Metabolic syndrome influences stroke recurrence, all-cause mortality

Metabolic syndrome demonstrated significant correlations with both stroke recurrence and all-cause mortality, according to the results of a meta-analysis of 13 cohort studies with nearly 60,000 participants published in Neurology.

“Several prospective studies and [meta-analyses] have shown that the presence of metabolic syndrome increases the risk of stroke and myocardial infarction, especially in people with prediabetes. Metabolic syndrome has been reported to be an index to predict the occurrence of cardiovascular and cerebrovascular diseases such as diabetes and stroke in non-diabetic people,” the researchers wrote. “However, there are only few related reports about whether metabolic syndrome and its components can predict the risk of recurrent stroke or even death with controversial results.”

Additionally, other studies reported that the presence of metabolic syndrome did not predict stroke recurrence and the conclusion about whether aspects of metabolic syndrome can predict stroke recurrence is also different, according to Fangfang Zhang, MD, of the Second Department of Neurology at Xinxiang Central Hospital in China, and colleagues wrote. These “conflicting studies” led Zhang and colleagues to evaluate the link between metabolic syndrome and its components, which include insulin resistance, obesity, dyslipidemia and hypertension, and subsequent risk for stroke recurrence, as well as other outcomes.

The researchers performed a search for relevant studies with an observational cohort design that were published from database inception through April 23, 2020, using PubMed, Embase and Cochrane Library. They pooled effect estimates with 95% CIs using a random effects model.

Stroke recurrence and all-cause mortality served as the primary and secondary outcomes, respectively. Zhang and colleagues conducted leave-one-out sensitivity analyses and used the nonparametric trim and fill method to examine the stability of the results.

The analysis included 13 cohort studies published between 2008 and 2019 with a total of 59,919 participants aged less than 60 years.

Study results demonstrated that metabolic syndrome was “significantly associated” with stroke recurrence (RR = 1.46; 95% CI, 1.07-1.97). Among the metabolic syndrome components, low levels of high-density lipoprotein cholesterol (RR = 1.32; 95% CI, 1.11-1.57) and the number of metabolic syndrome components ( 2; RR = 1.68; 95% CI, 1.44-1.94) significantly predicted stroke recurrence. However, elevated triglyceride levels, elevated waist circumference, hyperglycemia and hypertension did not account as risk factors for stroke recurrence. Further, metabolic syndrome, but not its components, was significantly associated with all-cause mortality (RR = 1.27; 95% CI, 1.18-1.36), according to Zhang and colleagues.

The leave-one-out sensitivity analyses and nonparametric trim and fill method provided further validation of the stability of these results, the researchers reported.

“The current meta-analysis provides significant future clinical implication for risk of stroke recurrence and mortality in patients with metabolic syndrome or its components, yielding approximate risk estimates,” Zhang and colleagues wrote. “The RRs associated with metabolic syndrome were 1.45 (95% CI, 1.05-2) for subsequent stroke recurrence and 1.25 (95% CI, 1.09-1.43) for all-cause mortality. For patients with metabolic syndrome or its components, early screening and effective interventions are of great importance in the prevention of stroke recurrence and improvement of disease outcomes.”

The researchers noted that the current study is, to their best of their knowledge, “the largest and most comprehensive meta-analysis involving high quality cohort studies of this topic.” The findings provided updated evidence regarding the link between metabolic syndrome or its components and later stroke recurrence or mortality, according to the study results.

However, they also acknowledged several limitations of the research, including “considerable heterogeneity” among the included studies on stroke recurrence, as well as the drawing of conclusions based on observational cohort studies, which prevented the researchers from being able to infer “that there is a direct causal relationship between metabolic syndrome or its components and stroke recurrence or death.” Further research with higher degrees of evidence, such as large prospective cohort studies, is needed to verify these results, according to Zhang and colleagues.

“Despite these mentioned limitations, the current study provides a comprehensive quantitative analysis with a larger sample size conducted for a meaningful and robust statistical analysis,” the researchers wrote.