June 2016, Vol. 5, No. 5

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Walking Reduces Markers of Inflammation in Smokers with Lung Cancer

AACR

If you can’t get your lung cancer patients to stop smoking, at least encourage them to exercise. That’s the message from research conducted on a huge cohort of individuals in the National Health and Nutrition Examination Survey (NHANES), showing that markers of inflammation were significantly reduced among male smokers with lung cancer if they exercised.

The interesting findings were presented at the American Association for Cancer Research Annual Meeting by Marisa A. Bittoni, PhD, of The Ohio State University Comprehensive Cancer Center.

“Our results are in line with those of our [previous] prospective cohort study, which showed substantial reductions in lung cancer deaths (30%-50%) from increased physical activity and healthier eating, primarily in smokers and males,” Dr Bittoni said. “The theory was that smokers with lung cancer had more of an inflammatory environment because of the smoking.”

Little effect was observed among females, especially nonsmokers, she added.

Inflammation and Cancer

Chronic inflammation is associated with adverse lifestyle factors, including poor diet, lack of physical activity, and smoking. Systemic inflammation plays an impor­tant role in carcinogenesis for several cancers, including lung cancer. C-reactive protein (CRP) is an acute-phase protein that is elevated in response to acute inflammation, infection, and tissue damage. CRP levels have been shown to be moderately elevated in persons with chronic inflammatory diseases, including cancer, the researchers noted.

The purpose of this study was to simultaneously examine the associations between lifestyle factors and CRP levels and to look for differences according to smoking and gender, she said.

Third NHANES

Data from cancer-free individuals aged 40 years and older in the Third NHANES (1988-1994) were examined to assess relationships between exercise habits, dietary patterns (measured by the Healthy Eating Index), and inflammation.

The researchers identified 5405 persons with normal CRP (<3 mg/L) and 3545 with elevated levels (CRP ≥3 mg/L).

Elevated CRP was more likely among smokers (56.5%) than nonsmokers (53.6%; P <.0001). Persons with poor diets were also more likely to have elevated CRP (35.7%) versus normal CRP (31.4%), whereas the reverse was true for those with healthy diets, in whom elevated CRP rates were low (31.7%) and normal CRP rates were higher (34.8%; P <.0001).

In the multivariate analysis, smoking raised the risk of having elevated CRP by 41% (P <.0001), and exercise reduced the risk by 22% (P = .0001).

Other types of physical activity were also significantly related to lower CRP levels, but walking had the strongest association. In the univariate analysis, the odds ratio (OR) for walking 1 mile within the past 30 days was 0.43.

Although walking for 1 mile in the past month is not a very strenuous definition of physical activity, Dr Bittoni acknowledged, she suggested that a “yes” answer may identify persons who tend to exercise more regularly.

With regard to other lifestyle factors, the OR estimates for selenium remained similar and statistically significant in all groups (P <.05). The ORs for serum vitamin D levels (OR = 0.90; P <.01) and Healthy Eating Index score (OR = 0.92; P = .001) were only significant for smokers and males.

The greatest effect on CRP levels, she reiterated, was seen with walking, “which was out-doing healthy eating” as a means of reducing inflammation.

Reduction in inflammation is important, she emphasized. “Inflammation is part of the tumor microenvironment,” she said. “If you reduce inflammation, you reduce the chance of getting cancer. Anything that does that should be helpful.”

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