In this study, we investigated if the association between aging and physical inactivity was different between men and women and between primary and secondary prevention patients. We performed a cross-sectional analysis of three primary care samples including primary and/or secondary prevention patients (total n = 4726). The raw data of the samples are attached. Baseline data for sample 1 were collected in the years 2013–14, for sample 2 in 2009–10 and for sample 3 in 2009. Activity levels were measured by the patient reported Rapid Assessment of Physical Activity questionnaire. A multilevel regression analysis was used to explore the association between aging and physical inactivity, adjusted for confounders. We examined potential effect modification by gender and the presence of CVD on the association between aging and physical inactivity. In the READ_ME_FIRST file we summarized the Methods section as well as the best fitting model that we used for the analysis. Moreover, we added the full text_paper.