary analysis. Age, physical activity and frailty were comparable to the study population of the primary analysis. Results were similar to the primary analysis (Appendix 2.1, Table A2.1.1 and A2.1.2). Larger study population In a second sensitivity analysis, the primary analysis was repeated in a larger study population of 1,002 participants of 65 years or older to further increase the power of the analyses. This sensitivity analysis was conducted in a larger study population to evaluate the robustness of the study results. The mean amount of physical activity was 88.4 minutes per day. Frailty index scores were similar compared to the study population of the primary analysis. Results were similar to the primary analysis (Appendix 2.1, Table A2.1.3 and A2.1.4). DISCUSSION This is the first study that examined the moderating role of frailty in the association between physical activity and falls, and physical activity and fractures among community-dwelling older adults. We hypothesized to find a paradox in that PA would have a different relation with falls or fractures in frail compared to non-frail older adults, but in fact, we did not find a relation between PA and either falls nor fractures. Moreover, frailty did not modify both associations, but was associated with an increased fall and fracture risk. Sensitivity analyses in a larger study population found comparable results and thus substantiated the results of the primary analysis. Therefore, we cannot confirm our hypothesis that physical activity is a risk factor for falls in all older adults and fractures in frail older adults, and is protective for fractures in non-frail older adults. In contrast to our results, an association between physical activity and fall risk was previously found and showed that physical activity can both increase and decrease fall risk (75, 76, 78, 109). An explanation for not finding an association between physical activity and fall risk is that physical activity levels of our participants showed little variance. Therefore, participants with the highest and lowest physical activity levels were possibly underrepresented, causing an underestimation of the association between physical activity and falls. Another possible explanation is that some studies reported that men have an increased fall risk and women a decreased fall risk when being more physically active (70, 110). However, when we added
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