A microlife is a unit of risk representing half an hour change of life expectancy.[1]
Discussed by David Spiegelhalter and Alejandro Leiva, and also used by Lin et al.[2] 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".[1] 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.[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.[citation needed]
Risk factor | Men | Women |
---|---|---|
Smoking | ||
Smoking 15–24 cigarettes | −10 | −9 |
Alcohol intake | ||
First drink (of 10 g alcohol) | 1[dubious – discuss] | 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 | ||
First 20 minutes of moderate exercise | 2 | 2 |
Subsequent 40 minutes of moderate exercise | 1 | ½ |
Statins | ||
Taking a statin | 1 | 1 |
Air pollution | ||
Per day living in Mexico City v London | −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 |
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