Sunlight link to lung cancer risk

While smoking was most strongly associated with lung cancer rates, exposure to sunlight, especially ultraviolet B light, also seemed to have an impact, according to a report published in the Journal of Epidemiology and Community Health.

The researchers looked at the association between latitude, exposure to UVB light, and rates of lung cancer according to age in 111 countries across several continents.

Smoking accounted for between 75% and 85% of lung cancer cases although exposure to sunlight and UVB light, the principal source of vitamin D for the body, had an impact.

The amount of UVB light increases as you move closer to the equator and analyses showed lung cancer rates were highest in those countries furthest away from the equator and lowest in those nearest. Higher cloud cover and airborne aerosol levels were also associated with higher rates of the disease.

For men, the prevalence of smoking was associated with higher lung cancer rates, with greater exposure to UVB light associated with lower rates. Among women, cigarette smoking, total cloud cover, and airborne aerosols were associated with higher rates, and greater exposure to UVB light was associated with lower rates.

The authors of the report said: "Previous studies have found an association between UVB and lung cancer incidence in the United States.

"A survival study found that patients who had surgery for lung cancer during the summer and had the highest oral vitamin D intake, had substantially better survival than patients who had surgery during the winter and who had the lowest oral vitamin D intake."

The report believed the link between cancer and sunlight was chemically plausible, because laboratory research has shown vitamin D can halt tumour growth by promoting the factors responsible for cell death in the body.

They conclude that although cigarette smoking is the main cause of lung cancer, greater UVB exposure may reduce the incidence of the disease.