title: Body mass index, physical activity, and risk of renal cell carcinoma.
abstract: OBJECTIVE
  To investigate the association between obesity and risk of renal cell carcinoma and to examine whether the association is modified by physical activity.
  
  
  METHODS
  A population-based case-control study of 406 patients with renal cell carcinoma and 2434 controls conducted in Iowa.
  
  
  METHODS
  Information was collected on weight at the ages 20-29, 40-49, and 60-69 years, height, nonoccupational physical activity, diet, and other lifestyle factors. Renal cell carcinoma risk was estimated by odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for age, total energy intake, and other confounding factors.
  
  
  RESULTS
  Height and total energy intake were not associated with risk in either sex. In men, neither physical activity nor level of obesity in any period of life was significantly associated with risk. In women, lower physical activity was associated with higher risk (OR=2.5; 95% CI=1.2-5.2 comparing exercise <1 time/month to >1 time/day). Compared with women in the lowest quartile for BMI, the risks of renal cell carcinoma for women in the highest 10% of BMI in their 20s, 40s, and 60s were 1.4 (CI=0.6-3.1), 1.9 (CI=0.9-4.2), and 2.3 (CI=0.9-6.0), respectively. When analyses were limited to self-respondent data, the corresponding ORs were 2.9 (CI=1.2-7.4), 3.2 (CI=1.3-7.5), and 2.1 (CI=0.7-6.4), respectively. There was little evidence that physical activity modifies the association of BMI with renal cell carcinoma.
  
  
  CONCLUSIONS
  Nonoccupational physical activity was inversely associated and obesity was positively associated with risk of renal cell carcinoma among women. The risk appeared to be greater for women in the highest 10% of BMI in their 40s. Our finding of little evidence of an interaction between physical activity and BMI requires confirmation.
authors.affiliation: Department of Preventive Medicine, Northwestern University Medical School, Chicago, IL, USA. bchiu@northwestern.edu
authors.forename: B C-H
authors.initials: BC
authors.lastname: Chiu
authors.forename: S M
authors.initials: SM
authors.lastname: Gapstur
authors.forename: W-H
authors.initials: WH
authors.lastname: Chow
authors.forename: K A
authors.initials: KA
authors.lastname: Kirby
authors.forename: C F
authors.initials: CF
authors.lastname: Lynch
authors.forename: K P
authors.initials: KP
authors.lastname: Cantor
mesh_terms: D000328:Adult; D000368:Aged; D000886:Anthropometry; D015992:Body Mass Index; D002292:Carcinoma, Renal Cell / Q000209:etiology*; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D004032:Diet; D002149:Energy Intake; D015444:Exercise; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000209:etiology*; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009765:Obesity / Q000150:complications*; D012307:Risk Factors; D012737:Sex Factors