Low physical activity is the strongest factor associated with frailty phenotype and frailty index: data from baseline phase of Birjand Longitudinal Aging Study (BLAS)

Background

Frailty is the most complicated expression of aging that is related to disability or multi-morbidity, but it is utterly distinct from them as it is a complex and dynamic process with different aspects of the intervention [1]. Indeed, frailty is a spectrum reflecting the biological age/intrinsic capacity of humans. On the other word, frailty is the end of the “healthy aging” spectrum [1, 2].

It is noteworthy that frailty is an important predictor of multiple adverse outcomes, including disability, hospitalization, institutionalization, premature death, and low resistance to stressors [3]. This means that a similar stressor can have different consequences in a frail individual compared to a robust person [3]. According to observations, the level of frailty is a good predictor or selection criterion for treatment or intervention [4]. Hence, diagnosing frailty in the early stages is critical for preventing or delaying the onset of late-life disability and its adverse outcomes [5].

There are more than 30 assessment tools to measure frailty; however, there is no consensus on a gold standard definition for frailty, which results in differences in estimating the frailty prevalence [6]. The two most frequent tools for diagnosing frailty are the frailty phenotype (FP) and frailty index (FI) [7]. FP only considers physical markers. It is operationalized as a syndrome that includes the five following characteristics: unintentional weight loss, muscle weakness, slow walking speed, low physical activity, and exhaustion [8]. Another approach is the FI, which was developed by Rockwood et al. as a risk index by counting the number of deficits accumulated over time. It includes diseases, physical and cognitive impairments, psychosocial risk factors, and common geriatric syndromes other than frailty [9].

The prevalence of frailty in older adults varies according to the definition, setting, and country. The global prevalence of frailty in population 65 years and older is 10.7% [2]. On the other hand, according to a systematic study in people aged ≥50 years old and in 62 countries, the prevalence of frailty index was 24% (26–22%) and the prevalence of frailty phenotype was 12% (13–11%) [2]. The prevalence of frailty is 12–13.5% in Asia according to the FI instrument and 1.5–18.3% according to the FP instrument [10–14]. Considering the strong association between frailty and other poor health outcomes such as disability, dependency, multi-morbidity, and death, determining the prevalence of frailty and its associated factors in different communities plays an important role in health policy-making [15, 16].

Very few studies have investigated the prevalence of frailty in Iran. A study in Tehran found an age unstandardized prevalence of 60% for frailty. Another study in five cities in the southwest of Iran reported frailty prevalence measured by FI of 14.3% [17, 18]. However, to the best of our knowledge, none of the studies in |Iran compared the prevalence of frailty based on different definitions. Moreover, we could not find any data regarding the prevalence of frailty in rural areas. Therefore, this study was conducted to determine frailty prevalence measured by FP and FI and their associated factors in the community-dwelling older adults (≥ 60) in the rural and urban areas