A smoker's risk of lung cancer may be linked to when they light their first cigarette of the day.
Researchers looked at survey data from current and former smokers in the U.S. and Italy.
The survey included questions about how soon smokers had their first cigarette after waking.
Those who waited at least one hour to smoke were significantly less likely to develop lung cancer than those who began earlier.
The link was stronger among current smokers and lighter smokers.