Introduction
The aging population poses a global challenge. Recently, there has been a rising concern about the increasing prevalence of older people suffering from several chronic diseases at the same time. Such concerns have led to the enhancement of national programs aimed at improving the health, function, and quality of life of older people in Iran. In this regard, a national plan titled “integrated geriatric care program” (IGCP) is currently being implemented by the Iranian Ministry of Health and Medical Education in healthcare centers across Iran. In this plan, the risk factors and key clinical symptoms have been used for early diagnosis, appropriate treatment, and timely referral. 
Although healthcare services are being provided to older adults in Iran, there are still many challenges in terms of structure, specialized organizational resources, and service delivery. The evaluation of these service delivery program can help assess the current status, identify service delivery gaps and the areas for improvement. On of the theoretical framework for this purpose is called the reach, effectiveness, adoption, implementation, and maintenance (RE-AIM) model. The use of this model is reported to be suitable for those in the fields of geriatric care, public health, and related disciplines. This study aims to evaluate the IGCP in Yazd City, Iran, based on the RE-AIM model.

Methods & Materials 
This is a cross-sectional study conducted at Imamshahr Health Center in Yazd in 2023. Data collection was conducted in two phases. In the first phase, all program indicators from 2016 to 2022 were extracted from the electronic health records of 1,672 older adults covered by the mentioned health center. Then, the obtained data were categorized according to the five dimensions of the RE-AIM model. In the second phase, supplementary information was collected using a researcher-made questionnaire from all healthcare providers at the mentioned health center (n=9). The researcher-made questionnaire was developed by the research team based on the IGCP booklet. It had five sections based on the five dimensions of the RE-AIM model. The results of the expert panel assessments affirmed the adequate validity and reliability of this questionnaire (CVR=0.98, CVI=0.97, Cronbach’s α=0.878).
Data analyses were performed in SPSS software, version 26. Data preprocessing was done to identify outliers and missing values and the normality of data distribution was tested. Friedman test was used to determine the difference between standardized scores of the five evaluation dimensions. The significance level was set at 0.05. The trend of changes in indicators was analyzed using time-series models from 2016 to 2022, followed by forecasting these indicators for 2023. The time-series analysis and forecasting were conducted using the auto regressive integrated moving average (ARIMA) model based on the available data (indicators from 2016 to 2022), employing the Forecast Package and selecting the auto.arima function in R software, version 4.2.2.

Results
First phase
To determine the effects of implementing the IGCP, the trend of changes in the indicators from 2016 to 2022 was plotted. The indicators of care for blood pressure, depression, falls, and nutrition showed that 508, 427, 459, and 470 older people had received these types of care in 2023, respectively. The total number of covered older adults reached 2,780 people in 2022. The highest number of older people participating in group education classes was 44 in 2019. The number and percentage of total care reached 427 people and 15.4% in 2022, respectively.
The forecast value for the total number of covered older adults for 2023 was 2788 (95% CI, 2573.99%, 3002.01%). The number of total care for 2023 was predicted to be 189.29 (95% CI, 43.22%, 421.79%). The values obtained for the total number of covered older adults and the number of total care in 2023 were 2,855 and 571 persons, respectively, which aligns with the forecast values.

Second phase
In the second phase, 9 healthcare providers (5 female and 4 male) with a mean age of 39.11±9.22 years participated. The participants included two physicians, five public health experts, one psychologist, and one nutritionist who responded to the researcher-made questionnaire. Based on the results presented in Table 1, the mean scores were 34.26±15.28 for reach, 49.51±12.08 for effectiveness, 58.64±32.41 for adoption, 72.11±9.98 for implementation, and 55.71±12.26 for maintenance.


As can be seen, the highest and lowest scores were related to the dimensions of implementation and reach, respectively. According to 66.7% of healthcare providers, the IGCP had unfavorable performance based on the reach dimension. From the perspective of 66.7%, the program had relatively favorable performance in the implementation dimension. Overall, 77.8% of healthcare providers considered the program to have relatively favorable performance. The Friedman test results indicated a statistically significant difference between the scores of different RE-AIM model dimensions (P=0.002). 

Conclusion
Overall, the IGCP implementation at Imamshahr Health Center in Yazd is relatively favorable. Based on the reach domain of the RE-AIM framework, the participation of older adults in the program was weak. Therefore, there is a need for necessary actions to improve the participation of older adults in the future. This study provides valuable information that can be a basis for evaluating other programs in primary healthcare. Our findings highlight the importance of aligning the health service delivery programs with the predetermined organizational goals to improve the program implementation. Furthermore, the results of this study provide policymakers and health managers of geriatric care programs in Iran with insights for better decision-making and planning in the future.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Research Ethics Committee of Tabriz University of Medical Sciences, Tabriz, Iran (Code: IR.TBZMED.REC.1401.100). 

Funding
This article was extracted from the dissertation of Neda Sadat Nazaripanah, funded by Tabriz University of Medical Sciences, Tabriz, Iran (Grant No: 68748). 

Authors' contributions
Conceptualization and methodology: Neda Sadat Nazaripanah and, Haidar Nadrian; Validation: Neda Sadat Nazaripanah and, Neda Gilani; Data analysis: Neda Sadat Nazaripanah, Haidar Nadrian and, Neda Gilani; Investigation, editing & review: Neda Sadat Nazaripanah, Haidar Nadrian and, Mina Hahsemiparast; Initial draft preparation: Neda Sadat Nazaripanah; Visualization: All authors; Supervision: Neda Sadat Nazaripanah and , Haidar Nadrian; Project administration, resources, and funding acquisition: Haidar Nadrian.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgments
The authors would like to thank the Deputy for Research and Technology of Tabriz University of Medical Sciences for the financial support and the personnel of Imamshahr Health Center in Yazd city and all participants for their cooperation.