Weight loss after a stroke and inflammation

Abstract

Objective Weight loss in the elderly is a common and problematic phenomenon, and is linked with increased risk of infections, ulcers and mortality. Inflammation appears to have a role in weight loss in conditions such as cancer and Alzheimer’s disease, through mechanisms such as cytokine-inhibition of gastric function and hormones. The mechanism for weight loss after a stroke is currently unclear, but an inflammatory component has been postulated. We therefore sought to explore if weight loss after a stroke is associated with inflammation and stroke severity. Methods Stroke patients (n=37, mean age 70±8 years) were measured at baseline (within 72 hours of stroke), 6 months and 2 years. Right and left mid-arm muscle circumferences (MAMC) and triplicate biceps and triceps skin folds were measured. MAMC is an anthropometric proxy for BMI in those who could not have height or weight measured. Means of the triplicates were used to calculate proportion body fat. Changes were calculated as baseline minus follow-up data. Inflammatory cytokines IL-6 and TNFα were measured by ELISA in plasma taken at baseline, 6 months and 2 years. Results The stroke group had a decrease in MAMC (32.2±3.7 v. 30.8±3.9cm, p=0.009) but no change in body fat. Most of the loss appeared in the first 6 months. The change in MAMC was associated with lower systolic blood pressure on admission (R=-0.417, p=0.022), a more severe stroke (Barthel score <72 hours after stroke; R=-0.450, p=0.006; and at 6 months, R=-0.350, p=0.049), increased IL-6 at 6 months (R=0.458, p=0.007) and increased TNFα (R=0.425, p=0.012). There was no association with stroke subtype, post-stroke infection, or nasogastric tube feeding. Multivariate analysis suggests that a model containing TNFα alone is associated with 55% of the variation in change in MAMC seen in the stroke group. Conclusion After stroke, there was a reduction in MAMC over 2 years, and particularly in the first 6 months. Stroke patients with the largest changes in MAMC tended to be those who presented with the most severe strokes and the highest level of pro-inflammatory cytokines, particularly TNFα levels. These data suggest that weight loss after a stroke may have an inflammatory component.