April 22, 2019
2 min read

‘Obesity paradox’ present in heart attack-related mortality

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Adults admitted to the hospital for acute myocardial infarction who are categorized as having underweight may be at a higher mortality risk than those with other weight statuses, including obesity, according to findings from researchers in China.

“Although obesity is a well-established risk factor for cardiovascular disease, many studies demonstrated that overweight or obese patients have lower risk of in-hospital or longer-term adverse events compared with patients with normal weight in various clinical settings,” Yuejin Yang, MD, PhD, of the department of cardiology at Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, National Center for Cardiovascular Diseases, State Key Laboratory of Cardiovascular Disease in China, and colleagues wrote. “Some studies supported the phenomenon of ‘obesity paradox’ by demonstrating that overweight and obesity were associated with decreased mortality risk.”

Yang and colleagues used data from the China Acute Myocardial Infarction registry, which collected information from patients admitted to 108 hospitals with acute MI from 2013 to 2016. Yang and colleagues analyzed data from 35,964 adults aged 18 to 100 years who had BMI calculations available.

Participants with a BMI of less than 18.5 kg/m2 were considered to have underweight (n = 919; mean age, 70.63 years; 41.9% women). Participants with a BMI between 18.5 kg/m2 and 24.9 kg/m2 were considered to have normal weight (n = 21,984; mean age, 63.99 years; 26.4% women). Participants with a BMI between 25 kg/m2 and 30 kg/m2 were considered to have overweight (n = 11,675; mean age, 60.15 years; 22.8% women). Participants with a BMI of at least 30 kg/m2 were considered to have obesity (n = 1,386; mean age, 56.63 years; 26.3% women).

The researchers found that participants with underweight had a higher mortality rate (11.3%) compared with those with normal weight (6%), overweight (4.2%) and obesity (3%; P < .001 for all). In addition, underweight status was associated with an approximately twofold unadjusted increase in mortality risk compared with normal weight (OR = 2.01; 95% CI, 1.62-2.48). Based on the same unadjusted data, participants with overweight (OR = 0.69; 95% CI, 0.62-0.76) and those with obesity (OR = 0.49; 95% CI, 0.36-0.67) had lower risks for in-hospital mortality compared with participants with normal weight. According to the researchers, the relationships held for participants with underweight (OR = 1.29; 95% CI, 1.02-1.64), overweight (OR = 0.83; 95% CI, 0.75-0.93) and obesity (OR = 0.72; 95% CI, 0.56-0.92) compared with normal weight after adjusting for factors such as age, hypertension and previous MI.


“We still recommend patients to prevent obesity post [acute] MI. This is because most studies demonstrated that obese patients were at higher risk of comorbidities, including diabetes, hyperlipidemia and hypertension,” the researchers wrote. “The second implication of our results is that clinicians should pay more attention to underweight patients. ... When treating underweight patients with [acute] MI, clinicians should not only start a regular secondary prevention treatment, but also manage other prognostic factors, including malnutrition status and potential [comorbidities].” – by Phil Neuffer

Disclosures: The authors report no relevant financial disclosures.