The needs of outpatient services, a key accessible health resource, are increasing in an increasingly aging population in China. So rational allocation of outpatient service resources to meet older people's health needs is a key to improving their health level.

To explore the factors affecting the utilization of outpatient services in the elderly, to provide feasible suggestions for improving older people's health level and the allocation of medical resources.

This study was conducted in 2021 using the data of older people (≥60 years old) attending the CHARLS 2018. The number of using outpatient services in these people in the past month prior to the CHARLS 2018 and associated factors were studied using a system developed based on the framework of Anderson's Behavioral Model of Health Services Use, with sex, age, marital status, the type of hukou (rural or urban), education level, smoking and drinking were classified as predisposing factors, health insurance, monthly household income per capita and the average distance from home to medical institutions as enabling factors, and chronic disease prevalence and self-rated health as need factors. The zero-inflated negative binomial regression (ZINB) was used to identify factors associated with the use of outpatient services.

In all, 9 551 older people were included for analysis. Among them, non-users of outpatient services in the past month numbered 8 038 (84.16%), and one-time, two-time, and three or more-time users numbered 749 (7.84%), 367 (3.84%), and 397 (4.16%), respectively. The number of using outpatient services differed statistically by the type of hukou, education level, smoking, drinking, health insurance prevalence, monthly household income per capita, chronic disease prevalence, and self-rated health status (P<0.05). The results of Logit regression model (one part of the ZINB) in fitting the data indicated that older age, high school education or above, having health insurance, suffering from a chronic disease and poor self-rated health were associated with increased probability of utilizing outpatient services (P<0.05). And the results of negative binomial count model in fitting the data indicated showed that the age of 70-74 years was associated with decreased probability of utilizing outpatient services, while an average distance of greater than 1 km but less than 10 km between home and medical institutions, and three types of self-rated health (good, poor and very poor) were associated with increased probability of utilizing outpatient services (P<0.05) .

Our study indicates that the use of outpatient services was insufficient in these older people, which was associated with predisposing, enabling and need factors. To improve this, it is suggested to rationally strengthen the provision of outpatient services to vulnerable groups with underuse of such services and individuals with needs of high-quality services. In addition, attention should be given to chronic disease management and self-rated health of the elderly to improve their awareness and level of health management.