Anthropometric measurements and mortality in frail older adults
Introduction
In addition to the growing demand of health care services by older adults, a specific subgroup of this age group particularly burdens the system, especially when not properly managed: the frail older adults (Cesari et al., 2016b). Although there remains controversy (Bergman et al., 2007; Hogan and others, 2003) as to a precise definition or clinical characterization of frailty, it is generally accepted that when frailty remains undetected, the risk of an acceleration in the functional decline of an older adult increases exponentially, such that, even minimal stressors, may trigger catastrophic outcomes (Aalen et al., 2014; Cesari, 2011), including death. Thus, in spite of a lack of precision in its definition, it is important to seek indicators of enhanced mortality risk in frail elders in order to implement adapted care models which target the multidimensional and heterogeneous complexity of these individuals (Cesari et al., 2016a).
Anthropometric measurements are commonly used in clinical practice; in particular, body mass index (BMI) is widely accepted and used in these settings (Dent et al., 2015). In recent years, such assessments have strongly supported the risk stratification of an individual for adverse cardio-metabolic outcomes and any-cause mortality (Kim et al., 2015). However, when it comes to frail older adults, results of these anthropometric measures are often misleading (Oreopoulos et al., 2009; Zunzunegui et al., 2012).
Indeed, there is an ongoing debate regarding the role of BMI and, for example, its alleged U-shape relationship with mortality in older adults (Hubbard et al., 2010; Zunzunegui et al., 2012). In particular, there is a lack of evidence as to how this measure may work in the prediction of mortality risk in frail older adults. Moreover, other anthropometric measures of similar interest, such as waist-to-hip ratio [WHR] or calf circumference [CC], have little literature to their name (Landi et al., 2014; Welborn et al., 2003), even though they could also be potentially used for risk stratification.
Understanding the role that anthropometric measures may have in the risk stratification of frail elders is crucial (Abellan van Kan et al., 2008), especially in low and medium income countries where a more sophisticated initial screening may not be feasible. As easy-to-administer screening and assessment tools are particularly needed (Elder, 2013), such measurements could provide simple tests which can be quickly carried out by a healthcare professional in any consultation and which would be particularly useful in settings where human resources specialized in older adult healthcare are scarce (Gutierrez-Robledo, 2002).
The aim of this study is to determine which anthropometric measurement (BMI, knee-adjusted height BMI, WHR and CC), better predicts mortality in a group of older Mexican adults. We hypothesize that BMI will not be as good a mortality predictor as it is in non-frail older adults, and, further, that calf circumference and/or WHR will be better mortality predictors in frail older adults.
Section snippets
Design
The Mexican Health and Aging Study (MHAS) is based on a cohort of older adults aged ≥50-years with a follow-up of 14 years. The sample was designed to be representative of the whole country. Households were qualified to be in the sample if they contained at least one 50-year or older person; they were then invited face to face, and if they accepted, an appointment was made to perform the interview at home. The full description, objectives and database of the MHAS are available to the public (
Cohort demographic assessment
Of the 1298 adults in the sample, the average age was 62.08, with survivors having a lower average age than those who died. The sample contained 819 women (63.1%) and 479 men (36.9%), which is consistent with the proportions found in other Mexican based health questionnaire studies (Easton et al., 2017a, Easton et al., 2017b). Other demographic variables considered were: Marital status, living environment, education, smoking status, physical activity and number of comorbidities. A summary of
Discussion
According to our results, the widely-used BMI measurement (in both its knee-adjusted and normal versions) is not useful in categorizing those frail older adults with a higher risk of dying. In addition, WHR was not useful either, once the considered covariates were taken into account. However, a low CC was shown to be associated with higher risk of mortality. To our knowledge, this is the first work to address the use of anthropometric measurements to categorize mortality risk in frail older
Conclusions
As per previous studies contrasted with our results, frail older adults, a complex and at-risk segment of the population, require care that differs from their non-frail counterparts. Anthropometric measurements have different significance in frail older adults, and these differences could have implications on adverse outcomes. As the interpretation of anthropometric measurements may have different connotations in frail older adults, they should be interpreted cautiously before taking action,
Conflicts of interest
None declared.
Funding
The Mexican Health and Aging Study was partially funded by NIH R01 AG018016 (PI Rebeca Wong). The manuscript was supported by CONACYT Fronteras grant FC-2015-2/1093.
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