Rate of Cognitive Decline Before and After the Onset of Functional Limitations in Older Persons.
BACKGROUND
Loss in physical function is indicative of deterioration in physiological health that may also be associated with deterioration in neurological health. The objective of this study was to examine whether the onset of functional limitations and their severity is associated with increases in cognitive decline among older adults.


METHODS
The study sample consists of 3825 (65% African Americans and 53% females) participants over the age of 65 with no functional limitations. Cognitive function was assessed using a standardized global cognitive score, and functional limitations using a summary measure of 8 Rosow-Breslau and Nagi limitations (ROS-B/Nagi). Cognitive decline before and after the onset of limitations were analyzed using a linear piecewise change point model.


RESULTS
During follow-up, 2682 (70%) participants reported limitations in ROS-B/Nagi measure. The rate of cognitive decline was 0.053-units per year before any limitations, and increased to 0.069-units per year after one or more limitations in ROS-B/Nagi measure. This was about 30% (95% Confidence Interval [CI]: 18 - 42%) increase in the rate of cognitive decline comparing before and after the onset of limitations in ROS-B/Nagi measure. Also, higher number of limitations in ROS-B/Nagi measure at the time of onset was associated with faster cognitive decline.


CONCLUSIONS
The rate of cognitive decline was significantly higher following functional limitations. This study suggests that self-reported measures of functional limitations may serve as an important marker of cognitive decline.
Rush Institute for Healthy Aging, Department of Internal Medicine, Rush University Medical Center, Chicago IL kumar_rajan@rush.edu.
Kumar B
KB
Rajan
Rush Institute for Healthy Aging, Department of Internal Medicine, Rush University Medical Center, Chicago IL.
Liesi E
LE
Hebert
Rush Institute for Healthy Aging, Department of Internal Medicine, Rush University Medical Center, Chicago IL.
Paul A
PA
Scherr
Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor MI.
Carlos F
CF
Mendes de Leon
Rush Institute for Healthy Aging, Department of Internal Medicine, Rush University Medical Center, Chicago IL.
Denis A
DA
Evans
D000203:Activities of Daily Living; D000368:Aged; D002641:Chicago / Q000453:epidemiology; D003072:Cognition Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008137:Longitudinal Studies; D008297:Male; D051346:Mobility Limitation
Cognitive decline; Cognitive function; Cohort studies; Functional limitations; Neurodegeneration