Microlife


A microlife is a unit of risk representing half an hour change of life expectancy.
Discussed by David Spiegelhalter and Alejandro Leiva, and also used by Lin et al. for decision analysis, microlives are intended as a simple way of communicating the impact of a lifestyle or environmental risk factor, based on the associated daily proportional effect on expected length of life. Similar to the micromort the microlife is intended for "rough but fair comparisons between the sizes of chronic risks". This is to avoid the biasing effects of describing risks in relative hazard ratios, converting them into somewhat tangible units. Similarly they bring long-term future risks into the here-and-now as a gain or loss of time.
The microlife exploits the fact that for small hazard ratios the change in life expectancy is roughly linear. They are by necessity rough estimates, based on averages over population and lifetime. Effects of individual variability, short-term or changing habits, and causal factors are not taken into account.