Physical status as a moderator of depressive symptoms among older adults with dual sensory loss.

A simultaneous deficit in vision and hearing, referred to as dual sensory loss (DSL), is a common occurrence in older age. Population estimates of the percentage of older persons who experience DSL have varied widely (from a low of 7.3% to a high of 21%), based on method used to define hearing and vision loss and the age of the population studied (Brennan, Horowitz, & Su, 2005; Caban, Lee, Gomez-Marin, Zhen, & Lam, 2005; Campbell, Crews, Moriarty, Zack & Blackman, 1999; Crews & Campbell, 2004). Regardless of the current prevalence, DSL is expected to increase in future years as the population ages and the lifespan increases. The occurrence of DSL in older adults is a concern because it is associated with several negative outcomes, including depression and functional disability (e.g., McDonnall, 2009a; Brennan, Horowitz, & Su, 2005; Capella-McDonnall, 2005; Crews & Campbell, 2004; Horowitz & Reinhardt, 1993; Keller, Morton, Thomas, & Potter, 1999; Lupsakko, Mantyjarvi, Kautiainen, & Sulkava, 2002). It has even been suggested that a primary pathway between sensory loss and depression is through functional disability (Horowitz, Reinhardt, Boerner, & Travis, 2003; Horowitz, 2006). Although the association between DSL and depression in older adults has been well documented, ways to moderate that relationship have not been investigated. Many variables could potentially moderate the relationship between depression and DSL, but only some of these variables are capable of being modified by the individual. Focusing on adaptable variables is important because they offer individuals a chance to reduce their experience of depressive symptoms and have the potential to be included in interventions with this population. The purpose of the present study was to evaluate three physical status variables (physical activity, physical condition, and body mass index) as potential moderators of the relationship between DSL and depressive symptoms. In addition to being adaptable, physical status was selected for investigation because of the proposed relationship between functional disability and depression for persons with sensory loss, as decline in physical status has been shown to commonly precede functional disability in the general older population (Fonda & Herzog, 2004; Sarkisian et al., 2000). The many health benefits of regular physical activity are well-known, and persons of all ages, including older adults, are encouraged to participate (U.S. Department of Health and Human Services, 1999). In fact, older adults may have more to gain by being physically active than younger persons, as a physically active lifestyle is considered one of the most important factors contributing to successful aging (Agency for Healthcare Research and Quality [AHRQ], 2002). Physical activity has been shown to enhance strength, aerobic capacity, and physical functioning in older adults, and there is even some evidence to suggest that physical activity slows the development or progression of functional limitations (Keysor, 2003). Despite all this, older adults are less likely to engage in regular physical activity than younger people and very few older adults achieve the minimum recommended amount of activity (AHRQ, 2002). Physical activity is also known to have a positive effect on depression: Persons who participate in a regular program of exercise or physical activity have been shown to experience less depression than those who do not. A significant amount of research has supported this relationship for the general population (e.g., Farmer et al., 1988; De Moor, Beem, Stubbe, Boomsma, & De Geus, 2006; see Mead et al., 2008 for a systematic review of randomized controlled trials in this area) as well as for the population of older adults (e.g., Barbour & Blumenthal, 2005; Blake, 2009; Taylor et al., 2004). With a few exceptions, the experimental research in this area has included only persons with major or minor depression or depressive symptoms, but cross-sectional research has involved all persons regardless of their initial levels of depression. Overweight and obesity are usually associated with a low level of physical activity, and they have increased at an alarming rate in recent years. The current estimate of adults age 60 and older who are overweight or obese is 68.6%, or more than two-thirds of the population (Flegal, Carroll, Ogden, & Curtin, 2010). Overweight and obesity are considered two of the most important public health problems of our time (Simmons-Morton, Obarzanek, & Cutler, 2006) because they are associated with a multitude of medical conditions and negative psychosocial outcomes (CDC, 2009; Ball, Crawford, & Kenardy, 2004; Simon et al., 2006). Obesity (as measured with body mass index [BMI]) has been associated with higher levels of depression (e.g., Bertakis & Azari, 2005; Johnston, Johnson, McLeod, & Johnston, 2004) and has been shown to predict future depression among older adults (Sachs-Ericsson et al., 2007; Strawbridge, Deleger, Roberts & Kaplan, 2002). In addition, fewer symptoms of depression was one of the benefits associated with decreasing BMI (Dixon, Anderson, Cameron-Smith, & O’Brien, 2004). Depression is a significant problem for older persons who experience a DSL. This relationship is well-documented, but research on the ability of adaptable factors to moderate the relationship is lacking. Research involving the general population of older adults has documented an association between physical activity and lower levels of depression and between obesity and higher levels of depression. The purpose of the present study was to evaluate the ability of physical status, measured by physical activity, physical condition, and BMI, to moderate the relationship between DSL and depressive symptoms. It is possible that these variables have a greater association with depressive symptoms for persons with DSL than for persons without sensory loss. One of the common effects of developing a vision loss or DSL in older age is a reduction in activities (McDonnall, 2009a; Rovner & Casten, 2002). This includes physical activity, because barriers such as lack of transportation, lack of accessible exercise equipment or facilities, and reduced opportunities for safe physical activities are commonly associated with the loss of vision and DSL. Therefore, it was hypothesized that these three measures of physical status would moderate the relationship between DSL and depressive symptoms, and provide a benefit larger than that exhibited for persons without sensory loss.