20 | Chapter 2 The aims of this study were to investigate the associations between physical activity and falls, and physical activity and fall-related fractures, and to examine whether frailty is an effect modifier of both associations in a population of older adults. Since physical activity helps to maintain balance control and muscle and bone strength, but leads to increased exposure to situations where falls occur, physical activity was expected to increase fall incidence among both non-frail older adults and frail older adults (72-74). The fracture risk was expected to decrease among non-frail, but to increase in frail older adults with increased duration of physical activity (74). METHODS Study design and participants This study was performed using data from the Longitudinal Aging Study Amsterdam (LASA), an ongoing cohort study on physical, cognitive, emotional and social functioning in older adults to determine predictors and consequences of ageing (93). The data collection procedures have been described in detail elsewhere (94, 95). For the current study, data were used from the LASA 75 PLUS study, i.e. five measurement waves over a period of three years (time point 1, T1: baseline, 2015/2016, time point 2, T2: nine months after baseline, time point 3, T3: 18 months after baseline, time point 4, T4: 27 months after baseline and time point 5, T5: 3 years after baseline, 2018/2019) (96). A total of 601 participants agreed to participate. Because of missing accelerometry data and data of the LASA Physical Activity Questionnaire, final analysis in this longitudinal study included a representative study population of 311 participants aged 75 years or older with complete data. The Medical Ethics Committee of the VU University Medical Centre approved the study. All participants in this study signed informed consent. This study was conducted according to the principles of the Declaration of Helsinki (7th revision, October 2013) and is performed in accordance with the Medical Research Involving Human Subjects Act (WMO) and other guidelines, regulations and acts such as Good Clinical Practice and the statement conducting research involving humans. Baseline characteristics At T1, information was collected about the age, sex, and BMI of the participants. Moreover, dizziness complaints were determined by the question whether participants are dizzy regularly (yes/no). Furthermore, the six-meter walking time was assessed by asking subjects to walk three meters, to turn around and walk back three meters as quickly as possible. Based on this assessment, an average walking speed was calculated. Last, grip strength was determined by using a grip strength dynamometer (JAMAR 5030J1 Hydraulic Hand Dynamometer).
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