Does BMI affect functional outcomes in stroke patients on rehab?

A study in Singapore provides further evidence regarding the benefits of poststroke rehabilitation in improving function, reducing disability, and discharging patients. In addition, the results show that body mass index (BMI) in any category does not predict the ability to attain functional independence following inpatient rehabilitation.

“Findings from this study unequivocally support the benefits of acute inpatient stroke rehabilitation,” said lead author Sze Chin Jong, Division of Rehabilitation Medicine, University Medicine Cluster, National University Hospital, Singapore. “BMI — whether underweight, normal, or overweight—did not correlate with discharge functional independence measure [FIM].”

Jong and colleagues conducted this prospective, observational cohort study and enrolled 247 stroke patients (mean age, 59.48 years) admitted to a single inpatient rehabilitation unit. Using the World Health Organization (WHO) Asian standards, the research team classified BMI as underweight (<18.5 kg/m²), normal (18.5–22.9 kg/m²), and overweight (≥23 kg/m²).

Discharge FIM was the primary outcome, while secondary ones included FIM gain, FIM efficiency, and FIM effectiveness. [Singapore Med J 2024;65:223-228]

Of the admitted patients, 159 (64.4 percent) were male and 130 (52.6 percent) had ischaemic stroke. BMI assessment upon admission showed 27 (10.9 percent) patients were underweight, 82 (33.2 percent) normal weight, and 138 (55.9 percent) overweight. Upon discharge, 29 (11.7 percent) patients were underweight, 94 (38.1 percent) normal, and 124 (50.2 percent) overweight.

Small but significant reductions in BMI were observed from admission to discharge (median, 23.58 vs 23.12 kg/m²; p<0.001). There were also clinically significant FIM gains (mean ΔFIM, 26.71; 95 percent confidence interval, 24.73‒28.69; p<0.001) seen after a median length of stay of 36 days.

Notably, BMI showed no significant association with discharge FIM (p=0.600), FIM gain (p=0.254), FIM efficiency (p=0.412), or FIM effectiveness (p=0.796).

“Overall, our findings showed that BMI in any category was neither associated with nor predictive of rehabilitation functional outcome as measured by the discharge FIM score or the ability to make significant functional gains after inpatient rehabilitation,” Jong said. “All patients in the three BMI categories achieved significant FIM gains [total, motor, and cognitive].”

Obesity paradox

Moreover, thinner patients had a tendency to achieve slightly higher FIM gains than those with obesity. This finding contrasted the “obesity paradox” seen in larger population-based studies. [Arch Phys Med Rehabil 2014;95:1055-1059; J Stroke Cerebrovasc Dis 2014;23:e201-206; BMJ Open 2015;5:e008712]

“This might be because the majority of underweight patients in our study were nutritionally replete, as only 18.5 percent had low albumin levels,” Jong said. “We speculate that higher lean muscle mass in the underweight BMI class could augur higher functional reserves and thus better FIM outcomes, and that younger stroke cohorts are less likely to have age-dependent sarcopenia.”

Data from the WHO showed that Singapore has the second highest prevalence of overweight people in Southeast Asia. More than half of the patients in the current study were overweight upon admission. [http://apps.who.int/iris/bitstream/handle/10665/148114/9789241564854_eng.pdf?sequence=1]

Previous studies have reported that overweight could increase the risk of stroke, gait dysfunction, and poststroke mortality and morbidity, which could then impact discharge FIM and FIM gain. [PM R 2014;6:908-913; Am J Phys Med Rehabil 2012;91:951-956; Arch Phys Med Rehabil 2014;95:472-479]

“Long-term follow-up of this cohort is a logical next step to study the impact of BMI,” Jong said.