BACKGROUND:Although atrial fibrillation (AF) is an important cause of cardiovascular morbidity and mortality there is a paucity of data describing hospitalisation rates and case-fatality associated with this common arrhythmia. This study examines recent trends in first-ever hospitalisations for AF in Scotland. METHODS:Using the linked Scottish Morbidity Record Scheme, we identified all 22968 patients admitted to Scottish hospitals for the first time with a principal diagnosis of AF between 1986 and 1995. For each calendar year we calculated short (30-day) and medium (31 day to 2 years) case-fatality rates. Adjusting for each patient's age, sex, deprivation status, concurrent diagnoses and prior hospitalisation status, we examined whether case-fatality rates had significantly improved during this 10-year period. RESULTS:Between 1986 and 1995 the number of men hospitalised for the first time with AF increased by 926 (125%) to 1730 per annum and the number of women and by 875 (105%) to 1712 (both P<0.001). Hospitalisation rates increased from 0.31 to 0.70/1000 men and from 0.32 to 0.65/1000 women (both P<0.001). By the end of this period the proportion of men had increased from 48 to 50%. In both sexes, the median age of patients rose--in men from 66 to 68 years and in women from 74 to 75 years (both P<0.01). Despite the increasing age of patients and greater comorbidity, short-term (30-day) case-fatality declined from 4.0 to 3.1% in men (P<0.001) and 4.1 to 3.8% (P<0.01) in women. Similarly, medium-term (31-day to 2-year) case-fatality fell from 25 to 22% in men and 27 to 25% (both P<0.001) in women. Adjusting for the age, sex, extent of deprivation, secondary diagnoses and prior hospitalisation of hospitalised patients, we found that the risk of short-term case-fatality in the 1995 male and female cohort significantly declined by 21% (P<0.05) and 24% (P<0.05), respectively, in comparison to the 1986 cohort. The adjusted risk of case-fatality in the medium term also declined significantly in men by 30% (P<0.05) over this period and by 20% (P<0.05) in women relative to 1986. CONCLUSION:The number of first-ever hospitalisations for AF has increased twofold during the 10-year period 1986-1995. Although the age of patients has progressively increased during this period, short and medium case-fatality rates have declined, especially in men. This may partly reflect better treatment of AF. However, changing admission thresholds and other factors could also have led to an apparent improvement in prognosis. Nevertheless, medium-term case fatality remains substantial after a first ever admission to hospital with AF.