Introduction
In the recent century, according to the decreasing fertility rate and promoting health status and life expectancy, the proportion of older people has increased in most societies and aging has become an important global phenomenon [1]. In the advanced years of life, maintaining homeostasis is challenging for body systems [6]. As a result, the physiologic system of the body may become frail. Frailty syndrome is composed of sarcopenia, malnutrition, and chronic inflammation which is presented as weight loss, weakness, slow gait, low physical activity, and exhaustion. This can result in adverse outcomes, such as falls, delirium, and disability. In Iran, few studies have investigated the prevalence and related factors of frailty. This study determines the prevalence and associated factors of frailty in community-dwelling older adults covered by Shahid Beheshti University of Medical Sciences in Tehran City, Iran.

Methods
This cross-sectional study was performed on 383 older people aged 60 years and older, covered by healthcare centers of Shahid Beheshti University of Medical Sciences, Tehran, Iran in 2022. The participants were selected using random multistage cluster sampling. The covered healthcare centers were the North Health Network (consisting of 78 centers), the East Health Network (consisting of 73 centers), and Shemiranat Health Network (consisting of 23 centers). At first, 10% of the centers of each region were selected as clusters of the sampling; accordingly, 8, 8, and 3 clusters from North, East, and Shemiranat networks were respectively selected randomly. In each cluster, 20-21 participants were selected. The inclusion criteria were being 60 years old and older, not having cognitive impairment, and having the ability to communicate and answer the questions. Meanwhile, the exclusion criterion was incomplete questionnaires. In the next step, the Tilburg frailty indicator (TFI) items were asked of the participants by the researcher. Data analysis was done using the SPSS software, version 23. The prevalence of frailty among the participants was calculated. The chi-square test and the t-test were used for the relationship between frailty and other variables. In addition, logistic regression was used for multivariable analysis of the related factors as well. All the tests were considered significant at P<0.05. 

Results 
In this study, 383 older people with a mean age of 68.2±6.3 years participated. Among the participants, 187 people (48.8%) were female, 64 people (16.7%) were living alone, 277 people (72%) were married, 242 people (63.2%) had multiple chronic diseases, and 325 people (84.9%) were satisfied with their environmental status. About 40.5% of the participants (155 people) were frail. Frailty was significantly associated with age (P<0.003), lack of partner (P<0.001), low educational status (P<0.036), low income (P<0.012), unhealthy lifestyle (P<0.001), having multiple chronic diseases (P<0.001), and dissatisfaction with the environment (P<0.001). Among the stressful life events, the loss of loved ones, experiencing a serious illness (P<0.001), and a serious illness in beloved ones (P=0.037) were significantly related to frailty. In multivariate logistic regression (Table 1) having multiple diseases (odd ratio [OR]=1.754, P=0.034), dissatisfaction with environmental status (OR=2.035, P=0.032), having serious illness (OR=3.279, P=0.001), having unhealthy lifestyle (OR=11.61, P=0.005), and having no healthy/no unhealthy lifestyle (OR=3.115, P=0.001) had significant effect on odds of frailty.


Also, for each year of increasing age, the chance of vulnerability increases by 0.06.

Conclusion
The prevalence of frailty was 40.5% using the Tilburg frailty scale. Although the differences between measurement scales and the population type in different studies result in various prevalence rates, the results of this study showed a significant prevalence rate in comparison with other studies in the world and It needs more attention. Although the sampling was randomized, we invited older people to attend healthcare centers and frail older people were more likely to be unable to come. So the prevalence may be a bit lower than the real rate. It is also the same for omitting the people who had cognitive decline. The standard diagnostic tool for assessing the prevalence of frailty is comprehensive geriatric assessment but because There was not an available professional team, the Tilburg frailty scale was used to estimate an acceptable prevalence of frailty.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by Ethics Committee of Shahid Beheshti University of Medical Sciences, Tehran, Iran (Code: IR.SBMU.PHNS.REC.1400.110). 

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

Authors' contributions
All authors equally contribute to preparing all parts of the research.

Conflicts of interest
The authors declared no conflict of interest.


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