Office of Border Health

Nogales Arizona Lupus Study

An elevated prevalence of systemic lupus erythematosus (SLE) was reported in Nogales, Arizona and Rio Rico, a nearby community. In March 1997, the Arizona Department of Health Services (ADHS) requested assistancefrom the Centers for Disease Control and Prevention (CDC) to conduct a case-control study to determine whether exposure to chemicals in the environment was associated with SLE among residents of Nogales. We conducted a two-phase study to address this question. The objectives of Phase I were to identify potential SLE cases in Nogales, determine the prevalence of SLE in Nogales and determine if there was a seasonal pattern to the appearance of SLE symptoms. The objectives of Phase II were to identify potential risk factors associated with development of SLE in Nogales and to evaluate the possible association between SLE and environmental exposure to pesticides and inorganic compounds.

The study participants included 20 confirmed cases and 36 controls. In Nogales, Arizona, the prevalence of SLE found in phase I of this study was 20 cases per 19,849 people. or 103 cases per 100,000 population, approximately two to seven cases higher than the national prevalence. Income and employment did not differ significantly between cases and controls, except for educational level. Information on symptom severity obtained through three month diaries did not show any seasonal pattern in disease severity.

Toxicologic analysis showed that DDE and organophosphate metabolites were detected at elevated levels among cases and controls. Levels detected in both were higher than the reference mean or median for the U.S. population. However, the mean, median and frequency distributions for both cases and controls were remarkably similar, indicating no association between SLE and these chemical exposures. In addition, the univariate analysis demonstrated no statistical association between elevated levels of pesticides and disease status.

Investigation of Systemic Lupus Erythematosus, Nogales, Arizona (EPA)