Your lungs reach their peak capacity between ages 25 and 35, after which a slow, natural decline begins. For non-smokers, this amounts to approximately 0.5% of capacity per year — a gradual reduction that is barely perceptible until later life. For smokers, this rate can be dramatically accelerated.
VO2 max — the maximum rate at which your body can use oxygen during intense exercise — is one of the strongest predictors of longevity and healthy ageing. It declines at roughly 1% per year after age 30 in sedentary individuals, but regular aerobic training can substantially slow this decline and even temporarily reverse it.
Smoking a pack a day for 10 years adds approximately 10 years to your lung age — meaning a 40-year-old 20-a-day smoker may have the lung function of a 50-year-old. NHS spirometry tests can reveal your actual lung age.
Chronic Obstructive Pulmonary Disease (COPD) affects around 1 in 13 UK adults over 35, with the majority caused by smoking. Crucially, lung damage from COPD begins years before symptoms appear — making it easy to miss until significant capacity has already been lost.