NOVATO — Breast cancer rates in Marin County have jumped 20 percent in one year, increasing the already-high rates for the county, according to a recent study.
The increase was mostly among women between 45 and 64 years old. Marin County’s breast cancer rates in that age group have been 58 percent higher than other parts of the San Francisco Bay Area and 72 percent higher than other urban areas of California.
The reasons for the high rates are unclear. They could be due to better health screening, demographic factors or statistical flaws.
The Northern California Cancer Center compiled statistics on cancer rates using census data and county health records.
Tina Clarke, an epidemiologist for the center, said the higher rates could be due to a large number of women in the county who have characteristics associated with breast cancer, such as being white, having fewer children, having children later in life, and higher education or household income.
Also, there could be a wider use of mammograms in Marin, which could mean that more cancer is being caught earlier.
But more people are dying from breast cancer in Marin. The death rates there are 25 percent higher than around the Bay Area and other urban areas of the state.
Breast cancer rates in the county increased 60 percent between 1991 and 1999.
In the spring, Marin Breast Cancer Watch is expected to release its study of adolescent risk factors in developing breast cancer, and it’s also working with the Lawrence Berkeley National Laboratory on a study by the county and the Centers for Disease Control to examine the possible relationship between breast cancer risk and exposure to environmental risk factors.