The majority of women do not meet national exercise recommendations 10 years after their breast cancer diagnosis despite the fact that these patients can greatly benefit from physical activity, researchers have found.

Physical activity is associated with reduced mortality and higher quality of life in survivors of breast cancer, but limited data on the prevalence of activity and long-term trends after diagnosis are available, explained epidemiologist Caitlin Mason, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, Washington, and colleagues in Cancer Epidemiology, Biomarkers & Prevention. The team gathered more information by following for 10 years a multiethnic cohort of 631 women, aged 18 to 64 years, with stage 0-IIIA breast cancer.

Before diagnosis (baseline), 34% of the participants met physical activity guidelines of at least 150 minutes of moderate activity per week or at least 75 minutes of vigorous activity per week. At 24 months after study enrollment, 34% continued to meet the guidelines, as did 39.5% at the 5-year mark.

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But the investigators were surprised to find a large drop in activity at 10 years, when only 21.4% of the women were exercising in keeping with guidelines.

Meeting physical activity guidelines before breast cancer diagnosis was strongly associated with meeting the guidelines at 5 years and 10 years. However, after accounting for such factors as age and body size at diagnosis, Mason and associates found that no other demographic factors or characteristics related to type of breast cancer or type of treatment were significantly associated with the decline in activity between the 5-year and 10-year reporting periods.

The authors wrote that aging alone was unlikely to account for this pattern, given the consistency and magnitude of the trend across all age groups.

Over the course of 10 years, recreational aerobic activity fell by a mean 4.3 metabolic-equivalent hours per week (MET hrs/wk).

“The American Cancer Society recommends that cancer survivors exercise for at least 150 minutes per week,” noted Mason in a Hutchinson statement. “Most survivors may also benefit from strength-training exercises at least 2 days per week.”

Patients who had not previously been physically active should gradually work up to meeting these recommendations.