Health Outcomes Associated with Self-Reported Vision Impairment in Older Adults.

Visual impairments (that is, blindness or low vision) in late life are closely related to health and have been associated with a range of health-related outcomes that influence and reflect the well-being of older adults (National Academies of Sciences, Engineering, and Medicine, 2016). Independent studies have associated vision impairment with reduced functional capacity and physical activity levels (Crews & Campbell, 2004), reduced psychosocial well-being (Chia, Mitchell, Rochtchina, Foran, & Wang, 2003), morbidity (Crews & Campbell, 2004) and comorbidity (Crews, Jones, & Kim, 2006), self-rated health (Wang, Mitchell, & Smith, 2000), and even mortality (McCarty, Nanjan, & Taylor, 2001). Researchers have also reported relationships between vision impairment and various health risk factors such as obesity (Capella-McDonnall, 2007), inflammation (Seddon, Gensler, Milton, Klein, & Rifai, 2004), and high cholesterol levels (Curcio, Millican, Bailey, & Kruth, 2001). In addition, negative consequences of vision impairment have been studied with respect to secondary health outcomes such as hospital and emergency room utilization (Jacobs, Hammerman-Rozenberg, Maaravi, Cohen, & Stessman, 2005), falls (Crews, Chou, Stevens, & Saaddine, 2016), and hip fractures (Felson et al., 1989). Thus, associations between vision impairment and sundry health outcomes are common, and seem to reflect the relevance of vision as an indicator of the general health status of adults as they age. As part of their Vision Health Initiative, the Centers for Disease Control and Prevention (CDC) have identified as an objective the description and characterization of the public health significance of vision loss and the relationship between vision loss and quality of life, health disparities, and comorbid conditions (CDC, 2016). In the spirit of that goal, the aim of this paper is to describe a nationally representative study that assessed how health outcomes differ by self-reported vision status. The disability process One potential framework for describing how vision impairment is associated with health is the disability process framework, originally proposed by Nagi (1965) and later reconceptualized by Verbrugge and Jette (1994). The framework consists of four stages that progress from (1) risk factors, through (2) pathology to result in (3) reduced functioning, and eventually (4) disability (see Figure 1). RISK FACTORS In developing Nagi's (1965) model, Verbrugge and Jette (1994) defined risk factors as characteristics of an individual (including biological characteristics) that can affect the presence and severity of pathology and impairment. Biological indicators include cholesterol levels, body mass index (BMI), markers of inflammation (such as C-reactive protein, CRP), and indicators of insulin regulation (such as glycated hemoglobin). Accordingly, these biological factors often precede diseases and conditions that lead to functional impairment (including visual impairment), disability, and mortality. For example, glycated hemoglobin--a measure of the average amount of hemoglobin bound to glucose over a prolonged period--could serve as a preclinical indicator of diabetes, and a precursor to diabetic retinopathy, one of the most common causes of vision loss. Several biomarkers have been associated with higher rates of mortality (Harris et al., 1999), reduced cognitive (Wilson, Finch, & Cohen, 2002) and physical (Cohen, Harris, & Pieper, 2003) functioning, and heart disease (Cesari et al., 2003), and are generally viewed as good indicators of the health status of older people (Crimmins et al., 2005), without regard to vision status. In a study that directly compared biological risks of older persons with clinically measured blindness and low vision with older adults with typical vision, Steinman and Vasunilashorn (2011) compared at-risk levels for nine biological markers with underlying relevance in predicting clinical manifestation of conditions commonly experienced by older adults and associated with poorer physiological functioning. …