New research shows that that younger, overweight stroke patients have a lower 10-year mortality compared with normal-weight survivors and that compared with nonsmokers, those who smoke have a lower in-hospital mortality rate after an acute ischemic stroke, whether or not they received intravenous tissue plasminogen activator (IV tPA).

Research exploring the obesity paradox and the smoking paradox was presented in separate reports here at the American Academy of Neurology (AAN) 67th Annual Meeting.

In one presentation, Hugo Javier Aparicio, MD, vascular neurology fellow, Department of Neurology, Boston University School of Medicine, and an investigator in the Framingham Heart Study, said the obesity paradox has been observed in myocardial infarction, congestive heart failure and end stage kidney disease, as well as in stroke.

“Obese and overweight patients have been shown to have lower mortality and also suffer lower stroke recurrence,” he said.

The reasons for this paradox are unclear, but some experts have questioned whether there’s some physiologic advantage to being obese, of having excess fat storage or a “metabolic reserve” at the time of an illness, said Dr Aparicio.

Selection Bias

Other experts have focused on confounding or selection bias possibly being at play, he said. For example, obese patients may present earlier, or get treated at a younger age.

For this new analysis, Dr Aparicio and his colleagues used a sample from the Framingham Study, both the original and the offspring cohorts. They used the following weight categories: underweight: body mass index (BMI) less than 18.5; normal weight, BMI 18.5 to less than 25; overweight, BMI 25 to less than 30 and; obese 30 or greater.

They also subcategorized the groups into low overweight (BMI, 25 to 27.5), high overweight (BMI, 27.5 to 30), mildly obese (BMI, 30 to 32.5), and very obese (BMI, 32.5 or greater).

The analysis included 677 participants with stroke and 2031 controls without stroke matched for age, sex, and BMI. Patients with stroke were more likely to smoke, have other cardiovascular risk factors, and be receiving blood pressure and diabetes treatment before inclusion in the trial.

In both the stroke and controls group, 30% were normal weight, 44% were overweight, and 26% were obese.

No patients with stroke were underweight at the examination before their stroke.

Using a multivariable Cox proportional hazard model with mortality as outcome and adjusting for age, sex, time between examinations, event date, education, marital status, and smoking, researchers found no difference between the weight groups in the 1-year mortality rate among stroke patients.

In controls, 10-year mortality did not significantly differ in the various weight groups.

The effect seen in the overweight group was maintained in both the low and high overweight groups. There was also a significant difference in the mildly obese (HR, 0.60; 95% CI, 0.42 - 0.86; P = .005) but not in the very obese.