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Chronic diseases account for more than 20% of cancer risk
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Eight common chronic diseases accounted for more than one-fifth of incident cancer risk, according to prospective study results.
These conditions increase cancer risk at a rate comparable to five major lifestyle factors, such as smoking and lack of physical activity.
Xifeng Wu, MD, PhD — professor, Betty B. Marcus chair in cancer prevention, and director of Center for Translational and Public Health Genomics at The University of Texas MD Anderson Cancer Center — along with Huakang Tu, PhD, postdoctoral fellow in epidemiology at MD Anderson, and colleagues conducted a prospective cohort study that included 405,878 participants in Taiwan.
Investigators assessed eight chronic diseases or markers: blood pressure, total cholesterol, heart rate, diabetes, proteinuria, glomerular filtration rate, pulmonary disease and gouty arthritis marker.
Average follow-up was 8.7 years.
All diseases and markers appeared significantly associated with cancer mortality, and all of them except for blood pressure and pulmonary disease appeared significantly associated with cancer incidence.
Results also showed physical activity reduced cancer incidence by nearly 50% and cancer mortality by more than one-quarter.
HemOnc Today spoke with Wu about the study, why chronic disease often is an overlooked risk factor for cancer, and the implications of these findings.
Question: How did you choose the chronic diseases to study?
Answer: We selected five common chronic diseases for evaluation based on their disease burden worldwide. Cancer — together with cardiovascular disease, diabetes, chronic kidney disease and respiratory disease — account for 83% of all chronic disease deaths. Additionally, other less fatal but common chronic diseases are among the leading causes of disability that severely affects quality of life. For example, 22.7% U.S. adults reported having doctor-diagnosed arthritis between 2010 and 2012, and 9.8% reported arthritis-attributable activity limitation. Gouty arthritis is the most common inflammatory arthritis worldwide.
Q: The finding that chronic disease is as much a risk factor as other key lifestyle factors is particularly striking. Can you expand on this?
A: In our study, we found the total contribution to cancer incidence from the eight chronic diseases or markers — a population-attributable fraction of 20.5% — was close to that of five major lifestyle factors. These factors — ever smoking, insufficient physical activity, insufficient fruit and vegetable intake, ever alcohol consumption, and nonideal BMI — account for a population-attributable fraction of 24.8%. The total contribution to cancer mortality from the eight chronic diseases or markers (population-attributable fraction, 38.9%) was also close to that of the five major lifestyle factors (population-attributable fraction, 39.7%).
Q: Why are chronic diseases not targeted in cancer prevention strategies?
A: Even though some previous studies have showed certain chronic diseases — such as diabetes — may predispose to cancer, cancer prevention strategies do not target chronic diseases, and this probably is because of the modest associations observed. Previous studies generally assessed chronic diseases or disease markers individually. As chronic diseases are typically clustered, it is necessary to study them simultaneously to elucidate their joint impact on cancer risk, but few data are available on this topic. Our study showed that the joint impact of common chronic disease and markers on cancer is substantial.
Q: Can you offer insights into the mechanisms that may explain why chronic disease can lead to cancer incidence ?
A: A common link between various chronic diseases and cancer could be chronic inflammation. In addition, different chronic diseases or markers may lead to cancer incidence through different mechanisms. For example, diabetes may increase cancer by several mechanisms, including hyperinsulinemia, hyperglycemia or chronic inflammation.
Q: What role does physical activity play in this population?
A: We assessed whether physical activity could reduce risk for incident cancer or cancer death associated with chronic diseases and markers, as indicated by summarized chronic disease risk scores. The positive associations of chronic disease risk scores with cancer incidence and cancer mortality were weaker among those who were physically active than those who were physically inactive. Physical activity attenuated the increased hazards by 38% to 54% — or an average of 48% — for cancer incidence, and 14% to 39% — for an average of 27% — for cancer mortality. Therefore, physical activity is associated with a nearly 40% reduction in the cancer risk associated with chronic diseases or markers.
Q: What must be done to make sure chronic disease is taken into account with regard to cancer risk and prevention?
A: First, we should consider reducing lifestyle risk factors to reduce the overall risk for cancer, as well as risks for other chronic diseases. Second, the recognition that chronic diseases have substantial impact resulting in reduced life span and increased cancer risk could be used as a teachable moment to stimulate motivation for better management of chronic diseases to reduce cancer burden and to improve health. – by Rob Volansky
Reference:
Tu Huakang, et al. BMJ. 2018;doi:10.1136/bmj.k134.
For more information:
Xifeng Wu, MD, PhD, can be reached at The University of Texas MD Anderson Cancer Center, 1515 Holcomb Blvd., Houston, TX 77030; email: xwumdacc@gmail.com.
Disclosure: Wu reports no relevant financial disclosures.