Epidemiology of Sarcoidosis in a Prospective Cohort Study of U.S. Women

Abstract

Rationale: Sarcoidosis is a systemic granulomatous and inflammatory disorder that most often involves the lungs but also affects many other organs. Data on sarcoidosis from large epidemiological studies remain scarce.

Objectives: To evaluate the baseline prevalence and 22-year incidence of sarcoidosis and their associations with demographic and geographic characteristics in a large cohort of U.S. women.

Methods: The Nurses' Health Study II is a prospective cohort study of U.S. female nurses enrolled in 1989 (aged 25-44 yr, n = 116,430). Data on major illnesses were collected through biennial questionnaires (1989-2011). Cases were identified by the nurses' self-report of physician-diagnosed sarcoidosis. Associations of demographic and geographic characteristics with sarcoidosis were evaluated by logistic regression and Cox models.

Measurements and main results: A total of 377 sarcoidosis cases were identified. The baseline prevalence was 100/100,000 women. The average annual incidence rate was 11/100,000 during 2,275,028 person-years of follow up. Incidence rate increased with age (P = 0.003), from 9 to 15/100,000 in women aged less than 35 to 55 or more years, respectively. Black women had a higher prevalence (odds ratio, 5.24; 95% confidence interval, 2.87-9.55) and incidence (hazard ratio, 3.80; 95% confidence interval, 2.31-6.24) than white women. Across U.S. regions, more than twofold differences were observed in sarcoidosis prevalence and incidence, with consistently higher rates in the Northeast.

Conclusions: We provide recent national data on the epidemiology of sarcoidosis among U.S. women. Important differences in prevalence and incidence were observed across U.S. regions. Large epidemiological studies are needed to better understand the causes of the observed demographic and geographic differences in sarcoidosis.

Keywords: epidemiology; incidence; lung diseases; prevalence.

Figure 1.

Age-specific incidence rate of sarcoidosis in women, Nurses’ Health Study II (n = 261 incident cases; 2,275,028 person-years). Similar results were observed in sensitivity analyses where (1) cases were restricted to participants who specifically indicated that the diagnosis of sarcoidosis occurred within 2 years before the questionnaire cycle where they first reported sarcoidosis (n = 163 incident cases; 2,274,204 person-years), (2) women with less frequent medical examination (as measured by the number of times participants reported having had physical examination during follow up) were excluded (analysis conducted with n = 223 incident cases and 1,828,972 person-years), and (3) women who returned fewer than eight biennial follow-up questionnaires (out of 11) were excluded (analysis conducted with n = 236 incident cases and 2,076,332 person-years).