Using device-measured physical activity data and lifetable modelling of Queensland adults aged 40+, the most active quartile could expect to live 9.7 years longer than the least active quartile. If all Queenslanders matched the most active quartile's output — roughly 85.9 additional minutes of moderate-intensity walking daily — population life expectancy at birth would reach 88.3 years, a 4.8-year gain. Step-based scenarios showed a 7.1-year gap between achieving ≥12,000 versus ≤2,000 steps/day. Crucially, each additional hour of walking was associated with approximately 177 minutes (3 hours) of life gained.
This preprint, not yet peer-reviewed, adds population-level quantification to a well-established relationship, but its lifetable design deserves scrutiny. Lifetable modelling assumes causality from observational associations — it cannot fully adjust for reverse causation, where declining health reduces activity rather than inactivity causing mortality. The use of device-measured rather than self-reported data strengthens exposure accuracy, a meaningful methodological improvement over many prior analyses. The 9.7-year gap is striking but likely reflects compounding socioeconomic, behavioural, and biological confounders beyond activity alone. For healthy adults, the 3-hours-gained-per-hour-walked metric is a compelling motivational framing, though individual returns will vary substantially by baseline fitness and age. The finding is broadly confirmatory of existing dose-response literature but strengthens the public health investment case for walkable environments and structured activity programs, particularly targeting the least active adults where marginal gains appear largest.