Elsevier

Experimental Gerontology

Volume 70, October 2015, Pages 71-77
Experimental Gerontology

Change in motor function and adverse health outcomes in older African-Americans

https://doi.org/10.1016/j.exger.2015.07.009Get rights and content

Highlights

  • We tested whether declining motor function accelerates in older African-Americans.

  • The rate of motor decline increased an additional 4%/year of age at baseline.

  • Both level and rate of motor decline predicted death and incident disability.

Abstract

Objective

We tested whether declining motor function accelerates with age in older African-Americans.

Methods

Eleven motor performances were assessed annually in 513 older African-Americans.

Results

During follow-up of 5 years, linear mixed-effect models showed that motor function declined by about 0.03 units/year (Estimate, − 0.026, p < 0.001); about 4% more rapidly for each additional year of age at baseline. A proportional hazard model showed that both baseline motor function level and its rate of change were independent predictors of death and incident disability (all p's < 0.001). These models showed that the additional annual amount of motor decline in 85 year old persons at baseline versus 65 year old persons was associated with a 1.5-fold higher rate of death and a 3-fold higher rate of developing Katz disability.

Conclusions

The rate of declining motor function accelerates with increasing age and its rate of decline predicts 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.

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