Reverse Causation and Illness-related Weight Loss in Observational Studies of Body Weight and Mortality

Authors:Flegal, K. M., Graubard, B. I., Williamson, D. F. and Cooper, R. S.
"In studies of weight and mortality, the construct of reverse causation has come to be used to imply that the exposure-outcome relation is biased by weight loss due to preexisting illness. Observed weight-mortality associations are sometimes thought to result from this bias. Evidence for the occurrence of such bias is weak and inconsistent, suggesting that either the analytical methods used have been inadequate or else illness-related weight loss is not an important source of bias."