Objectives

To describe the epidemiological characteristics of developmental delays (DD) at the national level and assess the changes over time.

Design

We calculated the incidence rates of DD from 2003 to 2016 and assessed the trends over time.

Setting

As dictated by law, local governments in Taiwan are required to register children with DD and provide services. The central government has constructed a national registry with the data from local centres. We analysed the national registry data.

Participants

We included children who were under 6 years old, and this population ranged from 1 164 150 to 1 577 443 per year during the study period. All registered cases were certified through a process set forth by law.

Primary and secondary outcome measures

We calculated annual incidence rates by age, sex and geographical area, and assessed trends over the study period.

Results

The incidence of DD in children under 6 years old displayed an increasing trend over the study period, ranging from 7.0 to 16.3 per 1000 person-years. Boys had higher incidence throughout all 14 years, and the boy-to-girl rate ratios had an increasing trend over time with some fluctuations, ranging from 1.84 (95% CI 1.77 to 1.92) to 1.99 (95% CI 1.93 to 2.06). In addition, rural areas had higher incidence rates, and the rural to urban rate ratios ranged from 0.98 (95% CI 0.94 to 1.03) to 2.00 (95% CI 1.94 to 2.06) without apparent time trends. Girls had a higher proportion of early reporting (<3 years) throughout all years, but the differences in the proportion of early reporting between rural and urban areas were not consistent.

Conclusions

Male sex appeared to be a risk factor for DD, which is unlikely to be due to more attention received by boys because girls had a higher proportion of early reporting. We also found that children lived in rural areas appeared to have a higher risk of having DD.