Background SLE originates from the complex interplay between genetic, epigenetic and environmental factors but the effects of the latter remain elusive. Very few studies have examined the impact of the place of residence (urban/rural) on SLE clinical profile and outcomes.
Objectives To evaluate the effect of rural versus urban place of residency with regards to: i) SLE occurrence; ii) delay in diagnosis; iii) clinical manifestations, severity and non-reversible organ damage; iv) comorbidities and hospitalizations.
Methods We employed data from the Lupus Epidemiology & Surveillance project in Crete (750 adult SLE patients with ≥4 ACR-1997 classification criteria). Crete is a Mediterranean island with genetically stable and homogenous population in ethnicity and sociodemographic characteristics, with no significant inequalities regarding access to healthcare facilities; 61% of the inhabitants live in rural (<10,000 people) and 47% in urban areas (>10,000 people). Demographics and residency history were retrieved from face interviews. In 200 patients with exclusively urban or rural residence, a subanalysis was performed in relation to disease risk, diagnosis age, disease severity, renal and neuropsychiatric involvement, and organ damage (SLICC damage Index [SDI]).
Results SLE prevalence (December 2013) varied across the four geographical prefectures of Crete (Figure 1) and was significantly higher in urban (165/105) than rural (123/105) areas (p<0.001). The relative risk of SLE in urban versus rural regions was 2.0 (95% Confidence Interval 1.5–2.9). Notably, patients in urban regions had lower age of diagnosis (38.0±13.4 vs. 44.5±14.8 years, p=0.005) and female-to-male ratio (6.5:1 vs. 11:1) than those in rural regions. Delay >2 years between symptoms onset and SLE diagnosis occurred in 42% of patients from rural areas as compared to 32% of those from urban areas (p=0.01). Acute cutaneous lupus was more prevalent in the rural environment (83.9% vs. 72.6%, p=0.05) whereas the opposite trend was noted for discoid rash (2.3% vs. 16.8%, p=0.001). Nephritis occurred less frequently (10.3% vs. 12.4%) and neuropsychiatric disease was more prevalent (14.9% vs. 10.6%) in rural than urban patients albeit non-significantly. Prevalence of mild, moderate, and severe disease was 42%, 40%, and 18% in patients from rural areas, the respective figures being 55%, 28% and 18% in those from urban areas (p=0.12). Hospitalization due to active lupus did not differ between the two groups. At last follow-up, 45.3% of the patients living in urban and 51.9% of patients in rural areas had no organ damage (p=0.89). Concurrent allergic diseases were more frequent in urban patients (30.9% vs. 14.3%, p=0.045), particularly allergic rhinitis (8.8% vs. 2.3%, p=0.05).
Conclusions SLE may be more prevalent in urban than rural regions and urbanization is associated with increased risk of SLE and earlier age of disease onset.
Our results suggest an important effect of the environment on SLE occurrence and characteristics, which warrants further investigation.
Disclosure of Interest None declared