Risks vary according to the amount of tobacco smoked, with those who smoke more at greater risk.Smoking so-called "light" cigarettes does not reduce the risk.Smoking most commonly leads to diseases affecting the heart and lungs and will most commonly affect areas such as hands or feet with first signs of smoking related health issues showing up as numbness, with smoking being a major risk factor for heart attacks, chronic obstructive pulmonary disease (COPD), emphysema, and cancer, particularly lung cancer, cancers of the larynx and mouth, and pancreatic cancer.
Additionally, smoke-free laws that ban smoking in public places such as workplaces, theaters, and bars and restaurants reduce exposure to secondhand smoke and help some people who smoke to quit, without negative economic effects on restaurants or bars.
From the 1890s onwards, associations of tobacco use with cancers and vascular disease were regularly reported; a metaanalysis citing 167 other works was published in 1930, and concluded that tobacco use caused cancer.
Starting smoking earlier in life and smoking cigarettes higher in tar increases the risk of these diseases.
Also, environmental tobacco smoke, or secondhand smoke, has been shown to cause adverse health effects in people of all ages.
A year after quitting, the risk of contracting heart disease is half that of a continuing smoker.
The health risks of smoking are not uniform across all smokers.
A person's increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked.
However, if someone stops smoking, then these chances gradually decrease as the damage to their body is repaired.
Cigarettes sold in underdeveloped countries tend to have higher tar content, and are less likely to be filtered, potentially increasing vulnerability to tobacco smoking related disease in these regions.
Similarly, the United States Centers for Disease Control and Prevention describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide." According to a 2014 review in the New England Journal of Medicine, tobacco will, if current smoking patterns persist, kill about 1 billion people in the 21st century, half of them before the age of 70.