Geographic Influences on Women's Health
University of Massachusetts
School of Public Health, Amherst, Mass.
Dr. Susan Sturgeon, of the University of Massachusetts School of Public Health, Amherst, Mass., conducted a study to determine the extent to which variation in the prevalence of breast cancer risk factors was responsible for regional differences in breast cancer mortality rates. She began this study while working at the National Cancer Institute.
The study focused chiefly on geographic variations among white women in the Northeast and South — where differences in breast cancer death rates are most pronounced, and on rural and urban variations in rates in these regions.
Breast cancer death rates for white women vary substantially by region of the country and population density. (View maps.) In 1985-1989, rates for women in the Northeast were 20 percent higher than in the South, which had the lowest rates. Furthermore, rates tended to be higher in urban than rural areas within the same regions of the country. They also varied within counties with similar population densities and within the same region. Breast cancer death rates for black women did not differ as markedly by geographic area as for white women.
Dr. Sturgeon's study included 3,800 women, 25 years-of-age or older (selected by random digit dialing). About 300 women were from Nassau County, NY Between December 1994 and April 1995, the research team interviewed study participants by telephone for information about their age, menstrual and reproductive history, personal and family history of breast cancer, history of benign breast biopsies, exogenous estrogen use, body mass index, dietary fat intake, and alcohol consumption. The potential contribution of differences in the prevalence of breast cancer risk factors to population-density and count-level variation in the 1990-1994 breast cancer mortality rates was then analyzed.
Publishing their findings in 2003, the researchers reported that "higher breast cancer mortality rates in high-density areas relative to low-density areas among women 55 years and older in the Northeast and South were completely explained by the higher proportion of women with established breast cancer risk and prognostic factors in high-density areas. The most important factor was age at first livebirth." Among younger women, they added, little or no variation in breast cancer mortality rates were observed between low- and high-density areas either before or after adjustment for established breast cancer risk factors.
In addition, the researchers said, "County-level variation in breast cancer mortality rates in 1970-1979 within high-and low-density areas of the Northeast and South was considerably attenuated [weakened] when 1990-1994 mortality rates from the same group of counties were used. The same attenuation in the mortality ratios over time was seen for Nassau County. There was no statistically significant excess mortality in Nassau County compared to low-mortality, high-density areas in the Northeast using 1990-1994 rates after adjustment for known risk factors."
The Northeast area covered in the study includes Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New Hampshire, New York, Pennsylvania, Rhode Island, Vermont, and the District of Columbia. The southern states are Alabama, Arkansas, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and West Virginia.
The study above was a follow-up to a 1995 analysis by Dr. Sturgeon and colleagues of geographic differences in breast cancer death rates that demonstrated that the mortality risk for breast cancer among white women is similar in the Northeast, Midwest, and West, after recognized risk factors for the disease are taken into account. Moreover, the researchers found that the differences between these regions and the South narrowed after accounting for such factors. The study did not explain all the regional differences in breast cancer, but provided perspective and laid the groundwork for the present study.
The findings appeared in "Geographic Variation in Mortality from Breast Cancer Among White Women in the United States," Journal of the National Cancer Institute, by Drs. Sturgeon, Catherine Schairer, Mitchell Gail, et. al, December 20, 1995, vol. 87, no. 24, p. 1846-1853, along with an editorial, "Geographic Patterns of Breast Cancer Among Women," by Drs. William Blot and Joseph McLaughlin, p. 1819-1820 (no abstract available). Press Release