Residual confounding can occur for several reasons:
Measurement Error: Inaccuracies in measuring confounders can lead to inadequate adjustment. For example, self-reported data on physical activity or diet may not be entirely accurate. Unmeasured Confounders: Some confounding factors may not be identified or measured in the study. For example, genetic predisposition to cancer might not be accounted for in a study focusing on environmental factors. Residual Effects: Even after adjusting for confounders, there may be residual effects if the relationship between the confounder and the outcome is not linear or if the confounder is not measured precisely.
