This assessment of epidemiological data shows that the gain in life expectancy that accompanies a healthy lifestyle is much the same whether or not an individual suffers from multiple age-related conditions. As always in this sort of study, the question is the degree to which this reflects the point that the onset of more serious conditions renders people less able to be active, versus a matter of good lifestyle choices producing corresponding benefits over time. Animal studies make it quite clear that efforts to maintain good health do in fact make a real difference over the long term, but that sort of certainty is hard to extract from human epidemiological data. That said, the most relevant factors, such as smoking and diet, are much less impacted by disease status than is the case for physical activity.

Whether a healthy lifestyle impacts longevity in the presence of multimorbidity is unclear. We investigated the associations between healthy lifestyle and life expectancy in people with and without multimorbidity. A total of 480,940 middle-aged adults (median age of 58 years, 46% male, 95% white) were analysed in the UK Biobank; this longitudinal study collected data between 2006 and 2010, and participants were followed up until 2016. We extracted 36 chronic conditions and defined multimorbidity as 2 or more conditions. Four lifestyle factors, based on national guidelines, were used: leisure-time physical activity, smoking, diet, and alcohol consumption. A combined weighted score was developed and grouped participants into 4 categories: very unhealthy, unhealthy, healthy, and very healthy. Survival models were applied to predict life expectancy, adjusting for ethnicity, working status, deprivation, body mass index, and sedentary time.

A total of 93,746 (19.5%) participants had multimorbidity. During a mean follow-up of 7 (range 2-9) years, 11,006 deaths occurred. At 45 years, in men with multimorbidity an unhealthy score was associated with a gain of 1.5 additional life years compared to very unhealthy score, though the association was not significant, whilst a healthy score was significantly associated with a gain of 4.5 life years and a very healthy score with 6.3 years. Corresponding estimates in women were 3.5, 6.4, and 7.6 years. Results were consistent in those without multimorbidity and in several sensitivity analyses. For individual lifestyle factors, no current smoking was associated with the largest survival benefit.

In conclusion, we found that regardless of the presence of multimorbidity, engaging in a healthier lifestyle was associated with up to 6.3 years longer life for men and 7.6 years for women; however, not all lifestyle risk factors equally correlated with life expectancy, with smoking being significantly worse than others.