Early findings from the St. Louis University study were presented yesterday at the annual meeting of the American Academy of Dermatology (AAD) in Washington, D.C.
Skin cancer is the most common cancer in the U.S., with more than a million cases diagnosed each year.
"Our initial findings confirm that there is a correlation between more time spent driving and a higher incidence of left-sided skin cancers, especially on sun-exposed areas in men," St. Louis University researcher Scott Fosko, MD, says in an AAD news release.
Fosko and colleagues looked at 1,047 skin cancer patients, most of whom had nonmelanoma skin cancers.
Just over half -- 53% -- had skin cancers on the left side of their body.
The researchers focused on places likely to be exposed while driving -- the left arm, left hand, and the left side of the head and neck.
Men were particularly likely to have skin cancer in those areas.
The finding "supports the hypothesis that this may be due to UV [ultraviolet] exposure while driving," Fosko's team writes.
But the left-sided pattern wasn't seen in women.
"This gender difference may be attributed to the practice of males riding on the left side of the car more frequently," write the researchers.
The patients also completed questionnaires about their driving habits.
Results from those questionnaires weren't ready when the researchers wrote their abstract for the AAD meeting.
But in the news release, Fosko says the initial data "shows that those individuals under age 70, who consistently spent the most time per week driving a car, were more likely to develop left-sided skin cancers."
"We're also finding that all drivers who occasionally drive with the windows open had a higher incidence of left-sided skin cancers," Fosko adds.
Light skin was another skin cancer risk factor, Fosko notes.
According to the AAD, most front windshields are designed to block the sun's ultraviolet A (UVA) and ultraviolet B (UVB) rays, while side and rear windows are typically designed to block only UVB rays.
Tinting or using UV filters on auto glass may help, along with wearing broad-spectrum sunscreen and protective clothing, Fosko notes in the news release.
SOURCES: 65th annual meeting of the American Academy of Dermatology, Washington, D.C., Feb. 2-6, 2007. American Cancer Society web site: "Skin Cancer Facts." News release, American Academy of Dermatology.
By Miranda Hitti
Reviewed by Louise Chang