Evaluation of dietary, medical and lifestyle risk factors for incident kidney cancer in postmenopausal women.

Kidney cancer incidence rates in the United States have been increasing and are not fully accounted for by better diagnostic techniques. Risk factors in women are incompletely described. A total of 34,637 Iowan women initially free of cancer completed a mailed questionnaire in 1986. Kidney cancer incidence was identified over 15 years of follow-up (n = 124) through linkage to a statewide cancer registry. Adjusted for age and other risk factors, kidney cancer was associated positively with maximum adult weight (p for trend = 0.02) and current waist-to-hip ratio (p for trend = 0.002). Compared to nondrinkers, consumers of alcohol of 3.0 or more grams per day had a relative risk (RR) of 0.52 (95% CI = 0.29-0.92). Total vitamin C intake was associated positively with risk of kidney cancer (p for trend = 0.04), whereas total vitamin E intake was associated negatively with risk (p for trend = 0.002). The few women who used copper supplements had a 6.52-fold increase in risk of kidney cancer (95% CI = 1.95-21.8). Compared to never users, women who were former users of estrogen had an increased risk of kidney cancer (RR = 1.62; 95% CI = 1.11-2.36), but current users of estrogen were not at a higher risk. Women who were nulliparous or had more than 2 live births were also at increased risk of kidney cancer compared with women who had 1 or 2 live births. In conclusion, in these postmenopausal women, overweight, particularly central adiposity, was an important risk factor for kidney cancer. Potential risk factors that warrant further exploration were low intake of alcohol and vitamin E, higher intake of vitamin C, nulli- or multiparity and use of copper supplements. Copyright 2003 Wiley-Liss, Inc.