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The metabolic syndrome is a clustering of non-communicable diseases (NCD) which may increase probability of developing such disorders like cardiovascular diseases, diabetes mellitus and kidney disease (1, 2). Risk of cardiovascular diseases accompanying metabolic syndrome is approximately doubled compared with absence of the syndrome (3); Moreover individuals with metabolic syndrome are at increased mortality risk of cardiovascular diseases and all other causes (2-4).
Studies have shown that lifestyle intervention reduces the risk of progression from glucose intolerance (IGT) to overt type 2 diabetes (5, 6). Furthermore, it has been shown that lifestyle modification may also decrease the prevalence of metabolic syndrome and reduce the occurrence of abdominal obesity in subjects with IGT (7). Such an effect in reducing prevalence of metabolic syndrome has been reported in a few studies in special groups (8). However, the evidence is limited regarding specific strategies that are most helpful for the long-term maintenance of lifestyle changes (9). In addition, implementation of a healthful lifestyle must expand beyond the individuals to the community scale and basically in cultural levels. Searching current literature shows that some nationwide health screening and interventions programs specifically targeting the metabolic syndrome has been designed (10), Despite the fact, the effect of lifestyle modification on management of metabolic syndrome has not been reported at the community scale yet.
The Tehran Lipid and Glucose Study (TLGS) provides a unique opportunity to begin to address these issues. It is a large scale community based prospective study performed on a representative sample of district 13 of Tehran inhabitants, the capital city of Iran. The TLGS was established with the aim of determining the prevalence of metabolic syndrome and evaluating the feasibility and effectiveness of lifestyle modification interventions in prevailing or postponing the development of the syndrome risk factors and outcomes in a population in nutrition transition (11). The baseline report of TLGS showed high prevalence of metabolic syndrome in the study population (12).
The aim of this study was to assess the effects of lifestyle modifications on metabolic syndrome and some of its components in urban population of TLGS.
Altogether 6870 subjects 4065 women and 2805 men aged 20-74 years attended in both phase of the study. They were 1755 women and 1206 men in intervention and 2310 women and 1599 men in control groups. Mean age was 43.3 ± 14.0, and 43.8 ± 14.1 years in control and intervention groups, respectively. There was no significant difference in age, sex, literacy, general and abdominal obesity, serum concentrations of lipids, glucose and insulin, HOMA-IR, physical activity, and other baseline variables between intervention and control groups (Table 1).
| Characteristic | Control (n=3909) | Intervention (n=2961) | |
|---|---|---|---|
| Male, % | 40.9 | 40.7 | |
| Literacy, % | 90.4 | 90.6 | |
| Age, year | 43.3 ± 13.9a | 43.8 ± 14.1 | |
| Marital status (% married) | 83.1 | 82.5 | |
| Daily cigarette smoker,% | 11 | 9 | |
| Body mass index, kg/m2 | 27.1 ± 4.6 | 27.1 ± 4.6 | |
| Waist circumference, cm | 88.7 ± 12.1 | 88.9 ± 12.1 | |
| Waist to hip ratio | 0.87 ± 0.08 | 0.87 ± 0.08 | |
| Systolic blood pressure, mm/Hg | 120 ± 19 | 120 ± 19 | |
| Diastolic blood pressure, mm/Hg | 78 ± 10 | 78 ± 11 | |
| Fasting serum glucose, mg/dL | 98.9 ± 34.2 | 99.3 ± 35.3 | |
| Serum insulin, mIU/L b | 7.52 ± 5.64 | 7.08 ± 5.77 | |
| HOMA-IR | 5.5 ± 4.9 | 5.2 ± 4.8 | |
| Serum cholesterol, mg/dL | 212 ± 47 | 212 ± 46 | |
| Serum triglyceride, mg/dL | 174 ± 121 | 174 ± 120 | |
| Serum LDL-C, mg/dL | 135 ± 38 | 136 ± 38 | |
| Serum HDL-C, mg/dL | 42.3 ± 10.9 | 42.3 ± 11.0 | |
| Physical activity, % | |||
| Highly active | 26.5 | 23.4 | |
| Moderately active | 18.2 | 16.2 | |
| Mildly active | 30.5 | 34.4 | |
| Not active | 24.8 | 26.0 |
There was no significant difference in the prevalence of metabolic syndrome and its components at the baseline between 2 groups (Table 2). After 3.6 years, the prevalence of metabolic syndrome increased from 37.7% to 41.2% (P < 0.001) in intervention group, and from 38.6% to 44.7% (P <0.001) in control group. The rise in the prevalence of metabolic syndrome was more prominent in control as compared to intervention group (P < 0.002 for the change between groups). The age and sex adjusted odds ratio (OR) in the intervention group compared with the control group was 0.84 (95% CI, 0.75-0.95).
