Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD), emphysema, and cancer.
A team of British scientists headed by Richard Doll carried out a longitudinal study of 34,439 medical specialists from 1951 to 2001, generally called the "British doctors study."[24] The study demonstrated that smoking decreased life expectancy by up to 10 years and that almost half of the smokers died from diseases possibly caused by smoking (cancer, heart disease, and stroke).