Saturday, 15th June 2024

Cancers

It is well known that a number of cancers are less common in those who are physically active and also that a number of cancers carry a better  prognosis for the more physically active. The main forms of cancer which can be prevented by exercise and high level of physical fitness are those of breast, lung, and colon.

The level of protection for men

A large Swedish study of the relationship between deaths from cancer and cardio-respiratory fitness (CRF) was published last year. 177,709 Swedish men, average age 42, were exercise tested and then followed for nearly ten years. The men were divided into four fitness groups – high, moderate, low and very low. The risks of dying from several cancers in each of the three higher fitness groups were compared to that in the very low groups.

Compared to the very low fitness group, the high fitness group had 63% the risk dying from colon cancer, 29% the risk for prostate cancer and 41% for lung cancer. The risk for cancer deaths in each group was related to level of fitness. These are very large effects which indicate an important and significant cancer-protection effect from keeping fit. Those at high risk, particularly for prostate cancer (the main risk factor is a family history), should make regular exercise a priority.

The level of pr0tection for women

Physical activity is known to be modestly protective against post-menopausal breast cancer. It has not been so certain for pre-menopausal risk. Now a study of about half a million pre-menopausal women has found that those in the top 10% of leisure time physical activity had a 10% lower incidence of breast cancer that the lowest 10%.

Which exercise?

A new study of the effects of short bursts of activity has indicated that 4 to 5 minutes of vigorous activity daily can reduce cancer risk by up to 32% – including lung, kidney, bladder and stomach cancers. The study participants had an average age of 62 and had reported that they did not exercise in their spare time. Their unrecognised episodic exercise was detected from wearing a wrist accelerometer for seven days at the beginning of the study. They were then followed up for seven years to reveal these findings..

What is the connection

The relationship between exercise and cancer protection is far from simple. The best established cancers involved include breast, colon, bladder, uterus, kidney and stomach. Some investigations have indicated a dose-response relationship – ie higher doses of exercise have a greater effect in reducing cancer risk. An example is breast cancer which in one study showed a 6% risk reduction with 2.5 hours of physical activity per week and 10% risk reduction at 5 hours per week.

How does exercise give this protection?

Exercise habit does not exist in a vacuum. Highly active people tend to be of higher socioeconomic status, leaner and have generally healthier lifestyles than sedentary people. Body weight is also  a big confounder. However the apparent protection provided by exercise remains even after the figures are adjusted for differences in body weight.

In the case of breast cancer, one contribution may be from changes in female hormones from taking exercise. In other cancers the known anti-inflammatory effects of physical activity is probably a factor.

For most cases the mechanism is not well understood – which is not surprising given the range of biochemical changes brought about by exercise.

What about exercise in the management of cancer?

There is a growing interest in cancer “pre-habilitation”. This is the use of physical training to prepare cancer patients for surgery, chemotherapy and other treatments. The idea is that the fitter the patient before such treatments, the more he/she is equipped to withstand them and the faster the recovery. A meta-analysis has found that in the case of a number of different cancers, higher pre-operative fitness is associated with less postoperative complications. The best evidence for the benefits of rehabilitation for cancer is for those with lung cancer. In some cases it is only pre-habilitation which has made the patient fit enough for surgery in those who, before pre-habilitation are “functionally inoperable”.

2 responses to “Cancers”

  1. Patric Hinde says:

    I am still following reading your blogs which are extremely illuminating. 

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