Increased physical activity in older adults with higher serum neurofilament light chain levels reduces the rate of cognitive decline
Increased physical activity levels in older adults with high serum levels of neurofilament light chain (NFL) leads to a reduction in the rate of cognitive decline. This was the conclusion of a study by researchers from the Rush Institute for Healthy Aging, Rush University Medical Center, Chicago, US.
Neurofilament light chain is a neuronal cytoplasmic protein expressed in large calibre myelinated axons. Furthermore, in both central nervous system and peripheral nervous system diseases associated with axonal injury or degeneration, the concentration of NFL has been found to increase in both cerebrospinal fluid (CSF) and blood.
In addition, levels of CSF NFL are associated with cognitive impairments in patients with Alzheimer disease and fronto-temporal dementia. As a result, it has been suggested that NFL could be used to predict the development of sporadic Alzheimer’s disease and cognitive decline. One factor which appears to be associated with a reduced cognitive decline is physical activity and in a 2011 meta-analysis, the authors concluded that there was a significant and consistent protection for all levels of physical activity against the occurrence of cognitive decline.
For the present study, the US team wanted to examine whether among individuals with high NFL concentrations, increased physical activity was associated with a slowed rate of cognitive decline over time. They turned to the Chicago Health and Aging Project (CHAP), which is a longitudinal population study of common chronic health problems of older persons and in particular, risk factors for incident Alzheimer’s disease.
Blood samples were taken and the concentration of NFL measured at baseline and during each follow-up appointment and dichotomised as low (< 25.5 pg./ml) or high (> 25 pg./ml). Levels of physical activity were self-reported divided into three groups: little activity, medium and high, in which the latter group reported physical activity levels > 150 minutes/week.
A number of cognitive tests were used to assess global cognitive function. The main outcome measure was the association of baseline activity and NFL concentrations with changes in global cognitive function over time.
Increased physical activity and NFL in relation to cognitive decline
A total of 1158 participants with a mean age of 77.4 years (63% female) were included in the study. The mean level of physical activity per week was 170.78 minutes and the geometric mean NFL concentration was 26.1 pg/ml.
Among those with a high NFL levels, indicating more axonal injury, individuals engaging in medium physical activity (< 150 minutes/week), had a 12% slower rate of global cognitive decline compared to those in the low physical activity group. Similarly, those with increased physical activity (i.e., the high group), had a 36% slower rate of decline in comparison to the low physical activity group.
Interestingly, the the rates of cognitive decline were also higher among those with lower levels of NFL, i.e., with less neural damage. For example, in comparison to the group who undertook little or no physical activity, those who undertook medium physical activity had a 43% slower decline and the high activity group, at 30% slower decline.
The authors concluded that among older adults with high levels of serum NFL, increased physical activity levels were associated with a slower rate of cognitive decline. They added that future studies should examine the relationship between cognitive decline and different forms of exercise such as aerobics and strength training.
Desai P et al. Examination of Neurofilament Light Chain Serum Concentrations, Physical Activity, and Cognitive Decline in Older Adults JAMA Netw Open 2022.