Risk factors for developing systemic lupus erythematosus: a case-control study in southern Sweden.
OBJECTIVE
To explore the risk factors that have been suggested to be associated with the development of SLE.


METHODS
A case-control study was performed and a questionnaire was developed to obtain the data. Consecutive female incident cases diagnosed between 1981 and 1999 in a defined geographical area in southern Sweden were included. Controls, matched for calendar year of birth, were selected randomly from the same area. In total, 85 cases and 205 controls agreed to participate. The questionnaire included questions about formal education, body weight and height, medical history, family history of autoimmune diseases, exposure to ultraviolet radiation, animals, hair-colouring dyes, alfalfa (lucerne) sprouts, smoking and alcohol habits, history of physical traumata, blood transfusion, silicone breast implants, exogenous oestrogens, other medication, and significant negative life events.


RESULTS
Using a multivariate model, a history of hypertension [odds ratio (OR)=3.7, 95% confidence interval (CI) 1.4-9.8], drug allergy (OR=3.6, 95% CI 1.4-9.5), a type I/II sun-reactive skin type (OR=2.3, 95% CI 1.1-4.8) and a family history of SLE (OR=6.8, 95% CI 1.4-32) were all significantly associated with an increased risk of developing SLE, whereas consumption of alcohol was inversely associated with the risk of SLE (use of alcohol very seldom, OR=1.0; 1-150 g/month, OR=0.4, 95% CI 0.2-1.0; >150 g/month, OR=0.2, 95% CI 0.1-0.5). A suggested association with increased SLE risk was seen for smoking (OR=1.8, 95% CI 0.9-3.6) and blood transfusions (OR=2.3, 95% CI 0.9-5.8). Neither exposure to exogenous oestrogen nor exposure to hair-colouring dyes was associated with SLE.


CONCLUSIONS
Risk factors of both exogenous and endogenous origin were identified in this population-based series of SLE patients.
Bengtsson
A A
AA
Department of Rheumatology, University Hospital of Lund, S-221 85 Lund, Sweden.
Rylander
L
L
Hagmar
L
L
Nived
O
O
Sturfelt
G
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000453:epidemiology*; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011897:Random Allocation; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology