Higher fitness levels among middle-aged men might be associated with a lower risk for later lung and colorectal cancer, but not prostate cancer, according to a new study. The study also linked higher fitness levels in midlife to a lower risk for later death from cancer or cardiovascular disease.
The findings were published online March 26 in JAMA Oncology.
This study is the first to show that cardiorespiratory fitness (CRF) predicts the incidence of certain types of cancer and the risk for death from cancer or cardiovascular disease after being diagnosed with cancer, the authors report.
"Among the men who developed cancer, those who were more fit at middle age had a lower risk of dying from all three cancers studied, as well as from cardiovascular disease," said first author Susan G. Lakoski, MD, MS, from the University of Vermont in Burlington, working with colleagues at the Cooper Institute in Dallas.
"Even a small improvement in fitness (by 1-MET) made a significant difference in survival, reducing the risk of dying from cancer by 10% and from cardiovascular disease by 25%," she told Medscape Medical News.
A 1-MET difference equates to the difference between running an 11.5-minute mile (9 METS) and a 12.0-minute mile (8 METS), Dr Lakoski explained.
Dr Lakoski, a former professional athlete for whom training has "always been an important part of my life," revealed that her training has evolved over the years because of age-related changes and work schedules.
"I understand the importance of staying committed to a regular exercise routine," she said, "I know my limits and how hard to push myself based on my prior fitness testing, which we advocate for in this study."
The study used information from the Cooper Center Longitudinal Study, which was conducted at a preventive medicine clinic in Dallas. It involved 13,949 men who underwent comprehensive medical examination, cardiovascular risk assessment, and treadmill testing to evaluate CRF from 1971 to 2009. The mean age of the participants was 49 years, and 98% of the cohort was white.
The researchers used Medicare claims data from 1999 to 2009 to assess lung, prostate, and colorectal cancer diagnosed in people 65 years and older.
Over a follow-up period of 6.5 years, 1310 men developed prostate cancer, 200 developed lung cancer, and 181 developed colorectal cancer.
The study revealed that a high CRF in midlife, compared with a low CRF, led to a 55% reduction in lung cancer (adjusted hazard ratio [HR], 0.45; 95% confidence interval [CI], 0.29 - 0.68) and a 44% reduction in colorectal cancer (adjusted HR, 0.56; 95% CI, 0.36 - 0.87). This association did not apply to prostate cancer (adjusted HR, 1.22; 95% CI, 1.02 - 1.46; P = .0004).
"The relations between fitness and prostate cancer risk is controversial," Dr Lakoski explained. "It is possible that men with higher CRF are more likely to undergo more frequent preventive healthcare screening and/or detection visits, and have a greater opportunity to be diagnosed with localized prostate cancer than men with lower CRF."
However, men who developed prostate cancer had a lower risk of ultimately dying from cancer or cardiovascular disease if they had higher fitness levels before diagnosis, she pointed out.
"This speaks to the importance of being fit in mid-life to improve survival, even if a man ultimately develops lung, prostate, or colorectal cancer later in life," Dr Lakoski continued.
In addition, a high CRF in midlife, compared with a low CRF, was associated with a 32% reduction in all cancer-related death in men 65 years and older who developed lung, colorectal, or prostate cancer (adjusted HR, 0.68; 95% CI, 0.47 - 0.98). And a high CRF was associated with a 68% reduction in death from cardiovascular disease after receiving a cancer diagnosis (adjusted HR, 0.32; 95% CI, 0.16 - 0.64).
Study limitations include the inability to assess the length and intensity of smoking, cancer stage, changes in CRF from the initial health screening to cancer diagnosis, and outcomes that occurred between study entry and Medicare eligibility.
"We did not capture the individual workouts of each participant," Dr Lakoski reported. "However, it is known that increasing both the intensity and duration of exercise improves fitness levels. Patients should talk to their physician about what amount of exercise is right for them to start with. This is the key first step."
"We propose that fitness testing is an objective guide to help physicians counsel their patients on this topic," she emphasized. "These findings provide support for the utility of CRF assessment in preventive healthcare settings, and possibly following a diagnosis of cancer."
"Future studies are needed to test these results across all major cancers in men and women, and to address how much an individual must change their fitness to see cancer prevention benefit," she concluded.
Dr Lakoski reports receiving partial funding from the National Institute of General Medical Sciences/National Institute of Health. Dr Jones reports receiving research grants from the National Cancer Institute.
JAMA Oncol. Published online March 26, 2015. Abstract
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Cite this: Higher Fitness Levels Linked to Lower Risk of Some Cancers and Death - Medscape - Mar 26, 2015.