Effect of abnormal body weight on mortality and functional recovery in adults after stroke: An umbrella review.

Background: Several published systematic reviews have drawn conflicting conclusions on the effect of abnormal body weight (i.e. being underweight, overweight or obese) on outcomes following stroke. The 'obesity paradox' seen in several diseases (wherein obesity, often associated with mortality and morbidity, appears to be protective and improve outcomes) may be evident after stroke, but inconsistent results of existing reviews, and the issue of being underweight, are worth investigating further.

Aims: To better understand the impact of body weight on prognosis after stroke, we aimed to answer the following research question: What is the effect of abnormal body weight (underweight, overweight, or obesity) on mortality and functional recovery in adults after stroke?

Summary of review: We conducted an umbrella review to synthesize existing evidence on the effects of abnormal body weight on stroke outcomes. We searched Cumulated Index to Nursing and Allied Health Literature (CINAHL) Complete, COCHRANE Database of Systematic Reviews, PubMed, Medline, PEDro, and EMBASE Classic + EMBASE, from inception until 28 February 2023. Seven systematic reviews (1,136,929 participants) from 184 primary studies (counting duplicates) were included. While the risk of mortality increases with being underweight (body mass index (BMI) < 18.5 kg/m²), excess body weight (being overweight (BMI = 25-29.9 kg/m²) or obese (BMI > 30 kg/m²)) is associated with reduced mortality. The impact of abnormal body weight on functional recovery is less clear; data from studies of being underweight are associated with poor functional outcomes while those from studies of excess body weight are inconclusive.

Conclusion: Abnormal body weight effects post-stroke outcomes and should be considered in clinical decision-making, prognostic research, and clinical trials of rehabilitation interventions. The "obesity paradox" is evident after stroke, and excess body weight is associated with reduced mortality compared to normal body weight. It is recommended that body weight is routinely recorded for stroke patients, and further research, including well-designed cohort studies with reliable weight data, is needed to further investigate the impact of body weight and distribution on post-stroke outcomes.