title: Leisure-time physical activity and endometrial cancer risk: dose-response meta-analysis of epidemiological studies.
abstract: Although considerable evidence suggests that leisure-time physical activity is associated with a reduced risk of endometrial cancer (EC), the shape of dose-response relationship has not been investigated and previous meta-analyses have not accounted for differences in measures of physical activity. To address such issues, we conducted linear and nonlinear dose-response meta-analyses by metabolic equivalent of task (MET)-hour/week and hour/week, respectively, based on observational studies published up to September 2013 identified from PubMed and Embase databases. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using a random-effects model. In the linear dose-response analysis, an increase in leisure-time physical activity by 3 MET-hour/week was associated with an ∼2% reduced risk of EC (summary RR = 0.98, p = 0.02, 95% CI = 0.95-1.00, I(2)  = 53%, p(heterogeneity)  = 0.06, three case-control studies and three cohort studies, 3,460 cases, range of activity = 0-50 MET-hour/week) and an increase by an hour/week was associated with an ∼5% reduced risk of EC (summary RR = 0.95, p < 0.001, 95% CI = 0.93-0.98, I(2)  = 31%, p(heterogeneity)  = 0.20, four case-control studies and two cohort studies, 3,314 cases, range of activity = 0-12 hour/week). Nonlinear dose-response meta-analysis suggested that the curve may plateau at 10 MET-hour/week (p(change) in slope  = 0.04) but this statistical significance was sensitive to one study. No evidence of a nonlinear association was indicated by hour/week (p(change) in slope  > 0.69). In conclusion, an increase in leisure-time physical activity may continue to decrease EC risk, within the range of 0-50 MET-hour/week or 0-15 hour/week. Future studies should evaluate possible independent role of intensity of physical activity and effect modification by obesity.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, MA; Department of Epidemiology, Harvard School of Public Health, Boston, MA.
authors.forename: NaNa
authors.initials: N
authors.lastname: Keum
authors.forename: Woong
authors.initials: W
authors.lastname: Ju
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Lee
authors.forename: Eric L
authors.initials: EL
authors.lastname: Ding
authors.forename: Chung C
authors.initials: CC
authors.lastname: Hsieh
authors.forename: Julie E
authors.initials: JE
authors.lastname: Goodman
authors.forename: Edward L
authors.initials: EL
authors.lastname: Giovannucci
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D016889:Endometrial Neoplasms / Q000453:epidemiology* / Q000209:etiology; D015444:Exercise; D005260:Female; D006801:Humans; D007899:Leisure Activities; D011379:Prognosis; D012307:Risk Factors; D013997:Time Factors; D014481:United States / Q000453:epidemiology
keywords: dose-response; endometrial cancer; meta-analysis; physical activity