- Jennifer Middleton, MD, MPH
You may have heard about a study examining the correlation among lifestyle habits and cancer that has been making headlines in both the medical and lay press this past week; the researchers found that individuals who met their criteria of a "healthy lifestyle pattern" had significantly lower risk of developing multiple types of cancers. This finding should further bolster our efforts to provide lifestyle counseling to our patients.
The study researchers examined data from the Nurses' Health Study (NHS) and the Health Professionals Follow-up Study (HPFS), both large U.S. population cohorts. The NHS has been following female nurses since 1976, and the HPFS has been following male health professionals since 1986. Both cohorts are composed of entirely white individuals. The researchers divided each cohort into two groups: those enrollees who met 4 criteria for a "healthy lifestyle pattern" (never smoked or less than 5 pack-years of smoking, no or moderate alcohol intake, BMI between 18 and 27.5, and at least 75 minutes of vigorous aerobic activity a week and/or 150 minutes of moderate physical activity a week) and everyone else, that is, those who did not meet all 4 criteria and therefore fell into the "high risk group." Since they assumed that even the high risk group might still follow healthier behaviors compared to the general population, given that the cohort enrollees all worked in the health professions, they also compared their findings against the U.S. white population as a whole.
The researchers included most cancers in their analyses but excluded skin, brain, lymphatic, and hematopoietic cancers ("because these cancers likely have other strong environmental causes"), along with non-fatal prostate cancers ("given the concern for overdiagnosis...by prostate-specific antigen screening"). 18.5% of the women fell into the healthy lifestyle group, compared to 25.3% for men. 4.6% of the women in the healthy lifestyle group developed cancer compared to 6.2% of women in the high risk group and 7.9% of women in the general US white population; 2.8% of the men in the healthy lifestyle group developed cancer compared to 4.3% in the high risk group and 7.6% in the general US white population. The risk of mortality from cancer follows a similar trend for both genders. The numbers that have been widely quoted in the media in the last week, the population attributable risk, suggests a 20-40% lower cancer incidence and an approximately 50% lower cancer mortality rate among the healthy lifestyle groups compared to the high risk groups. It's not necessarily unreasonable to extrapolate these results to non-white populations, but hopefully future studies will include a more diverse population.
It's important to remember that cohort studies can demonstrate an association or correlation between risk factors and disease, but they cannot definitively prove causation in and of themselves. Regardless of this caveat, the media coverage of this study (which rarely seems to include this point) may still spur more patients to discuss lifestyle counseling with us. The current issue of AFP reviews the recent United States Preventive Services Task Force (USPSTF) recommendations regarding tobacco smoking cessation, which serves as a good reminder that even brief behavioral interventions can help our patients quit smoking. Physicians and their staff can maximize the efficacy of behavioral interventions by providing them repeatedly, since the intensity of counseling does correlate with quit rates. Providing nicotine replacement therapy is also an effective option for helping patients quit.
Many patients may already connect tobacco use with an increased risk for cancers, but I suspect few relate excessive alcohol use, obesity, and/or lack of exercise to an increased cancer risk. Discussing this study's findings with patients may help encourage lifestyle changes, since fear of developing cancer generally ranks quite high among our patients' health concerns. Here are some recent AFP articles that provide additional information regarding counseling for excessive alcohol use, obesity, and exercise. For more in-depth reading, check out the AFP By Topics on Alcohol Abuse and Dependence, Obesity, and Health Maintenance and Counseling.