Yvette C. Cozier

Sarcoidosis is a granulomatous inflammatory disease with unknown etiology. Epidemiological studies have contributed greatly to our knowledge about sarcoidosis, providing critical information on the determinants and distribution of the disease. In this review, we summarize recently published findings from epidemiological studies on sarcoidosis. We review the epidemiological tools used, the incidence and prevalence of disease, mortality and cancer risk after sarcoidosis and nongenetic risk factors for sarcoidosis. Genetics studies have not been included as they deserve a separate review. Leveraging existing epidemiological data to conduct etiological studies aimed towards understanding and preventing disease is critical for future sarcoidosis research.

PURPOSE OF REVIEW: The aim of this review is to describe the latest studies on sarcoidosis incidence, prevalence and risk factors with a special focus on reports in the last 2 years. The potential biases affecting these studies are discussed. RECENT FINDINGS: The prevalence and incidence of sarcoidosis vary greatly depending on region of the world. Variations in data sources and settings can affect estimates of the burden of sarcoidosis, sometimes making them difficult to compare across countries. It is not well understood how the distribution of sarcoidosis phenotypes differs across populations. Age, sex and race are the most important sources of variation in incidence and prevalence. Recent epidemiological studies provide new insights on the role of genetic and nongenetic risk factors for sarcoidosis. SUMMARY: High-quality and systematically collected data, with depth (detailed information per individual) and breadth (many individuals), is needed to further understand the complexity and heterogeneity of sarcoidosis.

The authors examined the relation between individual and neighborhood socioeconomic status (SES) and type 2 diabetes incidence among African-American women in the prospective Black Women's Health Study. Participants have completed mailed biennial follow-up questionnaires since 1995. US Census block group characteristics were used to measure neighborhood SES. Incidence rate ratios were estimated in clustered survival regression models. During 12 years of follow-up of 46,382 participants aged 30-69 years, 3,833 new cases of type 2 diabetes occurred. In models that included both individual and neighborhood SES factors, incidence rate ratios were 1.28 (95% confidence interval: 1.15, 1.43) for < or = 12 years of education relative to > or = 17 years, 1.57 (95% confidence interval: 1.30, 1.90) for household income <$15,000 relative to >$100,000, and 1.65 (95% confidence interval: 1.46, 1.85) for lowest quintile of neighborhood SES relative to highest. The associations were attenuated after adjustment for body mass index, suggesting it is the key intermediate factor in the pathway between SES and diabetes. The association of neighborhood SES with diabetes incidence was present even among women who were more educated and had a higher family income. Efforts to reduce the alarming rate of diabetes in African-American women must focus on both individual lifestyle changes and structural changes in disadvantaged neighborhoods.

Perceived discrimination may contribute to somatic disease. The association between perceived discrimination and breast cancer incidence was assessed in the Black Women's Health Study. In 1997, participants completed questions on perceived discrimination in two domains: "everyday" discrimination (e.g., being treated as dishonest) and major experiences of unfair treatment due to race (job, housing, and police). Cox proportional hazards models were used to estimate incidence rate ratios, controlling for breast cancer risk factors. From 1997 to 2003, 593 incident cases of breast cancer were ascertained. In the total sample, there were weak positive associations between cancer incidence and everyday and major discrimination. These associations were stronger among the younger women. Among women aged less than 50 years, those who reported frequent everyday discrimination were at higher risk than were women who reported infrequent experiences. In addition, the incidence rate ratio was 1.32 (95% confidence interval: 1.03, 1.70) for those who reported discrimination on the job and 1.48 (95% confidence interval: 1.01, 2.16) for those who reported discrimination in all three situations - housing, job, and police - relative to those who reported none. These findings suggest that perceived experiences of racism are associated with increased incidence of breast cancer among US Black women, particularly younger women.