Epidemiology of primary Sjögren's syndrome in north-west Greece, 1982-2003

To investigate the incidence and prevalence, as well as the mortality and survival rates, of primary Sjögren's syndrome (pSS) in a defined area of north-west Greece with a population of about 500 000 inhabitants.

Cases were recorded from the following sources: (i) in- and out-patients referred to the rheumatology clinics of the Ioannina University Hospital and the Ioannina General Hospital; and (ii) patients referred to private rheumatologists practising in the study area. All patients diagnosed between 1 January 1982 and 31 December 2003 who were resident in the study area were included as incident cases. Diagnosis was based on the American-European consensus criteria for SS. Incidence and prevalence rates were calculated as numbers of cases per 10(5) inhabitants. Population data were based on the National Censuses of 1981, 1991 and 2001.

A total of 422 incident cases were identified for the study period 1982-2003. Age-adjusted mean annual incidence rate for this period was 5.3 (95% confidence interval [CI] 4.5-6.1) cases per 10(5) adult inhabitants. The female/male ratio of incident cases was about 20/1. The age-adjusted prevalence rate for the adult population was 92.8 (95% CI 83.7-101.9) cases per 10(5) inhabitants on 31 December 2003. The 5-yr survival rate in the incidence cohort was 96.6% and the 10-yr survival rate 92.8%. The standardized mortality ratio in comparison with the general population of the study area was 1.02 (95% CI 0.4-2.0). The main causes of death were cardiovascular diseases and cancer. The occurrence of the disease shows a slightly decreasing, but not statistically significant, trend with time.

The estimated incidence and prevalence of pSS in this study were slightly higher in comparison with data from other studies based on physician-diagnosed cases. The prevalence was significantly lower when compared with the findings of studies based on the examination of a sample of the general population. Mortality rates did not differ significantly between pSS patients and the general population.