Additional file 1: of Does being physically active prevent future disability in older people? Attenuated effects when taking time-dependent confounders into account

Supporting information. The Supporting information provides a non-technical introduction on how marginal structural models can be estimated generically. We provide a practical demonstration of how to implement this type of modeling using standard statistical software, discussing benefits and caveats. We include an additional figure that highlights the underpinnings of time-varying treatment, time-varying confounding and the inverse probability of treatment weight. The estimation steps presented in the main manuscript are cross-referenced in the Supporting information. (DOC 1488 kb)