Residual beta-cell function and male/female ratio are higher in incident young adults than in children: the registry of type 1 diabetes of the province of Turin, Italy, 1984-2000.
OBJECTIVE
The hypothesis of age-dependent variations in epidemiologic and clinical features at onset of type 1 diabetes has been assessed in the registry of the province of Turin, Italy.


METHODS
The study base is the population 0-29 years of age of the province of Turin, in the period from 1984 to 2000. Islet cell antibody (ICA), GAD antibody (GADA), antibodies to protein tyrosine phosphatase (IA2), and C-peptide were measured in subgroups of the cohort.


RESULTS
One thousand fifty-six incident cases have been identified (completeness of ascertainment 98.1%). Rates per 100,000 person-years were similar in males and females in the age-group 0-14 years (10.7, 95% CI 9.5-12.0 vs. 9.8, 8.6-11.1). In the age-group 15-29 years, males had higher risk than females (7.7, 6.9-8.6 vs. 5.3, 4.6-6.1; rate ratio, 1.46, 95% CI 1.23-1.74; P = 0.00002). Fasting plasma C-peptide values (n = 575) were twofold lower in the age-group 0-14 years than in the age-group 15-29 years (0.10 vs. 0.23 nmol/l; P < 0.0001). Frequencies of ICA and IA2 positivities (n = 183) decreased with increasing age, whereas frequency of GADA positivity increased. Idiopathic cases were 12.6% and had higher mean values of fasting (0.28 vs. 0.14 nmol/l; P = 0.043) and stimulated C-peptide (0.59 vs. 0.34 nmol/l; P = 0.05). In logistic regression analyses, subjects with fasting C-peptide values in the upper quartile had higher likelihood of being older (odds ratio 1.20 for year, 95% CI 1.11-1.28), ICA negative (0.26, 0.10-0.70), and female (1.29, 0.48-3.42).


CONCLUSIONS
This study shows 1) sex differences in incidence rates in young adults; 2) better preserved beta-cell function in young adults, in idiopathic cases (12%), and in ICA-negative cases; and 3) lower frequencies of ICA and IA2 positivities and higher frequency of GADA positivity in young adults than in children.
Bruno
Graziella
G
Department of Internal Medicine, University of Turin, corso Dogliotti 14, I-10126 Turin, Italy. graziella.bruno@katamail.com
Cerutti
Franco
F
Merletti
Franco
F
Cavallo-Perin
Paolo
P
Gandolfo
Enrico
E
Rivetti
Marina
M
Runzo
Cristina
C
Pinach
Silvia
S
Pagano
Gianfranco
G
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D015551:Autoimmunity; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007515:Islets of Langerhans / Q000502:physiology*; D007558:Italy / Q000453:epidemiology; D008297:Male; D012042:Registries; D012307:Risk Factors; D012727:Sex Characteristics; D017678:Sex Distribution