Prevalence and sociodemographic correlates of antinuclear antibodies in the United States

Objective To estimate the prevalence, types, and sociodemographic and biobehavioral correlates of antinuclear antibodies (ANAs) in the US. Methods We conducted a cross‐sectional analysis of 4,754 individuals from the National Health and Nutrition Examination Survey 1999–2004. ANAs were assessed by indirect immunofluorescence. In ANA‐positive individuals, cellular staining patterns were determined, and specific autoantibody reactivities were assessed by immunoprecipitation. Results The ANA prevalence in the US population of individuals ages 12 years and older was 13.8% (95% confidence interval [95% CI] 12.2–15.5%). ANA prevalence increased with age (P = 0.01), and ANAs were more prevalent among females than males (17.8% versus 9.6%; P < 0.001), with the female‐to‐male ratio peaking at 40–49 years of age. ANA prevalence was modestly higher in African Americans compared with whites (age‐adjusted prevalence odds ratio [POR] 1.30, 95% CI 1.00–1.70). Remarkably, ANAs were less common in overweight and obese individuals (age‐adjusted POR 0.74) than in persons of normal weight. No significant associations of ANA with education, family income, alcohol use, smoking history, serum levels of cotinine, or C‐reactive protein were observed. In ANA‐positive individuals, nuclear patterns were seen in 84.6%, cytoplasmic patterns were seen in 21.8%, and nucleolar patterns were seen in 6.1%; the most common specific autoantibodies were anti‐Ro (3.9%) and anti‐Su (2.4%). Conclusion These findings suggest that more than 32 million persons in the US have ANAs, and that the prevalence is higher among females, older individuals, African Americans, and those with a normal body weight. These data will serve as a useful baseline for future investigations of predictors and changes in ANA prevalence over time.