| Baseline | After 3.6 years | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Int, % b, f | Contf | P value Between Groupsc | Inta | P value From Baseline to year 3.6 | Cont | P value From Baseline to year 3.6 | P value Between Groupsc | P value for Change | ||
| Metabolic syndrome | 37.7 | 38.6 | 0.39 | 41.2 | < 0.001 | 44.7 | < 0.001 | < 0.002 | < 0.001 | |
| Abdominal obesitya | 37.1 | 36.0 | 0.50 | 46.6 | < 0.001 | 48.3 | < 0.001 | < 0.014 | < 0.001 | |
| Elevated fasting glucose a | 24.6 | 24.3 | 0.89 | 23.7 | 0.28 | 29.0 | <0.001 | < 0.001 | < 0.001 | |
| Elevated triglyceridea | 49.8 | 50.3 | 0.58d | 44.7 | < 0.001 | 47.8 | < 0.002 | 0.014d | <0.001 | |
| Low HDL cholesterol a | 69.2 | 69.9 | 0.84d | 76.1 | < 0.001 | 82.2 | < 0.001 | < 0.001d | < 0.001 | |
| Elevated blood pressurea | 34.6 | 34.2 | 0.94e | 31.1 | < 0.001 | 29.5 | <0.001 | 0.25e | < 0.014 | |
The change of different components of metabolic syndrome in intervention and control groups at baseline and after 3.6 years is shown in Table 2. After 3.6 years, decrease in the prevalence of elevated blood pressure and elevated triglycerides levels occurred in both groups compared with baseline values. The prevalence of elevated fasting glucose increased in control group, but not in intervention group. The prevalence of abdominal obesity and low HDL cholesterol increased significantly in both groups after 3.6 years, as compared to baseline values.
However, comparison between groups showed that the prevalence of metabolic syndrome and 4 of its 5 components, (abdominal obesity, elevated fasting glucose, elevated triglyceride and low HDL cholesterol) were more prominent in the control group, as compared to intervention group. Comparisons showed that lifestyle intervention reduced abdominal obesity (OR 1.24, CI 1.07-1.44), elevated fasting glucose (OR 1.67, CI 1.43-1.95), elevated triglyceride (OR 1.18, CI 1.04-1.34) and low HDL cholesterol (OR 1.52, CI 1.32-1.76), adjusted for age, sex and baseline values. Changes in the prevalence of metabolic syndrome in various age groups are shown in Table 3. Although the prevalence increased in all age groups in both intervention and control subjects, the increase was less in intervention group as compared to control group in all age groups, except for subjects of 20-29 years old.
Table 4 compares changes in various parameters of metabolic syndrome in various age groups. Significantly fewer rises in percentages of abnormality in components of metabolic syndrome was obvious in all age groups in intervention subjects. Change between intervention and control groups was more evident in the frequency of elevated fasting glucose and low HDL cholesterol after 3.6 years of intervention. Percentage of elevated fasting glucose increased in all age groups in control subjects, but not in the intervention individuals, with significant decrease in the percentage of hyperglycemia in the elderly subjects.
