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.[1] 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 (one in a million probability of death) the microlife is intended for "rough but fair comparisons between the sizes of chronic risks".[2] 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.
"A daily loss or gain of 30 minutes can be termed a microlife, because 1 000 000 half hours (57 years) roughly corresponds to a lifetime of adult exposure."
The microlife exploits the fact that for small hazard ratios the change in life expectancy is roughly linear.[3] 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.May 2014.
| Men | Women | ||
| Smoking | |||
| Smoking 15 - 24 cigarettes | -10 | -9 | |
| Alcohol intake | |||
| First drink (of 10 g alcohol) | 1 | 1 | |
| Each subsequent drink (up to 6) | -½ | -1 | |
| Obesity | |||
| Per 5 units above body mass index of 22.5 each day | -3 | -3 | |
| Per 5 kg above optimum weight for average height each day | -1 | -1 | |
| Sedentary behaviour | |||
| 2 hours watching television | -1 | -1 | |
| Diet | |||
| Red meat, 1 portion (85 g, 3 oz) | -1 | -1 | |
| Fruit and vegetable intake, =5 servings (blood vitamin C >50 nmol/L) | 4 | 3 | |
| Coffee intake | |||
| 2-3 cups | 1 | 1 | |
| Physical activity | |||
| 2 | 2 | ||
| Subsequent 40 minutes of moderate exercise | 1 | ½ | |
| Statins | |||
| 1 | 1 | ||
| Air pollution | |||
| -½ | -½ | ||
| Geography | |||
| Per day being a resident of Russia v Sweden | -21 | -9 | |
| Era | |||
| Per day living in 2010 v 1910 | 15 | 15 | |
| Per day living in 2010 v 1980 | 8 | 5 | |