BACKGROUND - Low serum magnesium has been linked to increased risk of atrial fibrillation (AF) after cardiac surgery. It is unknown whether hypomagnesemia predisposes to AF in the community.
METHODS AND RESULTS - We studied 3530 participants (mean age, 44 years; 52% women) from the Framingham Offspring Study who attended a routine examination and were free of AF and cardiovascular disease. We used Cox proportional hazard regression analysis to examine the association between serum magnesium at baseline and risk of incident AF. Analyses were adjusted for conventional AF risk factors, use of antihypertensive medications, and serum potassium. During up to 20 years of follow-up, 228 participants developed AF. Mean serum magnesium was 1.88 mg/dL. The age- and sex-adjusted incidence rate of AF was 9.4 per 1000 person-years (95% confidence interval, 6.7-11.9) in the lowest quartile of serum magnesium (≤1.77 mg/dL) compared with 6.3 per 1000 person-years (95% confidence interval, 4.1-8.4) in the highest quartile (≥1.99 mg/dL). In multivariable-adjusted models, individuals in the lowest quartile of serum magnesium were ~50% more likely to develop AF (adjusted hazard ratio, 1.52; 95% confidence interval, 1.00-2.31; P=0.05) compared with those in the upper quartiles. Results were similar after the exclusion of individuals on diuretics.
CONCLUSIONS - Low serum magnesium is moderately associated with the development of AF in individuals without cardiovascular disease. Because hypomagnesemia is common in the general population, a link with AF may have potential clinical implications. Further studies are warranted to confirm our findings and to elucidate the underlying mechanisms.