Prevalence of Metabolic Syndrome in a Large Integrated Health Care System in North Carolina

Discussion

The current study determined the prevalence of MetS in a large health care system in North Carolina and assessed the association between demographic characteristics and MetS. This study is one of very few to have investigated the prevalence of MetS for a specific region in the United States. Also, to the best of our knowledge, this is the first study determining the prevalence of MetS in North Carolina.

The crude prevalence of MetS was 22.5%. This finding is similar to the crude prevalence of 23% reported by Hivert and colleagues in their study of patients receiving care at 12 outpatient health care practices in Massachusetts during 2003–2004 [8]. However, we found an age-standardized prevalence of MetS of 18.8%, which was lower than the most recent national estimate of 22.9% based on the 2009–2010 NHANES data [11]. The likely reason for the lower age-standardized MetS prevalence in our study is the use of surrogate criteria for MetS, which have a sensitivity of 73% compared to the formal criteria for this condition.

In terms of individual criteria, the major factors contributing to MetS were elevated BMI (crude proportion of 54.1% and age-standardized proportion of 51.4%) and elevated blood pressure (crude proportion of 60.9% and age-standardized proportion of 49.5%). This finding is similar to that found by Hivert and colleagues in their study of patients in Massachusetts. However, in a study examining the national prevalence of MetS, Beltrán-Sánchez and colleagues found that increased waist circumference and elevated cholesterol levels were the criteria with the highest prevalence.

Interesting findings emerged from the logistic regression analysis conducted to examine the association between demographic factors and MetS. Patients aged 30–39 years and those aged 70–79 years were more likely to have MetS, and those aged 18–29 years were less likely to have MetS, compared to patients aged 80 years and older. MetS prevalence increased with age until the 6th decade and then decreased in the 7th and 8th decades of life. Increasing MetS prevalence with age has been reported in previous research [4, 8, 13]. The lower MetS prevalence among those in the 7th and 8th decades of life might be due to survival bias of individuals with better health in these age groups.

Women were 7% more likely to have MetS compared to men. The main criteria contributing to higher prevalence of MetS among women were elevated BMI (58.2% in women versus 49.0% in men) and elevated cholesterol levels (34.8% in women versus 23.6% in men). Factors such as weight gain after pregnancy, gestational diabetes mellitus, preeclampsia, polycystic ovary syndrome, use of hormonal contraceptives, and menopause increase the odds of females having MetS [14].

In terms of race and ethnicity, Hispanic individuals were 14% more likely to have MetS compared with non-Hispanic whites. This finding is consistent with previous research [4] and could be associated with the high prevalence of insulin resistance, the high prevalence of diabetes mellitus, and the propensity for elevated triglyceride levels in the Hispanic population [13].

In our study, patients with Medicaid and Medicare were more likely to have MetS compared with those who had commercial insurance. Previous work has shown that having less access to health care and limited family and community resources is associated with poorer health outcomes and more chronic health conditions in the Medicaid population [15, 16]; this trend was also seen in our study. Medicare beneficiaries include individuals above 65 years of age, individuals with disabilities, those with end-stage renal disease, and patients with amyotrophic lateral sclerosis. It is not surprising to see a higher prevalence of MetS in these individuals, as they have been found to have worse health status compared to those with private health insurance [17]. To the best of our knowledge, this is the first study determining the association between insurance status and MetS.

The findings of this study have important implications for health care providers and policy makers in North Carolina. Finding that 22.5% of patients in the largest health care system in North Carolina have MetS suggests that the burden of this condition in North Carolina could be significant. North Carolina is currently among the quartile of US states with the highest prevalence proportions of diabetes and cardiovascular disease [18]. The Healthy North Carolina 2020 objectives include reducing diabetes prevalence and cardiovascular mortality rates [19]. Reducing the burden of MetS will be important for achieving these goals. Prior studies have found that MetS can be effectively managed with lifestyle interventions—such as counseling about diet modifications and physical exercise by family physicians, nurses, and dieticians, which target all the MetS components together—as well as pharmacological treatments targeting individual MetS components [20-22]. The associations observed in this study between demographic characteristics and MetS and its components could help policy makers in North Carolina to select targets for such interventions. The MetS prevalence estimates observed in this study could also be used as a baseline for judging the effectiveness of future interventions.

Issuing clear guidelines concerning the screening of patients for MetS would also further efforts to address the high prevalence of this condition. Japan has led the way in the development of such guidelines by recommending since 2008 that annual MetS screening be performed for individuals aged 40–74 years [23]. Currently, there are no specific guidelines regarding screening for MetS in clinical practice in the United States, and variations in the recommended ages and time intervals between tests for individual components of MetS (blood pressure, blood glucose, and lipids) could result in missed opportunities to identify patients with this condition.

This research has a few limitations. Collection of study data from an EMR system could have affected these results due to potential mistakes in data entry. Carolinas HealthCare System's facilities are mainly in Western North Carolina; therefore, the MetS prevalence proportions observed in this study may not be generalized to the entire state. We excluded cases without data for all 5 MetS parameters, which reduced the size of the base population and could have biased our results. The direction and magnitude of such bias is difficult to predict. For example, some healthier and/or younger patients without MetS may not regularly visit health care providers and/or have routine blood work performed. Such patients would have been excluded from our study, thus increasing the MetS prevalence estimates. On the other hand, some patients with MetS might have had only a few laboratory values measured during the study year. These patients also would have been excluded from our analysis, decreasing the MetS prevalence proportions. The use of surrogate criteria to examine the presence of MetS could have underestimated the actual MetS prevalence. Finally, we determined the insurance status of the study cohort based on the primary payer listed on the most recent billing record prior to collection of laboratory measurements. Using this process, we could not take into account changes in insurance status or the presence of multiple insurance policies. The findings of the study should be interpreted in light of these limitations.