Serum magnesium levels in stable and acute exacerbation of bronchial asthma: A prospective observational study

Abstract

Background: Magnesium is an essential cation involved in bronchial smooth muscle relaxation and modulation of airway inflammation. However, prospective spirometry-linked data on serum magnesium levels across the spectrum of asthma in North India remain limited. This study aimed to compare serum magnesium levels in stable bronchial asthma and acute exacerbation and evaluate their association with pulmonary function and disease characteristics. Materials and Methods: This prospective observational study was conducted at Tertiary care hospital, Srinagar, for 1 year. One hundred physician-confirmed asthma patients were enrolled, including 68 with stable asthma and 32 with acute exacerbation. Serum magnesium was estimated using the colorimetric xylidyl blue method, and spirometry was performed using a calibrated spirometer. Statistical analyses included independent t-test, chi-square test, ANOVA, Pearson correlation, and multivariate logistic regression. Within-group Pearson correlations were performed separately to prevent between-group variance inflation. Bonferroni correction was applied for multiple comparisons, and ROC curve analysis was used to assess diagnostic utility of serum magnesium. A p-value <0.05 was considered significant. Results: Mean serum magnesium was significantly lower in the acute exacerbation group compared to the stable asthma group (1.62 ± 0.31 vs 1.98 ± 0.28 mg/dL,p<0.001). Hypomagnesaemia(<1.7mg/dL)wasobservedin68.8%ofexacerbationcasesversus17.6%ofstablecases(p<0.001). Within-groupPearson correlation analyses (performed separately per group to avoid between-group variance inflation) demonstrated significant positive associations between serum magnesium and FEV 1 (r=0.440), FVC (r=0.388), FEV 1 /FVC ratio (r=0.314), and PEFR (r=0.422) within the stable group, and corresponding associations within the exacerbation group; all correlations within the stable group survived Bonferroni correction (adjusted α =0.0125). ROC curve analysis confirmed good diagnostic utility of serum magnesium in discriminating stable asthma from acute exacerbation (AUC=0.806; 95% CI: 0.721–0.890; p<0.001; optimal cut-off=1.78 mg/dL, sensitivity 70.2%, specificity 75.7%). Lower magnesium levels were also associated with longer disease duration and frequent exacerbations. Conclusion: Lower serum magnesium levels were significantly associated with acute asthma exacerbation, reduced pulmonary function, longer disease duration, and frequent exacerbations. While the smaller exacerbation subgroup warrants cautious interpretation, the findings support further randomized controlled trials evaluating magnesium supplementation in hypomagnesaemic asthma patients to determine its effect on spirometric outcomes and exacerbation frequency.