Life-expectancy
methods.
These research comparisons are separate from the eight-habit checklist and from the guide’s original content library.
Study groups, not your predicted years.
These numbers were not calculated from your answers. These are modelled differences between study groups, not years added to your life. The study does not predict your lifespan or prove that changing a habit will cause the same gain. Your checklist score is separate. Not medical advice.
Li et al. (2018) compared groups from two US health-professional cohorts. Their four-factor sensitivity analysis excluded alcohol. The comparison included never smoking, lower-risk BMI, physical activity and diet.
Women · starting at age 50
11.4 years
Modelled remaining-life-expectancy difference: all four lower-risk factors versus none.
95% group confidence interval: 9.5–13.3 years.
Men · starting at age 50
10.0 years
Modelled remaining-life-expectancy difference: all four lower-risk factors versus none.
95% group confidence interval: 9.2–10.9 years.
A personal estimate is not available for your age group with this model. A group confidence interval is not a personal prediction interval. You do not need to provide your age or sex to read either comparison.
Li et al., Circulation 2018 · Supplement, eFigure 7 · Life-expectancy methods and limitations
What was studied?
Li Y, Pan A, Wang DD, et al. Impact of Healthy Lifestyle Factors on Life Expectancies in the US Population. Circulation. 2018;138:345–355. DOI: 10.1161/CIRCULATIONAHA.117.032047.
The study followed 78,865 women in the Nurses’ Health Study and 44,354 men in the Health Professionals Follow-up Study. Life-table modelling began at age 50. These US health-professional cohorts are not a representative sample of every country, age or occupation.
The original five-factor comparison included alcohol. We display the published four-factor sensitivity analysis that excludes alcohol, rather than subtracting a guessed alcohol benefit from the original result. We do not suggest starting to drink.
Research factors are not these eight questions
The study used its own definitions: never smoking, BMI 18.5–24.9, at least 30 minutes per day of moderate-to-vigorous physical activity, and diet in the top 40% of the cohort’s Alternative Healthy Eating Index. The original analysis considered BMI history and detailed repeated measurements. One fruit-and-vegetable question does not reproduce this diet index, and one strength session does not reproduce the activity threshold.
Our checklist also includes a seat belt and email security. It contains no smoking, alcohol, BMI, diagnosis or psychological screening questions. No checklist answer or score is used to calculate years, and no per-habit years are assigned.
What the interval means
The 95% confidence intervals describe statistical uncertainty in the modelled group difference. They do not describe the range of years any particular person will gain. Unmeasured differences, future behavior, illness, countries and calendar periods can affect applicability. Observational associations do not prove an intervention would cause the same gain.
Why there is no personal estimate
A personal estimate is not available for your age group with this model. We have not built or validated an individual lifespan model for this website. We do not extrapolate these age-50 group results to young adults or use visitors’ average scores as a population baseline.
Read the full paper · Read the supplementary material (eFigure 7)
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