Study hints demographic link in California county.(high rate of breast cancer in Marin County may be linked to population type)

2003 JAN 2 - (NewsRx.com & NewsRx.net) -- Suspicions that something in the environment is causing Marin County's high rate of breast cancer have led to a big fund drive and public awareness campaign. But some scientists say the people, not the place, are the reason for the cancer levels.

Some community activists have pronounced well-to-do Marin County "the breast cancer capital of the world" and are worried the air or the water is to blame. But some researchers who have studied the county doubt it.

"It's not the geography; it's the demography," said Tina Clarke, an epidemiologist at the Northern California Cancer Center in Union City, which monitors cancer rates in Marin and eight other San Francisco Bay area counties. "It's the type of person living in Marin County."

Many studies have suggested that breast cancer more often strikes highly educated, middle-class women, in part because they have children late in life or not at all, have greater access to hormone supplements and are more likely to regularly drink alcohol.

And Marin County, where incomes are twice the national average and the median single-family home costs $530,000, has an unusually high%age of highly educated, middle-aged white women with these and other risk factors among its population of 250,000.

Marin's cancer rate leaps out among other California counties, but researchers find similar rates in other relatively homogenous pockets of upper middle-class white women, said Clarke, whose research has been funded by the National Cancer Institute.

The average number of new breast cancer cases reported in Marin County each year was 199 out of every 100,000 white females from 1995 to 1999, compared with 143 per 100,000 white females in the rest of urban California, a number that is on track with the rest of the nation, Clarke said.