The major finding of the present study is a significant decrease in the mean 10-year CHD risk at 6-month follow-up and that the effects were still sustained at 18-month follow-up. The number of subjects with intermediate 10-year CHD risk (> = 10%) also decreased significantly at each follow-up time.
A previous study also showed significant change in 10-year CHD risk after lifestyle intervention. The results from the PREMIER Trial showed that, in individuals with prehypertension or stage 1 hypertension, 2 multicomponent behavioral interventions (EST + DASH and EST) significantly reduced the estimated 10-year CHD risk by 12% and 14%, respectively . The DEPLOY pilot study indicated that community-based delivery of the DPP lifestyle intervention could have a significant effect on prevention of CHD in overweight adults with abnormal glucose metabolism. At 4 and 12 months, the intervention group experienced significant decreases in 10-year risk from baseline (-3.28%, P < 0.001; and -2.23%, P = 0.037) compared with control subjects (-0.78%, P = 0.339; and +1.88%, P = 0.073) . The California WISEWOMAN Project reported that the improvement in the 10-year CHD risk was greater for an enhanced intervention group (EIG) than for a usual care group (UCG), and this improvement was significantly greater when the women’s CHD risk levels were in the upper quartile at baseline .
From the results of our study, other cardiovascular disease risk factors did not show significant results, except for weight and BMI. This may have been caused by the 10-year CHD risk reflecting the comprehensive effect of intervention. Maybe some of the cardiovascular disease risk factors changed a little, but this was still not significant. When we combined the changes in cardiovascular disease risk factors together into the 10-year CHD risk, it showed a significant change.
The present study also showed the sustainment of the effect when the intervention was stopped after 18-month follow-up. This proved that the effect of a short-term intervention can be sustained after a long-term follow-up period, greater than one year.
Similar results were also shown in other previous studies. Lindstrom et al. found that lifestyle intervention in people at high risk for type 2 diabetes resulted in sustained lifestyle changes, a modest difference in body weight change and reduction in diabetes incidence, which remained after the individual lifestyle counseling stopped . A study conducted by Elmer et al. showed that, over 18 months, persons with prehypertension and stage 1 hypertension could sustain multiple lifestyle modifications that improve control of blood pressure and could reduce the risk for chronic disease . Four-year results of the Look AHEAD Trial indicated that intensive lifestyle intervention can produce sustained weight loss and improvements in other CVD risk factors in individuals with type 2 diabetes .
The results of the present study indicated significant decrease in weight and body mass index at 6-month follow-up. In addition, the reductions were sustained and showed significantly stronger decrease at 18-month follow-up. This proved that, by implementing lifestyle intervention, weight loss can be achieved, which is similar to the results of previous studies.
In a lifestyle intervention study implemented among persons at high risk for cardiovascular disease and diabetes in a rural community, 52% of participants met the 7% weight loss goal and 66% achieved at least a 5% weight loss . However, the sample size was very small (N = 84 and N = 65, respectively). A study conducted by Lindstrom et al. in 2003 indicated that, after 1 and 3 years, weight reductions were 4.5 and 3.5 kg in the intervention group and 1.0 and 0.9 kg in the control group, respectively . In the present study, weight reduction was 1.5 kg in the intervention group and 0.6 kg in the control group after 18 months.
The present study has limitations. Firstly, our study has a non-randomized study design. The participants were allocated to either the intervention or the control group on the basis of each participant’s desire. The subjects with a strong desire to improve their lifestyle were more inclined to accept the intervention and then acquired a better effect of changes in cardiovascular disease risk and lifestyle behavior. However, since the baseline cardiovascular disease risk factors were similar in the two groups, the non-randomized study design may not affect the main significant results in the changes of cardiovascular disease risk in our study.
Secondly, the assessment of lifestyle behavior change in the study was based on a self-reported questionnaire. This may have resulted in some recall bias when evaluating the change in lifestyle behavior and have led to little significant change in lifestyle behavior between the intervention and control groups. Further study should focus on a detailed method to evaluate the change in lifestyle behavior, such as using pedometers to measure change in physical activity.
Thirdly, this study has a high drop-out rate. On the one hand, as the results showed, younger people were more inclined to withdraw from our study, maybe because they were not interested in the form of the intervention. For example, younger people may prefer to choose more vigorous exercises instead of the jogging and gymnastics done in our study. On the other hand, subjects with higher BMI, thus having higher 10-year CHD risk, were more inclined to withdraw from our study, which limited the significance of the results.
Lastly, the number of participants was relatively small, especially in the intervention group, which might have limited the significance of the results and the generalization to the middle-aged Japanese population. Regarding the generalization of this study, the intensity of intervention that targeted a large percentage of the population who are at high risk of CVD may have been too strong. In a future study, a new method of intervention of less intensity should be developed, which can be applied worldwide, considering the limited ability of health services in many areas.