microlife

{{Short description|Unit of risk – half an hour of life expectancy}}

{{for|the manufacturer of medical devices|Microlife Corporation}}

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.{{Cite journal|author=Lin, Chia-Yu, Gelman, Andrew, Price, Phillip N., and Krantz, David H.|date=1999|title=Analysis of Local Decisions Using Hierarchical Modeling, Applied to Home Radon Measurement and Remediation|journal=Statistical Science|volume=14|url=http://www.stat.columbia.edu/~gelman/research/published/lin.pdf|pages=305–337}} 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".{{cite journal |last=Spiegelhalter |first=D. |title=Using speed of ageing and "microlives" to communicate the effects of lifetime habits and environment |journal=BMJ |volume=345 |issue=dec14 14 |date=2012-12-14 |issn=1756-1833 |doi=10.1136/bmj.e8223 |pages=e8223|pmid=23247978 |s2cid=27745393 |url=http://www.bmj.com/content/bmj/345/bmj.e8676.full.pdf }} 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.{{cite journal |last=Haybittle |first=J. |title=The use of the Gompertz function to relate changes in life expectancy to the standardized mortality ratio |journal=International Journal of Epidemiology |publisher=Oxford University Press (OUP) |volume=27 |issue=5 |date=1998-10-01 |issn=1464-3685 |doi=10.1093/ije/27.5.885 |pages=885–889|pmid=9839748 |doi-access=free }} 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.{{cite needed|date=May 2014}}

File:Microlife effort.png

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class="wikitable" |+ Microlives gained/lost per day of exposure, based on estimated life expectancy effects of long term lifestyle and demographic risk factors, for men and women aged 35 years. !Risk factor	Men	Women
colspan="3"|Smoking
style="padding-left:1em;"|Smoking 15–24 cigarettes	−10	−9
colspan="3"|Alcohol intake
style="padding-left:1em;"|First drink (of 10 g alcohol)	1{{Dubious|date=June 2023}}	1
style="padding-left:1em;"|Each subsequent drink (up to 6)	−½	−1
colspan="3"|Obesity
style="padding-left:1em;"|Per 5 units above body mass index of 22.5 each day	−3	−3
style="padding-left:1em;"|Per 5 kg above optimum weight for average height each day	−1	−1
colspan="3"|Sedentary behaviour
style="padding-left:1em;"|2 hours watching television	−1	−1
colspan="3"|Diet
style="padding-left:1em;"|Red meat, 1 portion (85 g, 3 oz)	−1	−1
style="padding-left:1em;"|Fruit and vegetable intake, =5 servings (blood vitamin C >50 nmol/L)	4	3
colspan="3"|Coffee intake
style="padding-left:1em;"|2-3 cups	1	1
colspan="3"|Physical activity
style="padding-left:1em;"|First 20 minutes of moderate exercise	2	2
style="padding-left:1em;"|Subsequent 40 minutes of moderate exercise	1	½
colspan="3"|Statins
style="padding-left:1em;"|Taking a statin	1	1
colspan="3"|Air pollution
style="padding-left:1em;"|Per day living in Mexico City v London	−½	−½
colspan="3"|Geography
style="padding-left:1em;"|Per day being a resident of Russia v Sweden	−21	−9
colspan="3"|Era
style="padding-left:1em;"|Per day living in 2010 v 1910	15	15
style="padding-left:1em;"|Per day living in 2010 v 1980	8	5