Objectives: To compare, in a large well defined sample of individuals with RA at target for a physical activity (PA) trial, those who were finally included with those who were not. Methods: 3152 individuals answered questionnaires on socio-demographic, disease-related, and psycho-social factors and PA levels. Differences between individuals making it to the baseline assessments and those who did not were analyzed in three steps. Results: In a first step, 1932 individuals were eligible for the trial as they were interested, not physically active enough, and fluent in Swedish and not participating in any other study. They were mainly female, younger, better educated, had higher income, were more likely to live with children, and had better support for exercise and higher outcome expectations on PA than the 1208 non-eligible individuals. In a second step, the 286 individuals accepting participation were better educated, had higher income, more support for exercise, less fear-avoidance beliefs and higher outcome expectations on PA than the 1646 declining participation. In a third step, the 244 individuals assessed at baseline reported less fatigue than the 42 withdrawing before assessments. Conclusions: To our knowledge, this is the first study describing the entire selection procedure from a target sample for a PA trial to the sample assessed at baseline, in individuals with RA. Factors other than those related to the disease seem to mainly determine participation and largely resemble determinants in the general population. Socio-demographic and psycho-social factors should be recognized as important for PA in people with RA.
2014. Vol. 66, no 5, 662-670 p.