235931 Long-term physical activity and reduced risk of invasive papillary thyroid cancer in the California Teachers Study

Tuesday, November 1, 2011

Stephanie Whisnant Cash, MPH , Department of Epidemiology, University of Washington, Seattle, WA
Huiyan Ma, PhD , Division of Cancer Etiology, Department of Population Sciences, Beckman Research Institute, City of Hope, Duarte, CA
Pamela Horn-Ross, PhD , Cancer Prevention Institute of California, Fremont, CA
Peggy Reynolds, PhD , Cancer Prevention Institute of California, Fremont, CA
Alison Canchola, MS , Cancer Prevention Institute of California, Fremont, CA
Jane Sullivan-Halley, BS , Division of Cancer Etiology, Department of Population Sciences, Beckman Research Institute, City of Hope, Duarte, CA
Shirley Beresford, PhD , Department of Epidemiology, University of Washington, Seattle, WA
Marian Neuhouser, PhD , Cancer Prevention, Fred Hutchinson Cancer Research Center, Seattle, WA
Thomas Vaughan, MD , Program in Epidemiology, Fred Hutchinson Cancer Research Center, Seattle, WA
Patrick Heagerty, PhD , Department of Biostatistics, University of Washington, Seattle, WA
Leslie Bernstein, PhD , Division of Cancer Etiology, Department of Population Sciences, Beckman Research Institute, City of Hope, Duarte, CA
Background: Evidence is mixed concerning physical activity's relation to thyroid cancer. Methods: 116,947 participants of the California Teachers Study cohort, women ages 22 to 79 years with no history of thyroid cancer at baseline (1995-1996), were followed through 2007; 231 were diagnosed with invasive papillary thyroid cancer. Cox proportional hazards regression was used to estimate relative risks (RR) and 95% confidence intervals (95% CI) for associations between thyroid cancer and long- term (high school to age 54 years or current age for younger women) and recent combined strenuous and moderate recreational activity. Results: Women averaging at least 30 min/wk/yr of long-term activity were less likely to develop invasive papillary thyroid cancer than women averaging less than 30 min/wk/yr (RR=0.71, 95% CI: 0.51, 0.99). Inclusion of BMI in the model did not attenuate the risk estimate, but BMI modified the physical activity-thyroid cancer association (interaction p=0.050). The association was restricted to women with body mass index (BMI) under 25 kg/m2 (RR=0.64, 95% CI: 0.42, 0.99; trend p=0.047 over 4 categories). No associations with long-term activity were observed for overweight or obese women (BMI > 25 kg/m2). Recent physical activity was not associated with risk of invasive papillary thyroid cancer. Conclusions: Although several studies have examined physical activity and papillary thyroid cancer risk, this is the first prospective study to assess long-term participation in physical activity. Long-term activity may reduce the risk of papillary thyroid cancer in a dose-response manner in normal weight and underweight, but not overweight or obese, women.

Learning Areas:
Chronic disease management and prevention
Epidemiology
Social and behavioral sciences

Learning Objectives:
Describe the relationship between physical activity and risk of thyroid cancer in women, explain how this association differs for normal weight and overweight/obese women, and discuss potential biologically plausible reasons for the associations observed.

Keywords: Physical Activity, Cancer Prevention

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I am a fourth year graduate student writing my dissertation on physical activity and cancer prevention, including thyroid cancer prevention and DNA damage/repair.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.