A number of researches over the years show that lung cancer is greatly linked with smoking this means that there is a close relationship between cancer and tobacco. Lung cancer deaths in the United States show that there is a drastic increase in lung cancer deaths with the increase of smoking and in recent there is a decrease in lung cancer deaths with the decrease in smoking. Similarly tobacco, diet, exercise, alcohol, tanning choices, and certain sexually transmitted diseases are the major risks for other types of cancer.
There is a correlation between cancer incidence with the lower levels of melatonin produced in the body when people spend more time in bright-light conditions. This effect is compounded in people who sleep fewer hours and in people who work at night, two groups that are known to have higher cancer rates.
Obesity increases the risk of cancer. Cancer is greatly linked with the eating habits, for example gastric cancer is more common in Japan and colon cancer is more common in the United States. Epidemiologists studying both diet and serum levels observed that high levels of beta-carotene, a precursor to vitamin A, were associated with a protective effect, reducing the risk of cancer. Effect is strong in lung cancer. Tests found no benefit of beta-carotene supplementation in reducing lung cancer incidence and mortality.