The majority of newly diagnosed type 1 diabetes cases in China are diagnosed in adulthood, researchers said.
The population-based study identified 5,018 new cases of type 1 diabetes among a Chinese cohort followed from 2010 to 2013 — 65.3% of whom were diagnosed at age 20 or older, reported Jianping Weng, PhD, of The Third Affiliated Hospital of Sun Yat-Sen University in Guangzhou, China, and colleagues.
Still, estimated incidence of type 1 diabetes was highest among those 14 and younger (incidence 1.93 per 100,000, 95% CI 0.83-3.03), appearing online in The BMJ.
Point estimates for the incidence of newly diagnosed type 1 diabetes tapered off among older age groups: 1.23 per 100,000 person years at 15-29 (95% CI 0.45-2.11) and 0.69 among those 30 and older (95% CI 0.00-1.51).
“[M]ost epidemiological studies of type 1 diabetes focused on childhood onset type 1 diabetes. Although type 1 diabetes most often develops in children, it can occur at any age,” the group wrote. “Our previous study also indicated that the onset of type 1 diabetes in adulthood is not rare in China. Yet little is known about its incidence in adults aged more than 20 years,” Weng’s group added.
These findings echo the results of another recent study from the U.K., which found roughly 42% of people with type 1 diabetes were diagnosed between 31 to 60 years of age.
Weng’s group analyzed nearly 10% of the Chinese population, spanning 13 areas in China with 505 hospitals. Type 1 diabetes was diagnosed using American Diabetes Association and the World Health Organization criteria by endocrinologists and/or pediatricians.
The overall estimated incidence among all age groups across China was 0.93 per 100,000 person years (95% CI 0.90-0.95). This was also slightly higher among males compared to females (0.95 for males, 95% CI 0.91-0.99, vs 0.81 for females, 95% CI 0.78-0.85, P<0.001.)
However, among the youngest age group of 0 to 14 years, females had a significantly higher estimated incidence of type 1 diabetes compared to males (2.21 for females, 95% CI 2.05-2.39 versus 1.72 for males, 95% CI 1.58-1.86, P<0.001).
For newly diagnosed cases, those 0 to 14 years of age were more commonly had the following clinical characteristics with the onset of type 1 diabetes:
- Immediate initiation of insulin: 98.4% (0-14 years) versus 91.5% (≥30 years)
- Diabetic ketosis <6 mo. of diagnosis: 92.9% versus 83.8%
- Diabetic ketoacidosis <6 mo. of diagnosis: 51.4% versus 30.8%
- ≥1 positive result for diabetes autoantibody <6 mo. of diagnosis: 73.5% versus 55.4%
A fasting C peptide of 0.2 ng/mL or higher at the onset of type 1 diabetes was slightly more common among the older age group (27.5% for those 30 and older versus 22.5% at age 10-14).
Compared to the similar DiaMond study conducted in China back in 1998, incidence of type 1 diabetes among those under 15 years of age has risen 3.8-fold — “equal to a roughly 6.5% annual increase,” the group wrote. The prior study estimated the incidence of type 1 diabetes in this age group to be 0.51 per 100,000 person years in 1985-1994.
“Our study confirms that the incidence of type 1 diabetes remains low in China, even after a 3.8-fold increase of what was reported by the DiaMond Project two decades ago,” they highlighted, adding, “Although the underlying mechanism is not completely known, the low incidence in China is probably attributed to genetic, environmental, and behavioural factors.”
Click here for the American Association of Clinical Endocrinologists’ clinical practice guideline for developing a diabetes mellitus comprehensive care plan.
The study was funded by the China International Medical Foundation, national key R&D programme of China, and National Natural Science Foundation of China.
None of the authors reported any relevant conflicts of interest.