Does quitting smoking actually reverse the damage?

Substantially, and faster than most people expect. Blood pressure and heart rate begin normalising within a day. Circulation and lung function improve over weeks to months. Excess risk of coronary heart disease falls to roughly half that of a continuing smoker within a year and approaches that of a non-smoker over 10 to 15 years. Lung cancer risk falls too, though it does not return fully to baseline. Even quitting after 50 or 60 adds years of life expectancy. Combining medication with behavioural support roughly doubles success rates compared with willpower alone.