1. Introduction
Increased life expectancy, lower mortality, lower birth rates and improved health care have led to the occurrence of aging phenomenon in societies [1]. In Iran, the phenomenon of population aging has not only begun, but also its acceleration is very high due to the rapid decline in birth rates over a short period of time [6]. Health care is one of the basic needs of the elderly people who are the most popular group that receive these services. On the other hand, most health care needs of the elderly are very costly in the elderly due to prolonged hospitalization, periodic rehabilitation services, and low self-care ability [7-9]. The households with elderly members may therefore have serious economic problems in providing for medical needs for them, or may have to devote a greater share of household income to health costs, resulting in devastating health expenditure [14]. Therefore, the rapid growth of the elderly population in Iran and the meeting their health care expenditures can cause many economic problems in national and household levels in the near future [15]. Hence, this study aims to evaluate the effect of the presence and age of elderly members on health care costs of the households in Iran.
2. Materials and Methods
This study is a secondary analysis using 2016 national household, expenditure and income survey data. Sample size was 19337 households in rural areas and 18809 households in urban areas (total=38146) in Iran. The “total health care expenditure” and “medical expenses” of the households were dependent variables, and the variables of “presence of an elderly member in the household” and “age of elderly members in the household” are the main independent variables. Other contextual variables included: Place of residence (urban or rural areas), health development rate of the province of residence, presence of a smoker in the household, insurance, home ownership, household head education, household size, and household income. Linear multiple regression analysis was used to analyze the data using 4 models; In the first two models, the relationship between the age of elderly members in the household with different age groups and in the next two models, the relationship between the presence or absence of an elderly member in the household with total health care expenditure and medical expenses were investigated. Data analysis was conducted in STATA V. 14 software.

3. Results
There was a significant association between the presence of an elderly member in the household and increase in total health care expenditure and medical expenses, such that for one increase in the age of elderly members, total health care expenditure increased by 390,000 Tomans, and medical expenses increased by 195,000 Tomans. In terms of age, families with an elderly member aged 75-79 years incurred the highest care costs compared to other age groups. Moreover, household income, having health insurance, having a smoker member, place of residence (urban areas), household head education, and health development rate of the province of residence had significant association with total health care expenditure and medical expenses of households. However, no association was found between having an income-earner member and total health care expenditure/medical expenses. The obtained F value presented in Table 1, confirms the strong relationship between the independent variables of this study with the dependent variables. 
4. Conclusion
Based on the findings of this study and considering that the presence of an elderly member contributes significantly to the increase of household health care costs, future policies need to be designed to support these households, especially those with older members. The findings of this study indicated higher health care costs paid by households with higher socioeconomic status than those with lower status, which was quite expected because low-educated and low-income households have less purchasing power and therefore, their health costs have been significantly lower. Hence, policies to support households with elderly members, and poorer or deprived households should be prioritized. Empowering the elderly people, expanding home care, providing health counseling and public education, and promoting self-care can improve the health of these people and economically prevent further health-related costs. Future studies should address supportive strategies and policies for the households with elderly members or explore ways to reduce health care costs in these households.
Ethical Considerations
Compliance with ethical guidelines
This study was a secondary analysis using 2016 national household, expenditure and income survey data. So, no ethical approval was required.

Funding
This study received no financial support from any organization.
Authors' contributions
All authors had contribution in preparing this paper.
Conflicts of interest
The authors declare no conflict of interest
Acknowledgements
The authors would like to thank Statistical Centre of Iran for making data available and all those helped in conducting this study.