Change in motor function and adverse health outcomes in older African-Americans
Introduction
Late-life motor impairment is a common concomitant of aging and increasingly recognized as a barrier to the maintenance of independence and well-being in old age (Guralnik et al., 1995, Hardy and Gill, 2005, Feinglass et al., 2009). Many studies have shown that the level of motor function is associated with adverse health outcomes including the risk of death (Shipley et al., 2007, Taylor et al., 2009), incident disability (Guralnik et al., 1995), cognitive decline and risk of Alzheimer's disease (Albers et al., 2015). However, loss of motor function, such as reduced strength or slowed walking, is progressive in many older adults (Proctor et al., 2006, Hirsch et al., 2012).
Nonetheless, there are few studies which have employed repeated objective motor performances in older African-Americans to determine if the rate of change in motor function increases with age or have examined the extent to which the rate of progressive motor decline contributes to survival or incident disability in this population. Such data are crucial for efforts to decrease the personal and societal burden of late-life motor impairment in older African-Americans and for efforts to eliminate health disparities.
We used clinical data collected from more than 500 community-dwelling older African-Americans participating in the Minority Aging Research Study (MARS) (Barnes et al., 2012a). Subjects underwent structured testing at baseline and at annual follow-up for up to 10 years. A global motor score was employed to summarize 11 motor performances as previously described (Buchman et al., 2011).
We examined its annual rate of change via a series of linear mixed-effect models which included terms for age, sex, and education and their interaction with the rate of change of global motor scores. Next, we examined whether baseline health status or frequency of physical activities might affect the rate of change in motor function. In further analyses, we examined a proportional hazard model which included separate terms for baseline level and the rate of change in global motor scores to determine whether they are independently associated with the risk of adverse health outcomes. Finally, we calculated the contribution of the rate of change in global motor scores to risk of death and incident disability.
Section snippets
Participants
Participants included self-identified African-Americans from an epidemiologic cohort study of risk factors for cognitive decline called the Minority Aging Research Study (MARS) (Barnes et al., 2012a). The cohort consists of non-institutionalized seniors over the age of 65 who agreed to annual clinical evaluations and cognitive testing. The cohort was recruited from various community-based organizations, churches, and senior subsidized housing facilities in and around the Chicago metropolitan
Descriptive properties of global motor score
There were 513 participants included in these analyses. Their age at baseline ranged from 58 to 94 with an average age of 73.4 (SD = 6.12 years) with interquartile range of 7.58 years. Additional clinical characteristics of these participants at baseline are in Table 1.
Baseline global motor scores ranged from 0.57 to 1.33 with higher values indicating better function. Global motor scores were approximately normally distributed (mean, 1.00; SD, 0.16). Global motor score was associated with age (Rho = −
Discussion
In a cohort of more than 500 older community-dwelling African-American adults, repeated annual objective measures of several motor performances showed that declining motor function accelerates with increasing age. This association was not attenuated when we adjusted for the severity of concomitant health conditions, physical activity or body composition at baseline. Both the level and rate of change in motor function were independently associated with survival and subsequent development of
Acknowledgment
This work was supported by National Institute of Health grants [R01AG22018 (LLB); P30AG10161 (DAB); R01NS78009 (ASB)]; and the Illinois Department of Public Health. We thank all the participants in MARS and Rush Clinical Core. We also thank staffs employed at the Rush Alzheimer's Disease Center.
References (50)
- et al.
At the interface of sensory and motor dysfunctions and Alzheimer's disease
Alzheimers Dement.
(2015) - et al.
Patterns of muscle strength loss with age in the general population and patients with a chronic inflammatory state
Ageing Res. Rev.
(2010) - et al.
Normal walking speed: a descriptive meta-analysis
Physiotherapy
(2011) - et al.
Relationship between test methodology and mean velocity in timed walk tests: a review
Arch. Phys. Med. Rehabil.
(2008) - et al.
Age-related site-specific muscle wasting of upper and lower extremities and trunk in Japanese men and women
Age (Dordr.)
(2014) - et al.
Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in acute stroke treatment
Stroke
(1993) - et al.
Lean mass, muscle strength, and physical function in a diverse population of men: a population-based cross-sectional study
BMC Public Health
(2010) - et al.
Racial differences in the association of education with physical and cognitive function in older blacks and whites
J. Gerontol. B Psychol. Sci. Soc. Sci.
(2011) - et al.
The minority aging research study: ongoing efforts to obtain brain donation in African Americans without dementia
Curr. Alzheimer Res.
(2012) - et al.
Perceived discrimination and cognition in older African Americans
J. Int. Neuropsychol. Soc.
(2012)