Impact of underweight on 3-year all-cause mortality in patients with acute severe hypertension: a retrospective cohort study

Body mass index (BMI) is used to measure body fat. We investigated the association between BMI and long-term clinical outcomes in patients with acute severe hypertension who visited the emergency department (ED). Cross-sectional study data were obtained from a single regional emergency medical center, including patients with elevated initial systolic blood pressure ≥ 180 mmHg or diastolic blood pressure ≥ 100 mmHg. The patients were classified into five groups according to BMI level (underweight, normal, overweight, obese class I, II and III). Among 4867 patients who presented with acute severe hypertension at the ED, 935 (19.21%) died within 3-years. In particular, 140 (44.59%) patients in the underweight group died from any cause, which was the highest among the five groups, and there was a reverse J-shaped association between BMI and 3-year all-cause mortality. Underweight patients had a significantly increased risk of all-cause mortality by 1.55-fold during the 3-year follow-up. Rather, obesity was associated with a reduction in the 3-year all-cause mortality. Comorbidities, including chronic kidney disease and acute hypertension-mediated organ damage, were independent predictors of all-cause mortality in patients who were not underweight. Underweight contributes to worsening long-term clinical outcomes in patients with acute severe hypertension. Clinicians should consider BMI as one of the physical examination parameters in patients with acute severe hypertension, and management including lifestyle modifications such as diet control and exercise should be undertaken considering BMI and comorbidities.