Hypomagnesaemia in chronic, stable asthmatics: prevalence, correlation with severity and hospitalization

Magnesium (Mg) deficiency is associated with airway hyperreactivity, wheeze and impairment of lung function. The prevalence of hypomagnesaemia, and its effect on asthma is unclear. Therefore, this prospective study was undertaken to evaluate the prevalence of low serum Mg level, to correlate whether hypomagnesaemia (serum Mg level <0.74 mmol x L(-1)) is associated with severity of asthma and increased frequency of hospitalizations in chronic, stable asthmatics. Ninety-three chronic stable asthmatics, who were on regular follow-up in an asthma clinic, were studied. On attendance to the asthma clinic, each subject was interviewed and clinically evaluated. The serum Mg level (normal 0.74-1.2 mmol x L(-1)), as well as the severity of asthma was measured. The medications used were recorded. The total number of hospitalizations due to asthma exacerbation was scored for the last three months that preceded the date of measuring the serum Mg level. Twenty-five patients (27%) had a low Mg level with a mean+/-SD of 0.69+/-0.04 mmol x L(-1), while 68/93 (73%) had a normal Mg level (0.82+/-0.08 mmol x L(-1)). The number of hospitalizations in asthmatics with low Mg levels was 10/25 (40%), compared to 8/68 (12%) (p<0.01) in asthmatics with normal Mg levels. Multiple logistic regression analysis showed that severe asthma was the only factor associated significantly with hypomagnesaemia (p=0.04). No effect was observed for inhaled beta-agonist, inhaled steroid or theophylline therapy on serum Mg level. To conclude, hypomagnesaemia is common in chronic asthmatics. Chronic asthmatics with low Mg tend to have more hospitalizations than chronic asthmatics with normal Mg. Hypomagnesaemia was also associated with more severe asthma.