The percentage of women receiving annual mammograms fell by as much as 4 percent between 2000 and 2005, according to a new study.

The decline in screening coincides with reported decline in the incidence of breast cancer.

Breast cancer screening rates for women over the age of 40 steadily increased from 1987 to 2000 from 39 percent to 70 percent, according to the study, published in the June 15 issue of “Cancer,” a peer-reviewed journal of the American Cancer Society.

While screening rates were relatively flat from 2000 to 2003, the percentage of women getting mammograms in 2005 fell to about 66 percent.

The decline was significant for women over the age of 50. Some of the steepest declines were seen in women who previously reported high screening rates, including those between the ages of 50 and 64 and those with higher socioeconomic levels.

The study’s author, Dr. Nancy Breen of the National Cancer Institute, and her co-authors said in the “Cancer” article that they are “concerned that some of the observed decline in the incidence (of breast cancer) may be due in part to the leveling off and reduction in mammography rates."

Researchers from the University of Texas MD Anderson Cancer Center said last December that national breast cancer rates declined 7 percent between 2002 and 2003. The decline coincided with a decline in the use of hormone replacement therapy.

National Cancer Institute researchers added that regular mammograms, which can detect tumors that are too small to be felt during a physical exam, are the most effective means of early detection. They say the decline in screenings puts a previous decline in breast cancer mortality rates at risk.