A Blood Biomarker Linked to Mortality in Older Adults
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Understanding Biological Age
Mirrors may provide a better estimate of your biological age than your calendar. While chronological and biological ages generally align, some individuals may age at a different pace than what their birth date suggests. A significant challenge in aging research is identifying biological markers that reflect individual aging rates accurately.
The search for reliable aging indicators continues. Although epigenetic clocks have gained popularity, they require further refinement. It seems we may need to integrate multiple clocks and biomarkers to accurately gauge biological age, surpassing what a mirror can reveal. The question remains: which biomarkers should we focus on?
Ideally, we would utilize markers that can be easily monitored through regular blood tests. Many blood protein levels fluctuate over time, correlating with biological aging processes, although these measures are not infallible. Alternatively, we could examine specific cellular debris present in our bloodstream.
Exploring Neurofilament Light Chain
Recent research has highlighted an intriguing potential marker: blood levels of neurofilament light chain (NfL), which strongly correlate with cerebrospinal fluid levels. NfL is a structural protein found in nerve cells, and elevated blood levels may indicate nerve damage, even in the absence of obvious symptoms. High NfL levels have been associated with cognitive decline and lower survival rates in Alzheimer’s patients.
The researchers aimed to investigate whether NfL levels could also provide insights into late-life mortality more broadly.
Study One: Centenarians
In a study involving 135 centenarians monitored over four years, individual variability in NfL levels was notable. Increases in NfL levels were linked to mortality more effectively than any other measures, particularly when combined with the activity of daily living (ADL) score.
Study Two: Nonagenarians
A second cohort of 180 nonagenarians exhibited a similar trend. After adjusting for ADL and the Mini-Mental State Examination (MMSE), each standard deviation increase in NfL corresponded to a 22% increase in mortality risk.
Study Three: Mice Research
In a study involving mice, researchers observed comparable results. Higher NfL levels and greater variability with age were noted. Interestingly, in a specific strain of mice known to benefit from calorie restriction, reducing calorie intake during middle age led to a significant decrease in NfL levels—by nearly half. However, these reductions were less pronounced in older mice.
Caveats and Implications
It's important to note that findings for individuals aged 90 and above may not apply to younger populations. Other markers might be more closely related to biological age in younger groups. NfL may show a strong correlation primarily in otherwise healthy individuals reaching their ninth decade or in younger individuals with certain neurodegenerative conditions. Different life stages might require distinct biomarkers.
Additionally, not all participants completed the necessary assessments and blood tests, which could introduce bias, as those who did may be healthier. The study's participants were all Danish, which could further influence the results.
As a singular marker, NfL may not provide a comprehensive view. The authors summarize their findings as follows:
In conclusion, our observations suggest that deterioration in nervous system function contributes to late-life mortality, making blood NfL a potentially valuable biomarker for predicting all-cause mortality.
For reference, a rough target for NfL levels is below 40 pg/ml.
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