Healthspan
The years of life spent in good health, free of chronic disease.
Healthspan is the part of your life spent in good health and full function, as distinct from lifespan, which counts the years however they are spent. The gap between the two is the years of disability, chronic disease and dependence at the end, and in most developed countries it runs to roughly a decade.
It matters because extending lifespan without extending healthspan just lengthens that decade. The aim worth having is compression: pushing illness and frailty into as short a window as possible at the very end, rather than adding years to it.
It is harder to measure than lifespan, which is one reason it appears less often in research. Death is unambiguous and dated; good function is a judgement involving mobility, independence, cognition, freedom from disease and how someone actually feels. Studies use proxies such as disability free life expectancy, and different proxies give different answers.
The levers are the ones you would expect, and they overlap almost entirely with the lifespan levers. In a large US cohort, five low risk habits at age 50, never smoking, a healthy weight, regular activity, moderate alcohol and a good diet, were associated with roughly 12 to 14 extra years of life expectancy, and with more of those years lived free of major disease.
Strength and cardiorespiratory fitness deserve separate mention because they act on the quality of the years specifically. Sarcopenia predicts falls, fractures, hospital admissions and loss of independence, so muscle is the tissue that decides whether later decades are lived in your own home. That is a healthspan argument rather than a lifespan one.
Be sceptical of anything sold as a healthspan intervention with no outcome data. The word is doing a lot of commercial work at the moment, precisely because it is harder to measure and therefore harder to disprove.
In practice, the honest summary is dull and durable: train both strength and aerobic fitness, sleep, do not smoke, keep your waist and blood pressure in hand, and stay socially connected. Our lifestyle life expectancy tool quantifies the first version of that from the cohort data.