Association of type 1 diabetes with month of birth among U.S. youth: The SEARCH for Diabetes in Youth Study.
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.


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.
Kahn
Henry S
HS
Division of Diabetes Translation, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. hkahn@cdc.gov
Morgan
Timothy M
TM
Case
L Douglas
LD
Dabelea
Dana
D
Mayer-Davis
Elizabeth J
EJ
Lawrence
Jean M
JM
Marcovina
Santica M
SM
Imperatore
Giuseppina
G
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D044469:Racial Groups / Q000706:statistics & numerical data; D012621:Seasons; D014481:United States / Q000453:epidemiology
Am J Clin Nutr. 2003 Dec;78(6):1128-34
14668274
Pediatrics. 2006 Oct;118(4):1510-8
17015542
Diabetologia. 2007 Jan;50(1):32-5
17093948
Med Hypotheses. 2008 Oct;71(4):604-5
18650028
Diabetologia. 2000 Sep;43(9):1083-92
11043853
Diabetologia. 2001 Oct;44 Suppl 3:B67-74
11724420
Diabetes Metab Res Rev. 2005 Jul-Aug;21(4):338-46
15852446
J Nutr. 2007 Feb;137(2):447-52
17237325
Diabetologia. 2005 Jul;48(7):1247-57
15971062
Diabet Med. 2000 Jan;17(1):59-63
10691161
Diabetologia. 2008 Aug;51(8):1391-8
18548227
JAMA. 2007 Jun 27;297(24):2716-24
17595272
J Pediatr Endocrinol Metab. 1998;11(3):461-4
11517963
Diabetes Care. 1998 Jan;21(1):190-1
9538991
J Pediatr Endocrinol Metab. 2004 Mar;17(3):289-96
15112905
Arch Dis Child. 1999 Aug;81(2):143-6
10490522
Diabetes Care. 2003 Dec;26(12):3237-42
14633808
Physiol Rev. 2005 Oct;85(4):1255-70
16183912
Diabet Med. 2001 Nov;18(11):939-40
11703443
J Pediatr Endocrinol Metab. 1999 May-Jun;12(3):397-402
10821219
Diabetologia. 2000 Sep;43(9):1093-8
11043854
J Pediatr Endocrinol Metab. 2002 May;15(5):645-7
12014524
J Am Acad Dermatol. 2007 Oct;57(4):588-93
17637484
J Endocrinol. 2004 Apr;181(1):11-23
15072563
Lancet. 2001 Nov 3;358(9292):1500-3
11705562