| Baseline | After 3.6 Years | |||||||||
| Age Group, y | Int, % a | Cont c | P value Between Groups b | Int | P value From Baseline to Year 3.6 | Cont | P value From Baseline to Year 3.6 | P value Between Groups b | P value for Change | |
| 20-29 | 10.1 | 11.8 | 0.33 | 13.2 | 0.096 | 13.9 | 0.165 | 0.86 | 0.158 | |
| 30-39 | 24.7 | 22.4 | 0.87 | 28.5 | 0.08 | 32.5 | < 0.001 | 0.06 | < 0.001 | |
| 40-49 | 44.1 | 46.1 | 0.68 | 48.4 | 0.053 | 3.6 | < 0.001 | 0.08 | < 0.014 | |
| 50-59 | 57.8 | 57.1 | 0. 90 | 62.0 | 0.089 | 63.5 | < 0.001 | 0.46 | < 0.069 | |
| 60-69 | 57.3 | 60.3 | 0.54 | 58.8 | 0.672 | 64.8 | < 0.047 | 0.12 | < 0.009 | |
| ≥ 70 | 45.6 | 51.5 | 0.98 | 47.4 | 1.00 | 63.3 | < 0.035 | 0.13 | < 0.001 | |
| Age Group, y | Change Between Intervention and Control Groups a,% (P value) | ||||
|---|---|---|---|---|---|
| Abdominal Obesity b | Hypertension c | Elevated Fasting Glucose | Elevated Triglycerides d | Low HDL Cholesterol d | |
| 20-29 | -0.7 (0.357) | +1.5 (0.071) | -3.5 (< 0.001) | -4.4 (< 0.003) | -3.9 (< 0.029) |
| 30-39 | -5.3 (< 0.003) | -1.6 (0.023) | -4.6 (< 0.001) | -3.95 (< 0.001) | -4.5 (< 0.016) |
| 40-49 | -1.4 (0.245) | -3.2 (0.256) | -6.8 (< 0.011) | -3.2 (< 0.003) | -6.7 (< 0.001) |
| 50-59 | -0.1 (0.48) | +0.8 (0.441) | -10.9 (< 0.001) | -0.6 (0.359) | -11.1 (< 0.001) |
| 60-69 | -7.0 (< 0.001) | +7.4 (< 0.001) | -3.2 (< 0.001) | +0.6 (0.39) | -3.2 (< 0.074) |
| 70-74 | +1.8 (0.371) | -10.6 (< 0.001) | +1.8 (< 0.001) | -15.03 (< 0.001) | +1.8 (< 0.383) |
Dietary data did not show significant difference in energy intake and macronutrient consumption between two groups at baseline and after intervention. The within person CV was large at 32%, ranging from 30% in women to 42% in men.
Most individuals in control and intervention groups were mildly active and non active before intervention, 83% and 84%, respectively. The corresponding values were 78% and 72% (P = NS) after intervention. Chance for being less active was significantly higher in control men as compared to intervention men after 3.6 years: OR = 1.2 (1.01-1.44, P < 0.05).
Regular monitoring of drug intake for diabetes, dyslipidemia and hypertension showed that both before and after lifestyle interventions no significant difference in drug intake was seen between two groups.
In this community based intervention study we found that a 3.6 year of lifestyle intervention slowed the rise in the prevalence of metabolic syndrome and some of its components. regarding our knowledge this is the first large population based study that shows the effectiveness of lifestyle modifications in the reduction of rise in metabolic syndrome prevalence in a community.
Few studies have been conducted on lifestyle modification for reducing prevalence of metabolic syndrome. Weight loss was the most important underlying preventive mechanisms in order to lessen metabolic syndrome prevalence (5-8). Weight reduction of > 10% of initial body weight leads to greater fall in the prevalence of components of metabolic syndrome, as compared with weight loss of < 10% which induces less efficacy (18). It has been shown that the adoption of various dietary patterns may normalize the components of the metabolic syndrome (19-21), including lowering blood pressure in hypertensive patients with metabolic syndrome (22). In the present study, change in the prevalence of metabolic syndrome and 4 of its 5 components were significantly lower in intervention group as compared to control group after a 3.6 year of intervention. Although the prevalence of 2 of 5 components (abdominal obesity and low HDL cholesterol) increased in the intervention group, despite the fact, these increments were significantly smaller than those in control group. The prevalence of fasting hyperglycemia was unchanged in intervention group, after 3.6 years while the prevalence of this component increased significantly in the control group. Fall in the prevalence of elevated triglyceride was also more prominent in intervention group, as compared to control group.
Abdominal obesity and insulin resistance are the main elements of metabolic syndrome (20, 22). A change in body weight strongly correlates with an augmentation in insulin sensitivity (23). While abdominal obesity increased in both groups after 3.6 years, but the increment in intervention group was lower than that in control group. It may proposed that this difference may also contribute to higher later cardiovascular diseases risks, as abdominal obesity which correlates well with this unwanted events (24).
