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Cancer Epidemiol. 2013 Feb;37(1):46-53. doi: 10.1016/j.canep.2012.09.003. Epub 2012 Oct 30.

Recreational physical activity and risk of papillary thyroid cancer among women in the California Teachers Study.

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1
Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA 98195, USA.

Abstract

PURPOSE:

Little is known about the relationship between physical activity and thyroid cancer risk, and few cohort data on this association exist. Thus, the present study aimed to prospectively examine long-term activity and risk of papillary thyroid cancer among women.

METHODS:

116,939 women in the California Teachers Study, aged 22-79 years with no history of thyroid cancer at cohort entry, were followed from 1995-1996 through 2009; 275 were diagnosed with invasive papillary thyroid cancer. Cox proportional-hazards regression provided relative risk (RR) estimates and 95% confidence intervals (CI) for associations between thyroid cancer and combined strenuous and moderate recreational physical activity both in the long-term (high school through age 54 years or current age if younger than 54 years) and recently (during the three years prior to joining the cohort).

RESULTS:

Overall, women whose long-term recreational physical activity averaged at least 5.5 MET-hours/week (i.e. were active) had a non-significant 23% lower risk of papillary thyroid cancer than inactive women (RR = 0.77, 95% CI: 0.57, 1.04). RR estimates were stronger among normal weight or underweight women (body mass index, BMI<25.0 kg/m(2), trend p = 0.03) than among overweight or obese women (trend p = 0.35; homogeneity-of-trends p = 0.03). A similar pattern of risk was observed for recent activity (BMI<25 kg/m(2), trend p = 0.11; BMI≥25 kg/m(2), trend p = 0.16; homogeneity-of-trends p = 0.04). Associations for long-term activity did not appear to be driven by activity in any particular life period (e.g. youth, adulthood).

CONCLUSIONS:

Long-term physical activity may reduce papillary thyroid cancer risk among normal weight and underweight women.

PMID:
23116823
PMCID:
PMC3543486
DOI:
10.1016/j.canep.2012.09.003
[Indexed for MEDLINE]
Free PMC Article
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