Time Dependent Relative Risks in Life Insurance Medical Underwriting

Introduction .- Life insurance medicine focuses on mortality hazards in specified periods. People are free to insure their lives for shorter or longer terms. Because the chosen terms range from 1 year to a life time, life insurers have to take into account the fact that the predictive value of risk indicators can and will change over time. The time a risk indicator keeps its predictive value, will be dependent on its biological effects, volatility, and treatability. For a given applicant this implies that the relative hazard (RH) calculated for his/her medical condition should be dependent on the term of the insurance. The main objective of this study is to determine if some commonly used risk indicators - previously used to study age dependency of relative risks - have a predictive value that increases with the observation period. (1) Methods .- This population-based cohort study uses NHANES-data files from the Third National Health and Nutrition Examination Survey (NHANES III) and the NHANES Linked Mortality Files 2010. Only participants aged 20 to 69 that were examined in mobile examination centers, without a history of some prevalent high risk diseases were included. The observed mortality was compared to the expected mortality in a Generalized Linear Model (GLM) with Poisson error structure with two reference populations, which both can serve as preferred reference for life insurers: The United States Life Tables 2008 (USLT) and the 2008 Valuation Basic Tables (VBT) based on the insured population of 35 US Life insurers. The time dependency of the RHs of the systolic blood pressure (SBP), aspartate aminotransferase (ASAT), lactate dehydrogenase (LDH), serum albumin and albuminuria, was assessed, with correction for ethnicity, household income, history of diabetes mellitus, BMI and serum cholesterol. To be able to compare the results with the results of the Age Dependency Study (ADS), the same data, risk indicators, statistical analysis method, and the Generalized Linear Model (GLM) were used. Results .- Contrary to the results in the univariate analyses, the multivariate analyses show no difference between the USLT and VBT models. In both models the RHs of SBP and albuminuria increase over time, while the RH of LDH decreases over time. Only the slopes are different, reflecting the rate of mortality increase between USLT and VBT. The RHs of ASAT and serum albumin are independent of time in both models. Discussion .- Time dependency of RHs can be assumed to exist with many risk indicators. Time dependency may take two forms: decreasing the RH and increasing the RH of a variable as time passes. Medical underwriting guidelines should therefore differentiate between short term and long term life insurances. Medical directors should realize that the presence of time dependency diminishes the value of short term clinical studies for life insurance medical underwriting. Life insurance mortality studies should always contain a discussion of the time dependency of the predictive value of the variables under study.