The association between abnormal serum magnesium levels and prognosis of elderly patients with community-acquired pneumonia.

To investigate the association between abnormal serum magnesium levels and the prognosis of elderly patients with community-acquired pneumonia (CAP). Methods: A retrospective study was conducted on 1381 elderly patients with CAP in the First Hospital of Qinhuangdao between January 2015 and December 2018. Serum magnesium concentrations in the range of 0.75-1.25 mmol/L were defined as normal. Patients were assigned into normal, hypomagnesemia, and hypermagnesemia groups. The primary outcome was in-hospital mortality, indicating whether a patient died at the time of discharge from the hospital. The percentages of respiratory failure and mechanical ventilation were 18.6% and 10.6 % in the normal group, 29% and 16.5 % in the hypomagnesemia, and 42.9% and 35.7% in the hypermagnesemia groups. The occurrence of shock was 8.5% and 4.5% in the hypomagnesemia group and the normal group. The percentages of the length of stay at ICU were 14.9%, 18.8%, and 57.1% in the hypomagnesemia, normal, and hypermagnesemia groups. The in-hospital mortality rate was 5.3%, 9.1%, and 35.7% in the normal, hypomagnesemia, and hypermagnesemia groups, respectively. The results of univariate analysis showed that the in-hospital mortality in the hypomagnesemia group was 1.790 (95% confidence interval (CI): 1.009∼3.176, P=0.046) times higher than that in the normal group; in the hypermagnesemia group, it was 9.947 (95% CI: 3.238-30.556, P<0.001) times higher than that in the normal group. The results of multivariate logistic regression analysis showed that after adjusting for gender, age, diabetes, heart failure, cerebrovascular disease, cancer, estimated glomerular filtration rate (eGFR), glucose, and CURB-65 score, in the hypomagnesemia group, the in-hospital mortality was 1.746 (95% confidence interval (CI): 0.956∼3.186, P=0.070) times higher than that in the normal group, and 5.689 (95% CI: 1.583- 20.446, P=0.008) times higher in the hypermagnesemia group than that in the normal group. Abnormal serum magnesium levels are strongly associated with in-hospital mortality in elderly patients with CAP. The measurement of serum magnesium levels in elderly patients with CAP at admission may assist clinicians to determine the prognosis of such patients.