Exercise linked to reduced risk of several cancers

Physical activity has been associated with lower risk of heart disease and all cause mortality, but its association with risk of cancer is not well understood.

Moore et al research published in JAMA Internal Medicine, suggests that exercise is a powerful cancer-preventive and found that physical activity drove down the rates of a broad array of cancers even among smokers, former smokers, the overweight and obese.

Researchers collected data from 12 prospective studies from the United States and Europe and analyzed associations between self-reported physical activities with the incidence of 26 types of cancer in the study period, which lasted 11 years between 1987 and 2004.

A total of 1.44 million participants (median [range] age, 59 [19-98] years; 57% female) and 186 932 cancers were included. High versus low levels of physical activity were associated with lower risk of 13 cancers: esophageal adenocarcinoma, liver, lung, kidney, gastric, endometrial, myeloid leukemia, myeloma, colon, head and neck, rectal, bladder, and breast. The data indicated that a higher level of activity was tied to a 7 percent lower risk of developing any type of cancer. Individuals who were very active had a 20% lower risk of cancers of the esophagus, lung, kidney, stomach, endometrium compared with people who were less active.  The reduction was slightly lower for colon, bladder, and breast cancers.

Body mass index adjustment modestly attenuated associations for several cancers, but 10 of 13 inverse associations remained statistically significant after this adjustment. Leisure-time physical activity was associated with higher risks of malignant melanoma and prostate cancer.  Associations were generally similar between overweight/obese and normal-weight individuals. Smoking status modified the association for lung cancer but not other smoking-related cancers.

Health care professionals should emphasize that physical activity was associated with lower risks of many cancer types and most of these associations were evident regardless of body size or smoking history.

One-third of all cancers maybe inherited

Muci et al published in JAMA the results of a trial that suggests that approximately one-third of all cancers are due to inherited genes. 

The investigators looked at data from 80 309 monozygotic and 123 382 same-sex dizygotic twin individuals (N = 203 691) within the population-based registers of Denmark, Finland, Norway, and Sweden, who were part of the Nordic Twin Study of Cancer. 

Twins were followed up a median of 32 years between 1943 and 2010. There were 50 990 individuals who died of any cause, and 3804 who emigrated and were lost to follow-up.

The main outcome was incident cancer and time-to-event analyses were used to estimate familial risk.

A total of 27 156 incident cancers were diagnosed in 23 980 individuals, translating to a cumulative incidence of 32%. Cancer was diagnosed in both twins among 1383 monozygotic (2766 individuals) and 1933 dizygotic (2866 individuals) pairs. Of these, 38% of monozygotic and 26% of dizygotic pairs were diagnosed with the same cancer type.

The analysis of data found that overall heritability for cancer was 33 percent among the entire study population, and significantly higher for certain types of cancers.  Significant heritability was found in 58 percent of diagnosed skin melanomas, 57 percent of prostate cancers, 43 percent of non-melanoma skin cancers, 39 percent of ovarian cancers, 38 percent of kidney cancers, 31 percent of breast cancers and 27 percent of uterine cancers.  In the same study researchers identified a set of cancers in which genetics play a very small role. This group includes lung cancer (18 percent), colon cancer (15 percent), rectal cancer (14 percent), and head and neck cancer (9 percent).”

In this long-term follow-up study among Nordic twins, there was significant familial risk for cancer overall and for specific types of cancer.  This information about hereditary risks of cancers may be helpful in patient education and cancer risk counseling.