Day: June 8, 2003

Marin County Breast Cancer Data Faulty

There has been a long-simmering controversy over breast cancer rates in Marin County, California. Marin County is one of the wealthiest counties in the United States and also has one of the highest breast cancer rates — 198 cases per 100,000 population compared to a national average of 139 per 100,000 for the rest of the country.

Activists who believe that pollution is a major contributor to breast cancer seized on this cancer cluster as evidence for their views, although a number of alternative explanations were possible. But now it turns out that there is an even better explanation — the data that claimed Marin County had a breast cancer incidence of 198 cases per 100,000 population appears to have been faulty.

The faulty data came to light after research in 2002 said that the rate of cancer for white women in Marin County had increased from 191 cases per 100,000 in 1998 to 230 cases per 100,000 in 1999. That sort of massive jump was extremely suspicious.

It turns out that such estimates had been using faulty data from the U.S. Census Bureau that dramatically undercounted the population of women in Marin County. Census data from 2000 showed that the 1990 estimates that such studies had been using underreported the number of white women 45-64 in Marin County by close to 20 percent. Revised breast cancer rates have not been released.

Ironically, another recent study of breast cancer among women in Marin County will also not please the activist who want pollution to be the cause and accuse researchers of “blaming the victim” anytime another cause is put forward.

A study by researchers at the University of California, San Francisco and published in the online journal Breast Cancer Research found a strong correlation between alcohol consumption and breast cancer among women in Marin County. Women who consumed two drinks a day had twice the breast cancer risk, and the risk increased with self-reported alcohol consumption.

That study was small, comparing 285 Marin County women with breast cancer to 286 healthy women living in the county. But it did find no correlation between breast cancer and length of time living in Marin County, suggesting the high breast cancer rate in Marin County has something to do with a confounding factor that women there share rather than something to do with Marin County itself.

Source:

Marin County breast cancer rates not as high as once thought. Justin Pritchard, Associated Press, April 4, 2003.

Study: Marin breast cancer related to alcohol consumption. Associated Press, May 7, 2003.

Mayo Clinic Study: Death Rate Among Anorexia Nervosa Patients Exaggerated

A Mayo Clinic study that looked at mortality rates among patients with anorexia nervosa over a period of 60 years concluded that people diagnosed with the disorder die at the same rate as people who do not have the disorder. This contradicts both previous clinical studies as well as many commonly cited claims that the death rate for people with the disorder is extremely high.

The commonly repeated claim is that individuals with anorexia nervosa have a mortality rate that is an astounding 12 times higher than the general population. But, as an epidemiologist with the Mayo Clinic points out, that is because previous studies were generally conducted in hospital settings where individuals with the most advanced cases of the disorder would be overrepresented.

Searching medical records, the Mayo Clinic identified 208 patients who met the criteria for an anorexia nervosa diagnosis between 1935 and 1989. The researchers found that those patients had the same death rate as the general population.

Mayo Clinic epidemiologist Joseph Melton said that,

Although our data suggest that overall mortality is not increased among community patients with anorexia nervosa in general, these findings should not lead to complacency in clinical practice because deaths do occur.

Patrick Sullivan, a professor of psychiatry and genetics at the University of Carolina at Chapel Hill, wrote in an editorial accompanying the study that what it showed was that anorexia nervosa symptoms occurred along a spectrum. Those with the most severe cases — such as those requiring hospitalization — may indeed have a higher mortality rate, but it is important to make distinctions between the degree of severity of the disease rather than lumping all cases in with the most severe and claiming that anyone with the disorder has a 12 times higher mortality rate.

Source:

Death rate for eating disorder not unusual. Brad Evenson, National Post (Canada), March 12, 2003.