Spinal motor neurons and motor function in older adults
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This study examined the relation between lumbar spinal motor neuron (SMN) indices and motor function proximate to death in community-dwelling older adults. Older adults (N = 145) participating in the Rush Memory and Aging Project underwent structured clinical testing proximate to death and brain and spinal cord autopsy at time of death. Ten motor performances were summarized by a composite global motor score. Choline acetyltransferase immunostaining was used to identify spinal motor neurons of the L4/5 segment. SMN counts and area and ventral horn area were collected. Linear regression modeling showed that the association of SMN counts and density with global motor scores proximate to death varied with sex. Separate models in men and women showed that this significant interaction was due to the association of higher SMN counts and density with higher global motor scores proximate to death in men but not women. These associations were unchanged when we controlled for indices of brain pathologies or chronic health conditions. In 38 cases with counts of activated microglia available, higher counts of activated microglia were associated with lower SMN counts. Activated spinal microglia and loss of spinal motor neurons may contribute to motor impairments in older men.
KeywordsAging Motor function Spinal motor neurons Spinal microglia
Spinal motor neuron
Central nervous system
Peripheral nervous system
TAR DNA-binding protein 43
Body mass index
We thank all the participants in the Rush Memory and Aging Project. We also thank the staff of the Rush Alzheimer’s Disease Center. More information regarding obtaining (MAP) data for research use can be found at the RADC Research Resource Sharing Hub (http://www.radc.rush.edu).
This work was supported by National Institute of Health Grants [R01AG17917 (DAB); R01AG24480; R01NS78009; R01AG43379 (ASB); R01AG47976]; and the Illinois Department of Public Health.
Compliance with ethical standards
Conflicts of interest
The authors do not declare any conflict of interest for this manuscript.
The study was approved by the Institutional Review Board of Rush University Medical Center.
Written informed consent was obtained from all study participants.
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