Subjective and Objective Assessment of Physical Activity in Older Adults: Results from Berlin Aging Study II

Physical activity has a substantial impact on health and mortality. Besides questionnaires that rely on subjective assessment of activity levels, accelerometers can help to objectify an individuals physical activity. Physical activity was assessed with the GT3X activity monitor (ActiGraph LLC, USA) in 797 participants of the Berlin Aging Study II (BASE-II) and compared with questionnaire data obtained from the Rapid Assessment of Physical Activity (RAPA). Of all participants, 760 fulfilled the wear-time based inclusion criteria. Mean age was 75.6 years (SD: 3.8 years, range 66.0 - 94.1 years) and 53% of the included participants were female. Average wear time was 23.2 hours/day (SD 1.3 hours/day). Statistically significant differences between RAPA groups were found for all accelerometric variables except energy expenditure. Post-hoc analysis, however, suggested low agreement between subjective and objective assessment of physical activity. When focusing on the first question of the RAPA questionnaire, participants who reported to be "seldom or never active" showed statistically significant lower activity levels in Vector Magnitude, step counts, and cut-off defined moderate physical activity (p<0.05). Total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides, fasting glucose and hemoglobin A1c were weakly correlated with accelerometric variables (Pearsons r [&le;] 0.25). Results from this study suggest that subjectively assessed data from the RAPA and objectively assessed data from accelerometric variables obtained from the GT3X monitor are partially inconsistent in terms of the physical activity level of the participants.