It may be a testament to effective breast cancer awareness
campaigns or aggressive research that while breast cancer is still the second most common cancer among American women, rates of diagnosis have been declining by about 2 percent each year since 1999.
Though doctors applaud the positive trend, many believe that identifying the cause for the decrease in breast cancer diagnoses could instigate a new wave of treatment or preventative advice.
A study by Harvard researchers that will appear in the April edition of the American Journal of Public Health theorized that the drop has been linked to the decreased use of menopausal hormone therapy since 2002, Newsweek reports.
"Our study can't settle the question," Nancy Krieger, an epidemiologist at Harvard's School of Public Health and the study's lead author, told the news source.
She added that despite clinical proof, the research "does show trends that make it hard to imagine any other explanation for the fall in these rates."
Specifically, the investigators find that the drop in breast cancer diagnoses occurred most commonly in affluent white women over 50, who were the most likely to be taking hormones during menopause.
The widespread use of hormone therapy dropped sharply in 2002, when data from the federal Women's Health Initiative study found a link between the therapy and an increased risk of breast cancer and heart disease.