title: Obesity and hormone-dependent tumors: cohort and co-twin control studies based on the Swedish Twin Registry.
abstract: Obesity increases the risk of certain cancer types, e.g., cancer of the endometrium, colon and gallbladder. For some other cancer forms, e.g., prostate cancer, the association is less clear. We examined the association between body mass index (BMI) and hormone-dependent tumors, utilizing a cohort of 21,884 Swedish twins born during 1886-1925. Information about BMI at different ages and potential confounding factors was collected prospectively. The Swedish Cancer Registry was used to identify cases of cancer in the prostate (n = 666), breast (n = 607), corpus uteri (n = 150) and ovary (n = 118) during 1969-1997. The material was analyzed as a traditional cohort and with co-twin control analyses that allow for control of genetic influences. Obesity (BMI >/=30 kg/m(2)) at baseline was positively associated with cancer in the corpus uteri [relative risk (RR) = 3.03, 95% confidence interval (CI) 1.82-5.03], as was BMI at age 25, independently of BMI at baseline. Increased risk was also found for breast cancer but only in older women (>/=70 years). Overweight at age 25 was associated with decreased risk of breast cancer (RR = 0.51, 95% CI 0.33-0.78). No association was found for prostate cancer. We conclude that age is an important effect modifier of cancer risk associated with obesity and that obesity and overweight in young adult life may affect cancer risk also later in life.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Jonsson
authors.affiliation: Department of Medical Epidemiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
authors.affiliation: Department of Medical Epidemiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Pedersen
authors.affiliation: Department of Medical Epidemiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: Department of Epidemiology and Social Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Terry
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Ahlbom
authors.affiliation: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Feychting
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology; D016022:Case-Control Studies; D015331:Cohort Studies; D004200:Diseases in Twins / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009376:Neoplasms, Hormone-Dependent / Q000453:epidemiology* / Q000209:etiology; D009765:Obesity / Q000453:epidemiology* / Q000209:etiology; D010051:Ovarian Neoplasms / Q000453:epidemiology / Q000209:etiology; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000453:epidemiology / Q000209:etiology; D012042:Registries; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology