M. Halldin U de Faire M-L Hellénius

M Halldin1, U de Faire1,2, and M-L Hellénius3,4, 1Department of Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institute, 2Cardiovascular Laboratory, Department of Cardiology, Karolinska University Hospital Solna, 3Center for Family and Community Medicine, Karolinska Institute, 4Department of Medicine, Karolinska University Hospital Solna, Karolinska Institute, Stockholm, Sweden There is today a great interest in the role of the metabolic syndrome in the pathogenesis of cardiovascular disease, type 2 diabetes, and common cancers [1-3]. Many publications report an alarmingly high prevalence of the metabolic syndrome in different populations [4]. In a recently published study on the associations between lifestyle factors and the metabolic syndrome we made use of the complete population registry in Sweden and invited every third 60-year-old man and woman (n 5,460) in Stockholm County to a thorough health examination [5]. The response rate was high (77%) and 2,036 men and 2,192 women participated and underwent a physical examination and filled in an extensive questionnaire. The total prevalence of the metabolic syndrome was, according to the NCEP III definition [6], 26% and 19% in men and women, respectively.

Strong Dose-Response Relationship between Physical Activity and the Metabolic Syndrome

We noted a strong inverse dose-response relationship between reported physical activity (PA) levels in leisure time and the prevalence of the metabolic syndrome. The odds ratio (OR) for having the metabolic syndrome in the high leisure time PA group was 0.33 (95% confidence interval (CI), 0.22-0.51) using the low leisure-time PA group as a reference. Interestingly, and most important we think, is the fact that this association was unaffected after adjustment for other relevant factors as sex, marital status, education, smoking, dietary habits, and alcohol consumption, OR 0.33 (95% CI, 0.22-0.51). The majority of both men and women were still fulltime employed (72% of the men and 64% of the women). However, we did not find any association between work-related physical activity and the metabolic syndrome. This is probably due to the fact that men and women of that age and living in an urban or semi-urban area of Sweden usually have sedentary jobs, while regarding the leisure-time PA there is a large span between sedentary individuals and highly active individuals. Therefore the association between PA in leisure time and the metabolic syndrome is more easily detected.

Our data indicate that PA might reduce the prevalence of the metabolic syndrome by almost 70%. The men and women in the high leisure-time PA group (n 302, 8%) reported a high intensive PA (activities that make you sweat, e.g. aerobics, running, tennis, or other strain exercise) more than 2 times a week and at least 30 minutes each time. The individuals in the reference group (n 466, 12%) reported a sedentary lifestyle with less than 2 hours of low intensive (without sweating) PA/week. Notable is also the fact that individuals engaged in light PA (n 2,340, 58%), reporting activities without sweating (e.g. walking, cycling, gardening) at least 2 hours/week, also had a significantly and substantially reduced risk of the metabolic syndrome, adjusted OR 0.50 (95% CI, 0.40-0.64) compared to the reference group. For men and women in the moderate activity group (n 939, 23%) reporting regular moderate intensity activities 1-2 times/week at least 30 minutes each time, the OR was 0.43 (95% CI, 0.32-0.58).

More Is Better Than Little, But Little Is Better Than Nothing

The results are in accordance with other cross-sectional studies as well as prospective studies demonstrating an inverse association between level of PA (or fitness) and the occurrence of the metabolic syndrome [7-9]. The results are also in agreement with a recent randomized controlled study regarding the effects of different doses of physical activity on cardiorespiratory fitness in sedentary overweight or obese postmenopausal women. A graded dose-response change in fitness across levels of exercise training was demonstrated. One striking finding was that even a small increase in activity, corresponding to an energy expenditure of 4 kcal/kg/week, or approximately 70 minutes/week, which means half of the recommended dose in current guidelines and recommendations, was associated with a significant increase in fitness [10].

Physical Inactivity ─ A Powerful Risk Factor

In the light of many international reports regarding the sedentary lifestyle in several different populations, our findings are important. In the USA, as well as in Sweden, only a minority (approximately 20%) of the population meet the criteria for a physically active lifestyle, e.g. engaged in at least 30 minutes of moderate intensity PA on most, preferably all, days of the week [11-13]. Consequently, the majority of populations today are physically inactive and physical inactivity is today by the World Health Organisation listed as one of the ten most powerful health risks [14]. We are facing a worldwide epidemic of a sedentary lifestyle and increasing body weight, especially abdominal obesity. Data from Sweden and the United Kingdom demonstrate that the relative increase in waist circumference, compared to the increase in BMI, during the last decades is larger. This is true for both adult men and women, as well as for children [15-17]. Abdominal obesity is, together with the insulin resistant state in the skeletal muscle, strongly associated with physical inactivity and the metabolic syndrome [1].

In parallel with the increasing evidence from epidemiological studies regarding the relationship between physical activity and the metabolic syndrome, there is also increasing knowledge about underlying mechanisms. The multiple effects from increased physical activity on factors like body weight, abdominal obesity, fat distribution, insulin resistance, lipoprotein metabolism, blood pressure, endothelial function, fibrinolysis, and inflammation, makes physical activity a “drug of choice” in the prevention and treatment of the metabolic syndrome [18].

Time to Move from Science to Practice

To counteract the worldwide epidemic of the metabolic syndrome and the increased risk of non-communicable major diseases like cardiovascular disease, type 2 diabetes, and common cancers it is important to increase the knowledge among all health care professionals regarding physical activity and health, as well as how to promote physical activity. A recent systematic review from the Swedish Council on Technology assessment in Health Care concludes from 79 studies that it is effective to give advice and support to increase physical activity in health care [19]. One feasible way is “physical activity on prescription,” that has been used in, for example, Sweden and New Zealand for decades [20].

We conclude that the current knowledge indicates the role of physical activity in the prevention and treatment of the metabolic syndrome and that there is an urgent need to move from science and writing guidelines and recommendations to clinical practice.

References

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