Smoking is the biggest risk factor for lung cancer -- and 90 percent of all lung cancer cases are related to smoking. But family history is a risk factor too and can nearly double the risk of developing the deadly disease.

A study published in the October issue of Chest found by studying a population of Japanese adults that people with a first-degree relative -- mother, father, or sibling -- who had lung cancer had a 95 percent higher risk of contracting the disease. Those who smoked had the greatest risk, but those who did not smoke were still at risk. And women were more at risk than men. The type of lung cancer most associated with family history is squamous cell carcinoma.

The results of this study do not yet translate into recommended guidelines for screening. But those with a family history of lung cancer should make their physicians aware of their history. And perhaps one day people with family history will be identified as high-risk for lung cancer and will be included in further studies. In the meantime, these individuals should avoid all contact with all inhaled and second-hand smoke and should protect their children from all forms of tobacco smoke.

The U.S. Centers for Disease Control and Prevention estimates that more than 180,000 cases of lung cancer are diagnosed each year. About 170,000 die from the disease every year. It's the second leading cause of death for men and the third leading cause of death for women.