Aug. 19, 2011 -- An unprecedented drop in the number of women getting mammograms was due to women going off hormone replacement therapy (HRT), a new study suggests.
But in 2005, researchers were astonished to see that fewer women were getting mammograms. What happened has been a mystery until now.
In a new study, National Cancer Institute researcher Nancy Breen, PhD, and colleagues finger the culprit: hormone replacement therapy.
"A change in hormone therapy use was associated with the drop in mammography use for women ages 50 to 64 years, but not for women age 65 years and older," Breen and colleagues report in the early online edition of the journal Cancer.
In 2002, results from the Women's Health Initiative study linked HRT to increased risk of breast cancer. The result was that 6.4 million women ages 50 to 64 and 2 million women ages 65 and older suddenly stopped hormone therapy.
Since a woman needs a prescription to get HRT, women had to see a doctor every year. And the most important factor in whether a woman gets a mammogram is whether her doctor recommends it.
Using data from the National Health Interview Surveys from 2000 and 2005, Breen and colleagues found a statistical link between stopping HRT and getting a mammogram -- but only for women ages 50 to 64.
That solves one mystery, but not another. In 2008, and again in 2010, mammography rates went back up even higher than they had been in 2005. Yet there appears to have been no increase in HRT use.