J. Kellogg Parsons, MD
Self-reported physical activity significantly improved the odds that a person would not die of bladder cancer, a review of a national health information database showed.
People who exercised had almost a 50% lower risk of bladder cancer death as compared with survey respondents who reported no physical activity. Neither obesity nor being overweight had a significant association with bladder cancer mortality in people who were initially cancer free.
Consistent with previous reports, smoking was associated with a significant increase in the mortality hazard for bladder cancer, although smoking cessation partly mitigated the effect, according to a presentation at the American Urological Association meeting.
“We interpret these findings to mean that if you got any amount of exercise at all, you were half as likely to die of bladder cancer,” said J. Kellogg Parsons, MD, an associate professor of Surgery (urology) at the University of California, San Diego.
Physical activity has been associated with a reduced risk of prostate cancer and prostate cancer mortality. In contrast, the relationship of physical activity and obesity to bladder cancer risk has not been studied extensively. Clarification of the associations could help identify modifiable risk factors for bladder cancer mortality, beyond the established association with smoking, said Parsons.
“We have reached the point in prostate cancer that we are running translational studies,” he said. “There is relatively little data on lifestyle and bladder cancer. There is a fair amount of data in the epidemiological literature, but nothing on the clinical side. Very surprisingly, there is very little information on obesity and exercise and bladder cancer mortality.”
To examine relationships between physical activity, obesity, and bladder cancer mortality, investigators searched the database for the National Health Information Survey (NHIS), an annual cross-sectional household interview survey of a representative national population sample. They analyzed data for 222,163 survey participants from 1998 through 2004 and linked the information to mortality data for deaths reported through 2006.
Physical activity had a dichotomous definition: “none” versus “light, moderate, or vigorous exercise” for at least 10 minutes per episode. Secondarily, Parsons and colleagues examined the association between smoking and bladder cancer mortality.
The definitions of obesity and overweight were derived from body mass index (BMI). The primary outcome of interest was bladder cancer-specific mortality. All of the participants were free of bladder cancer at baseline.
Women accounted for a majority of the sample (125,448), and non-Hispanic whites made up almost three fourths of the population (146,014).
During the follow-up period, 83 study participants developed fatal bladder cancer. The analysis showed that NHIS participants who reported exercising had a 47.6% lower risk of bladder cancer mortality compared with participants who reported getting no exercise (HR=0.526, P
In contrast to studies showing associations between obesity and prostate cancer, analysis of the NHIS data showed no association for obesity or overweight with bladder cancer-specific mortality. Obese patients (as defined by BMI) had about a 6% higher risk of dying of bladder cancer as compared with nonobese study participants, but the difference did not reach statistical significance (HR= 1.057, P
=.8693). Overweight participants actually had a nonsignificant trend toward lower bladder cancer mortality (HR= 0.609, P
The data also showed that current smokers had a fourfold increased risk of bladder cancer mortality compared with nonsmokers (HR=4.236, P
=.0006). The risk remained significantly elevated in nonsmokers, but suggested a beneficial effect of smoking cessation (HR=2.945, P
Parsons pointed out several limitations of the study. None of the participants had bladder cancer at enrollment, so the data do not reflect potential effects of physical activity and weight on cancer-specific mortality among patients with existing bladder cancer. The data also did not include a link to tumor stage.
Despite the caveats, studies of lifestyle interventions in bladder cancer would be worthwhile, said Parsons. Translational studies might provide information about potential biological pathways that mediate associations between lifestyle factors and bladder cancer mortality.
A previous study has demonstrated the feasibility of conducting a lifestyle intervention trial in bladder cancer. Parsons and colleagues reported that an intervention study demonstrated dietary changes associated with protective effects against bladder cancer, specifically, increased consumption of fruit and vegetables and reduced intake of dietary fat (Cancer Prev Res. 2013;6:971-978).