The Influence of Walking at Different Times of Day on Blood Lipids and Inflammatory Markers

Overview

It has been well known that moderate and regular levels of physical activity has a favorable effect on many of the established risk factors related to coronary artery disease (CAD). Given that exercise in the morning has a greater potential for inducing sudden cardiac death and myocardial ischemia, it may be sensible for patients with CAD not to take exercise at this time. Our previous study indicated that the protective effect of exercise in the evening was greater than morning. However, which times of day to exercise could achieve the greatest improvements in lipids and inflammatory markers remains unclear. The purpose of the present study was to investigate the responses of lipid profiles and inflammatory markers to walking at different times of day in sedentary patients with CAD.

According to the inclusion and exclusion criteria, 330 patients with CAD between the ages of 40 and 80 years were recruited from the inpatient cardiology department of the First Affiliated Hospital of Nanjing Medical University. Informed consent was obtained from each participant after explaining the study protocols. Patients were randomly assigned to one of the three groups: control group (n=110), morning walking group (n=110) or evening walking group (n=110). The control group was requested to maintain their usual level of physical activity. Participants in both walking groups were requested to walk at the speed of 2.5 miles/h for 30 min/day or more on at least 5 days/week for a period of 12 weeks. The protocol of exercise was identical, while the difference between the two groups was that one group was asked for walking in the morning and the other group walking in the evening. Each participant was telephoned at least once a week to ensure the adherence to the exercise program. Patients were called back every month to understand the information about walking and medication use. In the intervention groups, subjects whose compliance rate with their respectively walking program were less than 85% were excluded in the analysis. Additionally, all the participants were given an advice on quitting smoking and were provided with similar diets by a nutritionist, as to caloric intake and nutrients. Total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, lipoprotein a, white blood cell count and platelet count, fibrinogen were measured before and after the intervention. The Kolmogorov-Smirnov test was used to check the normal distribution of all continuous variables. The values of normal distribution were expressed as mean±SD, and non-normal distribution data were presented as median (interquartile range). Baseline differences between groups were determined by one-way analysis of variance and chi-square analyses. Baseline and follow-up values within each group were compared using the paired t test. General linear models were used to adjust the differences in baseline values for dependent variables. And two-way ANOVA was used for determination of the improvements of lipids and inflammatory markers in three groups. The significance level was defined as P\<0.05. All analyses were carried out using SPSS version 13.