Objectives The impact of population aging on health expenditure is inevitable. The effects of aging on healthcare costs can be detected by assessing changes in individuals' health and demand for healthcare. In this study, we aim to investigate the age and sex distribution of the hospital admission rate and hospital costs. We also compare the cost spent on 19 groups of hospital services and length of hospital stay between elderly and non-elderly groups.
Methods & Materials This is a quantitative, descriptive-analytical study with a cross-sectional design conducted on data of 41 million people insured by Iran Health Insurance Organization in 2020. Hospital admission rate, length of stay, and hospital costs were response variables. Costs (In Iranian Rials) included insurance payments, patients' out-of-pocket spending, and government subsidies. The USD exchange rate in 2020 was 42173.8744 Iranian Rials (IRR). Age and sex of the patients, ownership of the hospital, type of hospital registration, and the received services were descriptive variables. The Mann-Whitney U test was used to compare costs between elderly and non-elderly groups, and between females and males. Spearman's correlation test was used to examine the relationship between age and response variables. 
Results During the study period, there were about 3,800,000 hospital admissions. The rate of hospital admission in the elderly was 3.7 times higher than in non-elderly groups. The average length of stay was 1.3 days for the elderly patients, and 2.2 days for non-elderly (<60 years) patients. Among the elderly, men had a higher hospital admission rate than women, while in non-elderly people, women had a higher admission rate. The number of patients <60 years was 2.3 times that of patients >60 years. However, the average cost for each patient <60 years was 28 million IRR and the average cost for patients > 60 years was 45 million IRR. The average costs of surgery, medicine and medical supplies for older patients was 1.5 times more than that for people <60 years. Men generally had longer hospital stays and higher average costs. There was a positive and significant relationship between the hospital admission rate and the age of patients (r=0.879, P<0.001). As the age of patients increased, their length of hospital stay increased significantly (r=0.582, P<0.001). The relationship between the patient's age and the average hospital costs was also positive and significant (r=0.582, P=0.006).
Conclusion Hospital admission rate, length of hospital stay, and average hospital costs are significantly higher among older adults insured by Iran Health Insurance Organization.