Rheumatology 2003; 42: 1122-1123
© 2003 British Society for Rheumatology
Letters to the Editor |
Survival and mortality rates of systemic lupus erythematosus patients in northwest Greece. Study of a 21-year incidence cohort
Department of Hygiene and Epidemiology and
1 Division of Rheumatology, Department of Internal Medicine, Medical School, University of Ioannina, Ioannina, Greece
SIR, Studies carried out in different countries suggest significant variation in the survival rate of patients with systemic lupus erythematosus (SLE) [1, 2]. These findings could be related to different severity of the disease among populations, although access to efficient treatment and methodological differences among studies could explain these variations in part. Genetic, ethnic and environmental factors seem to be involved in the expression and severity of SLE [3–7].
The epidemiological and clinical profile of SLE in northwest Greece indicates a relatively low occurrence and mortality of the disease, with a low mean age at diagnosis and a high proportion of mild cases [8, 9]. In this study, survival of SLE patients and its association with sociodemographic parameters were examined in a 21-yr incidence cohort in this defined area.
All patients resident in a defined area of northwest Greece and diagnosed between 1 January 1981 and 31 December 2001 were included in the study. Patients were referred in the framework of a systematic recording system for autoimmune rheumatic diseases in northwest Greece. A total of 185 SLE patients fulfilled these criteria and entered the study. This number represented a mean annual incidence rate of about 2 cases per 105 inhabitants [9]. The study area, the sources and methods of patients recording, the definition of an incidence case and the clinical characteristics of the cohort have been described in detail previously [9]. Of our patients, 15.2% presented renal disorders at first diagnosis. Survival was determined from the date of first diagnosis (entry point) to 39 June 2002. A total of 21 patients died during the follow-up period and six were lost from follow-up. Survival rates were estimated using the Kaplan–Meier method. Differences in survival between patient groups were determined using the log-rank test. Cox's proportional hazards model was used to examine the independent association of several parameters with the risk of death.
The 5-yr survival rate for the total cohort was 96.2% [95% confidence interval (CI) 93.4–99.0] and the total 10-yr survival rate was 87.4% (95% CI 81.8–93.0).
Survival curves differ significantly between sexes (P < 0.05), with a better prognosis for women. Patients with early onset of the disease (<45 yr) presented a poorer survival than patients with a later onset (
45 yr), but survival curves did not differ at a statistically significant level. Survival rates tend to improve slightly during the last decade.
Table 1
shows the risk of death (hazard ratios) in relation to sex, age at diagnosis, time of diagnosis and residence. Sex showed a significant association with the risk of death independently of the other parameters included in the model. Time of diagnosis and age of diagnosis also tended to correlate with risk of death, but the differences observed were not statistically significant. The risk of death did not differ significantly between residents of urban and rural areas.
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The standardized mortality ratio (SMR) for the total cohort was 1.5 (95% CI 1.3–1.8) in comparison with the general population of the area studied (standardized for age and sex). It was slightly higher for the period 1981–1990 than for the period 1991–2001 [1.6 (95% CI 1.4–1.9) vs 1.5 (95% CI 1.3–1.8)]. The most common causes of death observed among our SLE patients were cardiovascular disease (five cases), neoplasia (four), end-stage renal disease (two) and infection (two).
According to the results of the present study, SLE patients in northwest Greece present relatively high survival rates compared with patient series from other countries. Results of other survival studies indicate 5-yr survival rates between 56 and 98%, and 10-yr survival rates between 50 and 93% [4–8]. However, the total survival of our inception cohort was significantly lower than that in the general population, as indicated by the SMR.
Among several sociodemographic factors studied in our cohort, only sex showed a significant independent association with survival. This is in agreement with findings of other studies suggesting a poorer life expectancy for men than for women SLE patients [7]. Patients with a low age of disease onset are reported to have poorer survival, although data in this field are controversial, suggesting a bimodal pattern and with poorer prognosis in both youngest and oldest patients [7, 10]. In the present study the younger group of patients tended to have a higher risk of death, but not at a statistically significant level.
In summary, the total survival rates were higher than survival rates reported in other studies, mainly in studies based on hospital series, and showed a slight improvement during the last decade. This could be related to a better diagnosis and recognition of milder cases of the disease during the later years [9]. Gender appears to be an independent prognostic factor, with a better prognosis for females. Young age at disease onset is related to an increased risk of death.
Notes
Correspondence to: A. A. Drosos, Department of Internal Medicine, Medical School, University of Ioannina, 45110 Ioannina, Greece. E-mail: adrosos{at}cc.uoi.gr 
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