Measuring burden of unhealthy behaviours using a multivariable predictive approach: life expectancy lost in Canada attributable to smoking, alcohol, physical inactivity, and diet

Background — Behaviours such as smoking, poor diet, physical inactivity and unhealthy alcohol consumption are leading causes of death. We assessed the Canadian population burden of these behaviours by developing, validating and applying a multivariable predictive model for risk of all-cause death.

Methods — A predictive algorithm for 5-year risk of death—the Mortality Population Risk Tool (MPoRT) — was developed and validated using the 2001 to 2008 Canadian Community Health Surveys. There were approximately 1 million person-years of follow-up and 9,900 deaths in the development and validation datasets. After validation, MPoRT was used to predict future mortality and estimate the burden of smoking, alcohol, physical inactivity, and poor diet in the presence of sociodemographic and other risk factors using the 2010 national survey (approximately 90,000 respondents). Canadian period life tables were generated using predicted risk of death from MPoRT. The impact of behavioural risk factors on life expectancy was estimated using hazard ratios from the MPoRT risk model.

Findings — The MPoRT 5-year mortality risk algorithms were discriminating (C-statistic: males 0.874 [95% CI: 0.867 – 0.881]; females 0.875 [0.868 – 0.882]) and well calibrated in all 58 predefined subgroups. Discrimination was maintained or improved in the validation cohorts. For the 2010 Canadian population, men lost 6.0 years [95% CI: 5.9 to 6.2] of life expectancy due to unhealthy behaviours and women 5.7 years [95% CI: 5.5 to 5.9]. Canadians who met health behaviour recommendations had a life expectancy 17.7 years [95% CI: 17.5 to 17.9] greater than people with the least favourable risk profile (88.0 years vs. 70.3 years). Smoking, by itself, contributed 35% to 40% of the difference in life expectancy across social groups (by education achieved or neighbourhood deprivation.)

Conclusions — Multivariable predictive algorithms such as MPoRT can be used to assess health burdens for sociodemographic groups or for small changes in population exposure to risks, thereby addressing some limitations of more commonly used measurement approaches. Unhealthy behaviours have a substantial collective burden on the life expectancy of the Canadian population.