MetS is a common medical condition and one of the common comorbidities of COPD. There is ample epidemiological and clinical evidence to support an important association between pulmonary dysfunction and MetS, but the exact nature of this association is still unknown and further studies are needed. Therefore, this study aimed to determine the prevalence of MetS in COPD patients in comparison with Non-COPD individuals in a population aged 35–75 years from Shahrekord Cohort Study.
In our study, out of 6961 participants, 30.9% had MetS. The highest prevalence MetS was observed in the age group above 55 years, women, low level of education, living in urban areas, and those with BMI over 25.
In the present study, the mean age of COPD patients was significantly higher than those without COPD. Most patients were male (55.8 %). In this study, there was no significant difference between the mean components of MetS with the exception of SBP, DBP, WC in individuals with and without COPD. The prevalence of MetS in patients with COPD was 28.4%. The difference in the prevalence of MetS between patients with and without COPD was small. In fact, we did not see a statistically significant difference in the prevalence of MetS in people with COPD without COPD. This may be because the general population includes people without COPD but with other comorbidities. In the study of Choi et al., among 2164 patients with COPD in Korea in 2007–2012, the prevalence of MetS was 31.2 % and was significantly higher in women than in men (35.1% VS 26.6%) . In one meta-analysis study of 4,208 patients with COPD from 19 studies, the pooled Prevalence of MetS in patients was 34%, and significantly higher than that in the control group (32% vs. 30%). Hypertension, abdominal obesity, and hyperglycemia were the most common parameters of MetS in patients in this meta-analysis . Verma et al. reported the prevalence of MetS in COPD patients as 15.7% .
In this study, MetS parameters were examined one by one. There was no statistically significant difference in the components of MetS except for HBP and high FBS between two groups of people with and without COPD. HBP levels and high FBS were significantly higher in patients than in healthy individuals (P < 0.05), but these differences were not significant when analyzed by gender. There was no significant difference between low HDL-c levels between patients and healthy people, but when analyzed by gender, this difference was significant in women, so that in women patients, low HDL-c levels were significantly higher than healthy women. The most common component of MetS in people with COPD was low HDL-c, WC, and High FBS. In male patients, the most common component was low HDL-c, high TG, and high FBS, and in female patients, WC, high FBS, and low HDL-c was the most common MetS component. In general, the prevalence of MetS components in people without COPD was higher than in people with COPD, which is why the prevalence of MetS in COPD patients was lower than in people without COPD (28.4% VS 31%), which was inconsistent with the results of other studies. In the study of Bermudez et al. in Philippines in 2017–2018, consistent with our findings, MetS was not associated with airflow obstruction, and among the MetS components, only HBP was associated with airflow obstruction . In a case-control study conducted by Singh et al at the chest clinic of a tertiary teaching care teaching hospital in North India in 2018, the prevalence of MetS was significantly higher in COPD patients (49.3%) than in control subjects (29.9%), which was not consistent with the results of our study. In this study, in analyzing the relationship between individual components of MetS, the authors found that serum TG, SBP, and DBP were significantly higher in COPD than in apparently healthy individuals; however, HDL-c was significantly lower in COPD patients than in the control group, which is highly consistent with our study results . A case study by Naseem et al in 2019 in northern India showed that MetS was common comorbidity, especially in mild to moderate forms of COPD. Among the components of MetS, WC, FBS, high TG levels, SBP and DBP were significantly higher in patients with MetS (P < 0.001) . In prospective study by El-toney and colleagues on 70 patients with stable COPD at the chest clinic of Cardiothoracic Minia University Hospital during 2016–2016, 44% of patients with COPD had MetS. In this study, DBP, TG, and FBS were significantly higher in patients with COPD with MetS than in patients without MetS, while HDL-c was significantly higher in patients with COPD without MetS .
In this study, we did not observe statistically significant differences in the prevalence of MetS in different stages of GOLD, which was similar to the results of other studies [7, 14, 25]. The frequency of MetS based on GOLD (I-IV) stages was 31 (50.8%), 24 (39.3 %), 6 (9.8 %) and 0.0%, respectively. The results of an cross-sectional study in southern India in 2020 showed that 54% of patients with COPD, especially in stage II and III, have MetS .
In our study, there was a statistically significant difference between respiratory symptoms and MetS. In cross-sectional study of Park and Larson in the United States in 2007–2010, respiratory symptoms were significantly higher in people with MetS than in those without MetS, which was consistent with the results of our study . Diez-Manglano et al. reported in a cross-sectional, multicenter study in 2014 that people with MetS have more shortness of breath than people without MetS . In the present study, the mean pulmonary function parameters were significantly lower in patients than in healthy individuals, However, there was no significant difference in the % predicted values of lung function test parameters among individuals with and without MetS. There was no statistically significant relationship between spirometry parameters and MetS in Park and Larson study. . Several studies have reported that people with MetS are more likely to have milder COPD and better FEV1 [14, 31, 32].
The results of multiple logistic regression analysis showed that older age, female gender, low level of education, urbanization, overweight and obesity are the most important predictors of MetS that were consistent with the results of other studies in Iran and other countries [33–37].
One of the strengths of our study is the use of a population sample with a sufficient sample size that can be a good representative of our study population and this increases the generalizability of the findings of this study. One of the main limitations of the cross-sectional study is that it does not allow causal conclusions, and prospective studies are needed to better understand the role of metabolic syndrome and its components in the development of COPD.