Aims: We aimed to evaluate the association between metabolic syndrome (MetS) and long-term all-cause mortality.
Methods and results: The LIPIDOGRAM studies were carried out in the primary care in Poland in 2004, 2006, and 2015. MetS was diagnosed based on the National Cholesterol Education Program, Adult Treatment Panel III (NCEP/ATP III), and Joint Interim Statement (JIS) criteria. The cohort was divided into four groups: non-obese patients without MetS, obese patients without MetS, non-obese patients with MetS, and obese patients with MetS. Differences in all-cause mortality were analysed using Kaplan-Meier and Cox regression analyses. A total of 45 615 participants were enrolled (mean age 56.3, standard deviation: 11.8 years; 61.7% female). MetS was diagnosed in 14 202 (31%) by NCEP/ATP III criteria and 17 216 (37.7%) by JIS criteria. Follow-up was available for 44 620 (97.8%, median duration 15.3 years) patients. MetS was associated with increased mortality risk among the obese {hazard ratio, HR: 1.88 [95% confidence interval (CI) 1.79-1.99] and HR: 1.93 [95% CI 1.82-2.04], according to NCEP/ATP III and JIS criteria, respectively} and non-obese individuals [HR: 2.11 (95% CI 1.85-2.40) and 1.7 (95% CI 1.56-1.85) according to NCEP/ATP III and JIS criteria, respectively]. Obese patients without MetS had a higher mortality risk than non-obese patients without MetS [HR: 1.16 (95% CI 1.10-1.23) and HR: 1.22 (95% CI 1.15-1.30), respectively in subgroups with NCEP/ATP III and JIS criteria applied].
Conclusions: MetS is associated with increased all-cause mortality risk in non-obese and obese patients. In patients without MetS, obesity remains significantly associated with mortality. The concept of metabolically healthy obesity should be revised.
Keywords: Lean metabolic syndrome; Metabolic syndrome; Obesity.
Metabolic syndrome (MetS) is used to describe a constellation of metabolic disturbances such as elevated blood glucose, increased levels of triglycerides and decreased level of high density lipoprotein cholesterol. They are often accompanied by elevated blood pressure and central obesity, defined as increased waist circumference. Usually, those metabolic disturbances occur in obese individuals, but sometimes, they can also occur in lean subjects. This relatively recent concept is often referred to as lean MetS. A key conclusion from our paper is that MetS, when it occurs in lean patients, is associated with similarly unfavourable long-term prognosis as in obese patients. Additionally, our analysis shows that lean patients with MetS are less often treated with lipid-lowering drugs despite having higher low density lipoprotein cholesterol levels (LDL-C). An additional finding, which is important from a public health perspective, is that obese patients who do not fulfil MetS criteria have higher long-term all-cause mortality than their lean counterparts without MetS. This finding should be an argument to encourage maintenance of normal body weight.
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