Age-related sensory impairments, specifically, vision or hearing impairment, are associated with decreased physical (Swenor et al., 2015; Chen et al., 2015), cognitive (Swenor et al. 2019; Lin et al., 2013), and psychosocial function (Evans et al., 2007). Older adults with sensory impairment are also at an increased risk of negative health outcomes including mortality (Christ et al., 2014; Karpa et al, 2010). The interaction between sensory impairment and function is also reflected in the increased prevalence of physical frailty among those with sensory deficits. Analyses of the NHANES data in the US (Kamil et al., 2014) and a recent systematic review and meta-analysis of cross-sectional studies have all reported that the presence of vision or hearing impairment was associated with a 1.5 to 2-fold greater odds of pre-frailty and 2.5 to 3-fold greater odds of physical frailty, respectively (Tan et al., 2020). It is important to emphasize that this relationship is found with the physical frailty phenotype and is not just a function of increased co-morbidities as assessed by deficit accumulation indexes.
Impact of Sensory Impairment on Frailty
Sensory impairment predicts the development of physical frailty. Longitudinal studies suggest that both vision and hearing impairment increase the odds of frailty progression from baseline robustness. The Women’s Health and Aging Studies showed that older adults with visual impairment are more likely to progress toward frailty, with a 3.5-fold greater odds of incident frailty over 3 years, than those who are unimpaired, establishing temporality of this relationship (Swenor et al., 2019). Similarly, the English Longitudinal Study of Ageing found that self-reported hearing loss was associated with 1.4-fold greater odds of incident prefrailty or frailty over 4 years (Liljas et al., 2017).
The precise mechanisms underlying the sensory impairment – physical frailty relationship remain unclear, but the longitudinal data suggest that sensory impairment could be a causal risk factor for frailty. One possible pathway is through the negative impact on function. Sensory impairment contributes to decreased cognitive resources, walking speed, social isolation and depression, leading to aggregate physiological dysfunction and thus to developing physical frailty (Tan et al., 2020 ;Fried et al, 2009). Alternatively, the association could be non-causal in nature, indicating instead a shared underlying pathological pathway. For example, inflammation, microvascular diseases and neurodegeneration might lead to both sensory loss and frailty (Tan et al., 2020; Liljas et al., 2017).
Applying Knowledge of Frailty to the treatment of Sensory Impairment
Sensory impairment is a potential early physiological marker for frailty making it an important factor for clinicians and geriatricians managing this multifaceted syndrome (Tan et al., 2020). Future investigations are needed to determine if interventions to optimize vision and hearing in older adults may have the potential to delay or prevent the dysregulation process central to frailty and improve resilience in the face of stressors that might otherwise lead to physical decline and frailty. Such interventions should be part of a multi-pronged frailty intervention including enhancing nutrition and physical activity that have been proposed for older adults. Future work is also needed to establish the cumulative risk of frailty in individuals with dual sensory impairment, i.e. co-occurring vision and hearing impairment.
Clinicians and policymakers should consider adding sensory screening measures to frailty detection programs. In addition, it is important to keep in mind that sensory impairment may also impact how older adults interact with the healthcare system, for example, poorer communication may be an issue that could further impede patient-provider communication and treatment of frail older adults.