Poor weather linked to prostate cancer

Grim weather up North may be making men more prone to prostate cancer, new research suggests.

Scientists believe a combination of cold temperatures and lack of sun could help explain higher rates of the disease in northerly parts of the world.

Poor exposure to the sun's rays can lead to vitamin D deficiency, which may increase prostate cancer risk, it is claimed.

At the same time, cold weather might help to slow the degradation of cancer-triggering industrial pollutants, say US researchers.

Cold temperatures were also believed to help the chemicals precipitate out of the atmosphere and fall to the ground.

Dr Sophie St-Hilaire, who led the scientists from Idaho State University, said: "We found that colder weather, and low rainfall, were strongly correlated with prostate cancer.

"Although we can't say exactly why this correlation exists, the trends are consistent with what we would expect given the effects of climate on the deposition, absorption, and degradation of persistent organic pollutants including pesticides".

Around one in six men will develop prostate cancer in their lifetime.

Across the northern hemisphere, reported incidence of the disease is greater in higher latitudes, according to the scientists.

Each year in the UK, around 35,000 men are diagnosed with prostate cancer and 10,000 die from the disease.

It is known that some persistent organic pollutants can cause cancer, said the researchers writing online in the International Journal of Health Geographics.

Experts believed that cold weather slowed the chemicals' degradation and caused them to precipitate to the ground.

Rain and humidity were also thought to play important roles in their absorption and degradation.

Dr St-Hilaire said: "This study provides an additional hypothesis for the north-south distribution of prostate cancer, which builds on the existing supposition that individuals at northern latitudes may be deficient in Vitamin D due to low exposure to UV (ultraviolet) radiation during the winter months.

"Our study suggests that in addition to vitamin D deficiency associated with exposure to UV radiation, other meteorological conditions may also significantly affect the incidence of prostate cancer".

The scientists analysed prostate cancer data for every US county between 2000 and 2004.

They found that lower temperatures correlated with higher rates of prostate cancer, after adjusting for UV radiation, local pesticide use, rainfall, snowfall and other factors.

"We hypothesise that temperature may be associated with the incidence of prostate cancer by modulating exposure to POPs (persistent organic pollutants), some of which have been linked to the disease," the researchers wrote.

Organic chemicals tended to exist in a solid rather than a gaseous form at cold temperatures, they pointed out. This would cause them to fall to earth.

Temperature also affected the degradation of POPs in the soil and atmosphere.

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