Kuopio, Finland - Results from a recent Finnish trial have shown that aerobic physical exercise did not halt the progression of atherosclerosis in a population of middle-aged men. Physical activity also failed to statistically lower C-reactive protein (CRP) compared with a control group of nonexercising subjects, report investigators.
Despite that the results failed to show that regular exercise slowed the progression of atherosclerosis and lowered CRP, the authors report the benefit of aerobic physical activity did extend to subjects not taking statins.
"In the majority of the participant population, we saw a significant reducing effect of exercise both on atherosclerosis and CRP," Dr Rainer Rauramaa (Kuopio Research Institute of Exercise Medicine, Kuopio, Finland) told heartwire. "In the population at large, the vast majority of people are not using statins, even if they are increasingly used for patients suffering from coronary heart disease and diabetes. Therefore, clinicians should pay more attention to motivate people to engage more in regular exercise. This type of exercise is safe, does not carry any serious side effects, and is an efficient and economic way to prevent atherosclerosis."
The results of the study are published in the June 15, 2004 issue of the Annals of Internal Medicine.
Subgroup analysis yielded positive results
Investigating the effects of regular long-term physical exercise on chronic low-grade inflammation and the progression of atherosclerosis, the investigators studied middle-aged men randomly selected from the population registry of the DNA Polymorphism and Carotid Atherosclerosis (DNASCO) trial. The primary end point of the study was the progression of mean intima-media thickness (IMT) of the carotid artery.
In total, 70 men were assigned to an exercise program and 70 subjects to the control group. The men in the exercise group were prescribed walking, jogging, cross-country skiing, swimming, and cycling as the main methods of aerobic exercise. During the first three months, the men were advised to exercise three times per week for 30 to 45 minutes, and this was later increased to five times per week for 45 to 60 minutes per session for the remainder of the trial.
Exercise intensity was determined individually and modified when necessary to correspond to 40% to 60% of maximal oxygen uptake. The men were given heart-rate monitors to help them adhere to the prescribed training rate. Subjects in the control group were allowed to choose whether to engage in an exercise program, but no efforts were made to modify their physical activity.
At the time of randomization, the mean CRP level was 16.1 nmol/L in the exercise group and 15.2 nmol/L in the control group. During the intervention, CRP remained consistently lower in the subjects randomized to the exercise program, but the difference was not statistically significant. At randomization, mean IMT of the carotid bifurcation was 1.12 mm in the exercise group and 1.05 mm in the control group. The progression of IMT in the carotid artery did not differ between the two study arms.
However, a subgroup analysis that excluded 15 patients taking statins showed that the six-year progression of IMT was 40% less in the subjects assigned to the exercise program than those in the control group (p=0.02). In this analysis, atherosclerotic progression leveled off in the exercise group after three years of intervention but continued in a linear fashion in the control group.
"Statins have a powerful antiatherosclerotic effect and there were more patients on statins in the reference group than in the exercise group," said Rauramaa. "This could be the reason that the results turned statistically significant only when statin users were excluded. Our results will not change anything in patient care, except that physicians should encourage their patients to engage in regular exercise, whether or not they are taking statins."
The authors point out that the study is limited in that it included only middle-aged white men. Also, as sample-size estimates were based on changes in IMT and not other end points, the study was small and underpowered to detect changes in CRP levels. At their lab in Finland, Rauramaa said, they are currently conducting a four-year randomized controlled trial known as the Dose Responses to Exercise Training (DR's EXTRA). In this 1800-person trial, investigators are studying the effects of exercise on inflammation, endothelial function, and atherosclerosis.