Physical activity in relation to cardiac risk markers in secondary prevention of coronary artery disease

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Abstract

Background

The relationship between physical activity and cardiac risk markers in secondary prevention for patients with coronary artery disease (CAD) is uncertain. The aims of the study were therefore to examine the level of physical activity in patients with CAD, and to investigate the association between physical activity and cardiac risk markers.

Methods

In total, 332 patients, mean age, 65 ± 9.1 years, diagnosed with CAD at a university hospital were included in the study 6 months after their cardiac event. Physical activity was measured with a pedometer (steps/day) and two questionnaires. Investigation of cardiac risk markers included serum lipids, oral glucose-tolerance test, twenty-four hour blood pressure and heart rate monitoring, smoking, body-mass index (BMI), waist–hip ratio, and muscle endurance. The study had a cross-sectional design.

Results

The patients performed a median of 7027 steps/day. After adjustment for confounders, statistically significant correlations between steps/day and risk markers were found with regard to; high-density lipoprotein cholesterol (HDL-C) (r = 0.19, p < 0.001), muscle endurance measures (r ranging from 0.19 to 0.25, p = 0.001 or less) triglycerides (r =  0.19, p < 0.001), glucose-tolerance (r =  0.23, p < 0.001), BMI (r =  0.21, p < 0.001), 24-h heart rate recording during night (r =  0.17, p = 0.004), and average 24-h heart rate (r =  0.13, p = 0.02).

Conclusions

A relatively high level of physical activity was found among patients with CAD. There was a weak, but significant, association between pedometer steps/day and HDL-C, muscle endurance, triglycerides, glucose-tolerance, BMI and 24-h heart rate, indicating potential positive effects of physical activity on these parameters. However, before clinical implications can be formed, more confirmatory data are needed.

Introduction

Cardiovascular diseases, including coronary artery disease (CAD), are the most common causes of death globally and are projected to remain so [1].

Coronary artery disease is preventable, and potentially modifiable risk factors have been associated with more than 90% of the risk of a myocardial infarction in a large international case–control study [2]. Patients who have survived an acute coronary event are at increased risk for a subsequent event and are therefore of highest priority for secondary prevention [3]. Secondary prevention through exercise-based cardiac rehabilitation is an intervention with strong scientific evidence to decrease morbidity and mortality in patients with CAD [4], [5], [6]. Furthermore, exercise-based cardiac rehabilitation has favourable effects on risk markers for atherosclerotic disease [6].

The benefits associated with physical activity in primary prevention of CAD are well established and a recent meta-analysis has confirmed a graded, inverse relationship between physical activity levels and risk of CAD [7]. The effects of physical activity in relation to cardiac risk markers in secondary prevention after a coronary event are however still to be explored.

Related to this discussion, it is worth noting the theoretical distinction between physical activity and exercise. These terms are often used interchangeably, although physical activity is defined as “any bodily movement, produced by skeletal muscles that result in energy expenditure”, while exercise is defined as “a subset of physical activity that is planned, structured, repetitive, and purposeful in the sense that improvement or maintenance of physical fitness is the objective” [8].

There is limited data regarding the level of physical activity in populations of patients with CAD. The difficulty associated with providing a valid measurement of physical activity is well known. It has therefore been suggested that physical activity data would best be interpreted by adopting combinations of objective and subjective measurement approaches [9]. The pedometer is one recognized option to measure physical activity [9]. To meet current guidelines for physical activity in primary prevention, i.e. performing moderate-intensity physical activity of at least 150 min/week [10], individuals are encouraged to walk a minimum of 3000 steps in 30 min, 5 days a week [11]. Three shorter sessions of 1000 steps in 10 min, 5 days a week can also be used to meet the recommended goal. This corresponds to an energy expenditure of 1000 kcal/week. Other studies have suggested that > 7000 steps/day is recommended for further health benefits and > 10,000 steps/day for weight loss [10].

The strong evidence of the benefits of exercise-based cardiac rehabilitation is confirmed. However, the relationship between level of physical activity and cardiac risk markers in secondary prevention for patients with CAD has yet to be quantified. The aims of this study were 1) to describe the level of physical activity in patients with CAD, 6 months after the cardiac event and 2) to investigate the association between physical activity and cardiac risk markers.

Section snippets

Patient population

In total, 332 patients (75 women; mean age 65 ± 9.1 years), who were hospitalised at Sahlgrenska University Hospital/Sahlgrenska, Gothenburg, Sweden with a main diagnosis of CAD, were recruited between 2007 and 2009. The patients were included a median of 6 months (range 3–10) after hospital discharge, at end of conventional care. The inclusion criterion was a principal diagnosis of CAD, confirmed by coronary angiography, either prior to or at the time of hospitalisation. The exclusion criteria

Patient characteristics

In general, less physically active patients were older, had a longer duration of CAD, and were more likely to have a previous history of diabetes. Furthermore these patients more frequently experienced heart failure and/or atrial fibrillation as a complication at hospital. The majority of the patients were on beta-blockers and lipid-lowering drugs. The use of antihypertensive drugs, and diuretics were higher among the sedentary patients, whereas the opposite was found for statins (Table 1).

Pedometer

The

Discussion

This study demonstrated weak, but significant, associations between pedometer steps/day and HDL-C, muscle endurance, triglycerides, glucose-tolerance, BMI and 24-h heart rate in patients with CAD, indicating the possibility of positive effects of physical activity on these parameters.

Up to date physical activity in secondary prevention is often considered an exercise intervention. The data available, deals almost exclusively with physical fitness measurements and not with evaluation of physical

Acknowledgements

The authors want to thank Lillemor Stensdotter and Susanna Wittboldt for help with data collection. This study was supported by grants from the Swedish Heart and Lung Association, Rehabilitation Research Foundation, Allied Health Professions within Cardiology, Renée Eander's Foundation, the Memorial Foundation, and government grants under the ALF-agreement. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of

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    All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

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