This study assesses the effect of changes observed on population level data for major critical illness conditions on current and future expected claim rates. Main focus is identifying the underlying reasons for changes seen in the past to distinguish between once-off effects and those that can reasonably be expected to continue. Adjustments are made to allow for differences between trends in insured lives and the general population. Developments on the horizon that could affect future claim rates are also considered. As examples of the work done this paper discusses trends for heart attacks and the effect of screening for cancer.