Does reducing the number of cigarettes smoked per day but not stopping lower your risk of health hazards?
A study from Norway showed that there is no reduction in premature death in patients who significantly reduced but did not quit smoking. By contrast, quitting entirely, at any age, significantly increases life expectancy.
Source: Tverdal, A., & Bjartveit, K. (2006). Health consequences of reduced daily cigarette consumption. Tobacco Control, 15(6), 472-480.