1. Introduction
Medical advances and improved health levels have led to an increase in life expectancy [1], followed by a dramatic increase in the global elderly population. Such a population inflammation initiated in the 20th century and continues in the 21st century, as the aging century of the world’s population [2]. The number of the elderly in 2000 was approximately equal to 600 million worldwide and it is estimated that the elderly will shape >20% of the world’s population by 2050 [3]. According to the United Nations Office, the population of the elderly aged ≥60 years in Iran will increase from about 8.2% in 2015 to 14.4% in 2030 and 31.2% in 2050 [4]. Spiritual health in old age is positively associated with various criteria of life satisfaction, modulates biopsychological health, and is beneficial in search of meaning and purpose in life; it presents a significant impact on mental health and success in this period [16]. Research has indicated that spirituality increases in old age. For example, Wink and Dillon (2002) conducted a longitudinal study and concluded that the level of spiritual health significantly increases from mid to late-life [17]. Studies suggested that spiritual forces in the elderly and patients lead to indescribable peace, strength, and vitality. Besides, the elderly patients with higher religious and spiritual beliefs encounter fewer cognitive problems [18, 19]. Iran is also experiencing the transition to an aging population and the number of elderly is on the rise. Therefore, there is a significant need for research to identify the predictors of successful aging concerning social policy. Moreover, due to limited studies on successful aging and spiritual health, the present study aimed to determine the predictability of spiritual health for successful aging.

2. Materials and Methods
The present descriptive-analytical study was conducted on the elderly in Qazvin City, Iran, in 2018. According to the research by Goli et al. (2016) entitled “the relationship between successful aging and spiritual health in the elderly in Tehran”, the sample size was determined by considering 95% confidence level (α=0.05) as 228 subjects. The final estimate of 290 subjects considered per 30% probability of non-response. Cluster sampling was performed in two stages; first, Qazvin City was divided into 5 regions (clusters), then, eligible samples were selected by convenience sampling method from each cluster. Initially, a list of public centers (e.g., mosques, parks, & daycare centers for the elderly) was prepared and a mosque and a park were selected from each cluster. Two daycare centers accepting members from all parts of the city were considered for sampling. The inclusion criteria of the study were the age of ≥60 years, the orientation of time, place, and person, ability to communicate verbally, and willingness to participate in the study. Moreover, presenting psychological conditions (Alzheimer’s disease & major depression disorder), difficulty in communicating, severe audiovisual impairments, and debilitating diseases included the exclusion criteria of the study. The required data were collected using a demographic information checklist, the Successful Aging Scale (SAS), and Paloutzian and Ellison Spiritual Wellbeing Scale.

3. Results
The study sample consisted of 291 elderlies with a Mean±SD age of 68.3±6.7 years and an age range of 60-87 years. In total, 162(57.7%) of the study samples were men. Most of the research participants were in the age group of 60-70 years (63.9%, 186 subjects), married (73.9%, 215 individuals), had ≥5 children (41.6%, 121 subjects), and lived with their spouse or children (70.4%, 205 individuals). The source of income of most of them was themselves (34.4%, n=100); the income level of most of them was moderate (42.3%, n=123); approximately one-third of the study subjects were illiterate (43%, n=121), and the majority of them were housewives or retired (35.7%, n=104). Furthermore, almost most of the study participants presented no history of hospitalization (54.6%, n=159). Regarding the history of physical illnesses, the majority of the study subjects reported a history of physical illness (81.1%, n=236) and only 5.8% (n=17) reported mental health illnesses. As per Table 1, the spiritual health of most of the examined elderly (81.1%) was at a strong level and their Mean±SD level of spiritual health equaled 87.68±15.37.

The results of stepwise regression analysis are demonstrated in Table 2.




In simultaneous regression analysis, all independent variables were entered into the analysis; beta values indicated the significance of the independent variables in predicting the regression equation. The collected results suggested that the independent variables entered in multivariate regression analysis could predict up to 44% of successful aging in the study participants.

4. Discussion and Conclusion 
Successful aging refers to the acquisition of individual potential and the optimal level of biopsychosocial ability through which the elderly feel satisfied with life. A characteristic that may be associated with successful aging is spiritual health [3]. This study aimed to determine the role of spiritual health in predicting successful aging. The present study results indicated that the spiritual health of 81.1% of the explored elderly was at a strong level. This finding was in line with those of most previous studies [22, 23]. The obtained data revealed a positive and significant relationship between spiritual health and successful aging. In another study, Islamic spirituality training positively influenced successful aging. In other words, the average score of successful aging in the intervention group was higher than that in the controls [25]. Additionally, the current research findings signified that improved religiosity and spiritual health declined the odds of mental distress and the feelings of despair and negative attitude on late-life stages in the examined elderly [26, 27]. Besides, the subjects who believed in the afterlife did not find life meaningless and hollow and were satisfied with their lives [28]. Moreover, spirituality plays a critical role in accepting crises; according to social nursing, human is a multidimensional being with the dimension of spirituality at the center [9].
The current study results revealed a significant relationship between spiritual health and successful aging. Besides, the existential health dimension was recognized as a predictor of successful aging. Therefore, to have successful aging for completing the final stages of lives with better health and optimal psychosocial functions, providing spiritual education programs and improving existential health (through managing psychosocial concerns and improving the relationship between the individual, society, & environment) can be effective. It is hoped that health policymakers take effective practical measures to improve spirituality in the elderly.

Ethical Considerations
Compliance with ethical guidelines
All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages. They were also assured about the confidentiality of their information and were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank the Vice Chancellor for Research of Qazvin University of Medical Sciences.

References