Association of Type 1 Diabetes With Month of Birth Among U.S. Youth
The SEARCH for Diabetes in Youth Study
- Henry S. Kahn, MD1,
- Timothy M. Morgan, PHD2,
- L. Douglas Case, PHD2,
- Dana Dabelea, MD, PHD3,
- Elizabeth J. Mayer-Davis, PHD4,
- Jean M. Lawrence, SCD, MPH, MSSA5,
- Santica M. Marcovina, PHD, SCD6,
- Giuseppina Imperatore, MD, PHD1 and
- for the SEARCH for Diabetes in Youth Study Group
- 1Division of Diabetes Translation, Centers for Disease Control and Prevention, Atlanta, Georgia;
- 2Department of Biostatistical Sciences, Division of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina;
- 3Department of Epidemiology, Colorado School of Public Health, University of Colorado Denver, Aurora, Colorado;
- 4Center for Research in Nutrition and Health Disparities, University of South Carolina, Columbia, South Carolina, and Department of Nutrition, University of North Carolina, Chapel Hill, North Carolina;
- 5Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California;
- 6Department of Medicine, University of Washington, Seattle, Washington.
- Corresponding author: Henry S. Kahn, hkahn{at}cdc.gov.
Abstract
OBJECTIVE Seasonal environment at birth may influence diabetes incidence in later life. We sought evidence for this effect in a large sample of diabetic youth residing in the U.S.
RESEARCH DESIGN AND METHODS We compared the distribution of birth months within the SEARCH for Diabetes in Youth Study (SEARCH study) with the monthly distributions in U.S. births tabulated by race for years 1982–2005. SEARCH study participants (9,737 youth with type 1 diabetes and 1,749 with type 2 diabetes) were identified by six collaborating U.S. centers.
RESULTS Among type 1 diabetic youth, the percentage of observed to expected births differed across the months (P = 0.0092; decreased in October–February and increased in March–July). Their smoothed birth-month estimates demonstrated a deficit in November–February births and an excess in April–July births (smoothed May versus January relative risk [RR] = 1.06 [95% CI 1.02–1.11]). Stratifications by sex or by three racial groups showed similar patterns relating type 1 diabetes to month of birth. Stratification by geographic regions showed a peak-to-nadir RR of 1.10 [1.04–1.16] in study regions from the northern latitudes (Colorado, western Washington State, and southern Ohio) but no birth-month effect (P > 0.9) in study regions from more southern locations. Among type 2 diabetic youth, associations with birth month were inconclusive.
CONCLUSIONS Spring births were associated with increased likelihood of type 1 diabetes but possibly not in all U.S. regions. Causal mechanisms may involve factors dependent on geographic latitude such as solar irradiance, but it is unknown whether they influence prenatal or early postnatal development.
Footnotes
-
The contents of this report are solely the responsibility of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention or the National Institute of Diabetes and Digestive and Kidney Diseases.
-
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
- Received May 14, 2009.
- Accepted August 6, 2009.
- © 2009 by the American Diabetes Association.