Lack of change in the prevalence of increased fasting glucose in the intervention group compared with its increase in the control group is significantly of importance. Recent studies have shown that lifestyle intervention reduces the risk of progression from impaired glucose tolerance to overt type 2 diabetes (6). The findings of present study is in concordance with the above findings that without intervention the prevalence of fasting hyperglycemia increases, but popularization of this concept to a community scale, shows that lifestyle intervention in general population could also reduce the risk of rise in fasting glucose.
Rise in the percentages of abnormalities in many components of metabolic syndrome was less prominent in both gender and all age groups. This important finding points to the parallel effectiveness of lifestyle interventions in all members of the study population.
All recommendations for clinical management of the metabolic syndrome can be summarized in lifestyle changes, healthy diets and more exercises, at first-line interventions and consequently drug therapy when necessary, along with strategies for cardiovascular diseases prevention (7, 25, 26). The ATP III, in its update, states that “in those with the metabolic syndrome, individualized counseling for weight loss, regular exercise, and therapeutic diet may be particularly effective in helping to improve plasma triglyceride and HDL cholesterol values while offering promise to reducing the burden of medication required to improve the risk factor profile” (27). However, most current health providing systems in various countries do not provide tools or supports to properly initiate lifestyle changes; for example, workplaces, social and cultural systems do not provide opportunities or facilities for increasing physical activities compliance among people.
It is well documented that physical activity has several beneficial effects on most components of metabolic syndrome including elevated blood pressure, central obesity and insulin resistance (22, 23, 28). This may due to a direct effect or an effect resulted from promoting weight reduction (29, 30). Changes in physical activity have been added to healthcare instructions in most therapeutic interventions for preventing promotion of metabolic syndrome (22, 29). However, it is believed that dietary changes are considered as the core strategy of the management, with weight reduction playing as a key role and moreover exercise having an additional favorable effect. In the present study, small difference in physical activity was only seen in men after intervention; however, Lipid Research Clinic questionnaire which was employed in this study is a crude tool for the assessment, while other quantities instruments might have shown more changes.
Attention to behavioral factors including cognitive readiness and psychological parameters that might influence individual’s ability to reach lifestyle ideals helps people to adhere to multifaceted and demanding lifestyle modifications. Context of behavioral intervention may include goal setting, self-monitoring, problem-solving, Control of stress stimulus, management of high-risk situations and relapse prevention (31).
In a recent review, Fappa et al. evaluated the effectiveness of lifestyle intervention by critically exploring patients adherence to the recommendations, in 6 randomized and one non-randomized controlled trials and 5 without control group intervention trials, they found that greater adherence was correlated with greater improvements in the components of metabolic syndrome (32). However, the evidence was limited regarding respective approach to specific behavioral or motivational factors in helping patients to adhere to the multifaceted lifestyle changes.
The present study has a few limitations. Nutritional data before and after intervention collected only in a few individuals and did not show significant changes after intervention. It is north worthy that total calorie and nutrients intake in free-living persons differs from day to day and seasonally (33, 34). The within-person CV in our population proved to be large that tends to be similar in studies in India and China (35). Measurements of dietary intake based on small numbers of 24-h DRs per subject may provide a reasonable mean estimate for a group, but the standard deviation will be greatly over-estimated (33). Such information directly influences the detection of differences between treatment and control groups in experimental or interventional studies. We used Lipid Research Clinic questionnaire for baseline measurements of physical activity; however, the results were not conclusive and the questionnaire was considered not to be appropriate for TLGS population (12). The strength of this study is a well controlled intervention at the community level with a large number of participants who completed 3.6 years of follow up. The novelty of the work resides in demonstrating the effectiveness and efficiency of the style of intervention used in terms of real life in the community.
In conclusion, comprehensive life style modification could prevent the rise in the prevalence of metabolic syndrome at the community level. The intervention is effective in reducing or halting abnormalities in all components of metabolic syndrome and particularly in elevated fasting glucose and low HDL cholesterol. It is of outmost interest to study outcomes of cardiovascular and other non-communicable diseases after longtime community life style modification.
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