Impact of body mass index on clinical outcomes in pediatric patients with mycoplasma pneumoniae pneumonia: a retrospective cohort study.

Background: The incidence of mycoplasma pneumoniae pneumonia (MPP) has increased globally, particularly among children and adolescents. Obesity, a major public health challenge, may affect the severity and clinical manifestations of respiratory infections. However, the prognostic role of body mass index (BMI) in MPP remains unclear. This study aimed to investigate the relationship between BMI and clinical outcomes in pediatric patients with MPP. Methods: This retrospective study included 530 children (aged 2-14 years) hospitalized with MPP at Shaoxing People's Hospital between May 2024 and August 2024. Participants were categorized into obesity, overweight, and normal weight groups based on BMI standards. Inclusion criteria required a confirmed diagnosis of MPP according to the National Health Commission's guidelines. Demographic characteristics, clinical factors such as fever, dyspnea, rash, pleural effusion, plastic bronchitis, and laboratory findings were compared among BMI groups. Prognostic outcomes (including duration of fever, length of hospital stay, incidence of plastic bronchitis, and pleural effusion) were assessed, with severe MPP (SMPP) serving as the primary endpoint. The Pearson correlation coefficient was used to evaluate associations between BMI and clinical variables, while binary logistic regression was performed to analyze the relationship between BMI and SMPP. Results: Forty-two patients had obesity (7.9%), 45 were overweight (8.5%), and 443 (83.6%) had normal BMI. There were no significant differences in age, gender, and height distribution among three groups. A longer duration of fever (P=0.01), along with a greater incidence of dyspnea (P=0.006), plastic bronchitis (P=0.007), and SMPP (P=0.008) was observed in the obesity and overweight groups compared to the normal weight group. Laboratory results showed elevated white blood cell count (WBC, P<0.001), neutrophil count (N, P<0.001), and C-reactive protein (CRP, P=0.001) levels in the overweight and obesity groups compared to the normal weight group. Additionally, significant increases in red blood cell count (RBC, P=0.03), and alanine aminotransferase (ALT, P=0.006) levels were observed in the obesity group compared to the normal weight group. Correlation analysis revealed that higher BMI was positively associated with the duration of fever (P=0.03) and levels of WBC (P<0.001), N (P<0.001), CRP (P<0.001), RBC (P=0.009), and ALT (P<0.001). Logistic regression analysis demonstrated that higher BMI was associated with an increased risk of SMPP [odds ratio (OR) =1.143, 95% confidence interval (CI): 1.045-1.250]. This association remained significant after adjusting for age and gender (OR =1.120, 95% CI: 1.020-1.231). Conclusions: This study underscored the critical role of overweight and obesity in exacerbating the severity of MPP in pediatric patients. Higher BMI was associated with an increased risk of more severe clinical manifestations, such as prolonged fever, dyspnea and complications like plastic bronchitis. Clinicians should prioritize BMI assessment when managing MPP to improve outcomes and implement targeted preventive strategies for obese patients.