What is cognitive function, and how does it develop?
Cognitive function refers to the set of mental processes involved in acquiring, processing, storing, and retrieving information. Normal cognitive aging is characterized by:
- A gradual reduction in processing speed (–10 to 20% between the ages of 30 and 70).
- A slight reduction in working memory (the ability to hold information in short-term memory).
- Executive functions (planning, flexibility) that begin to decline around ages 60–65.
- Semantic and procedural memory remain relatively intact into old age.
This normal aging process should be distinguished from MCI (Mild Cognitive Impairment) and dementias, which require a medical diagnosis. Nutritional factors can influence the rate of normal cognitive aging but do not treat neurodegenerative diseases.
Do omega-3s help preserve cognitive function as we age?
Omega-3 DHA fatty acids are the structural fatty acids of neuronal membranes, and their levels decline with age. Their roles include:
- Maintaining neuronal membrane fluidity: essential for the speed of synaptic transmission.
- Production of BDNF: DHA stimulates the expression of BDNF, a growth factor that supports neuroplasticity and hippocampal neurogenesis.
- Reducing neuroinflammation: a central mechanism of accelerated cognitive aging.
Prospective epidemiological studies (MAPT, FINGER) link high DHA intake to better preservation of cognitive function in people over 65.
Do vitamin B12 and vitamin D3 protect cognitive function?
Two vitamins have been extensively studied:
- Vitamin B12: Deficiency builds up silently over the course of years. People over 60 with homocysteine levels > 11 µmol/L have a threefold higher risk of cognitive decline in longitudinal studies.
- Vitamin D3: Insufficiency (< 20 ng/mL) is associated with a 1.5- to 2-fold increased risk of dementia in several cohorts. It modulates NGF expression and reduces microglial neuroinflammation.
Do CoQ10 and resveratrol slow cognitive decline?
Two antioxidant compounds have been studied in relation to cognitive aging:
- Coenzyme Q10 (ubiquinol): its synthesis decreases by 50% between the ages of 20 and 80. Supplementation (100 to 300 mg/day) may improve mitochondrial bioenergetics in neurons and tolerance to cognitive fatigue. Its combination with omega-3s is synergistic.
- Resveratrol: activates SIRT1 (a regulator of cellular aging) and improves cerebral blood flow. Studies show improved working memory scores after 6 months of supplementation.
How does deep sleep preserve cognitive function?
Deep sleep is an irreplaceable brain-cleaning mechanism:
- Glymphatic system: perivascular spaces expand by 60% during deep sleep, eliminating beta-amyloid and tau protein implicated in Alzheimer’s disease.
- Memory consolidation: episodic memory is transferred to long-term memory primarily during deep non-REM sleep and REM sleep.
- Restoration of neurotransmitter reserves: serotonin, dopamine, and norepinephrine are replenished during sleep.
Longitudinal studies show that sleeping less than 6 hours per night over a 10-year period is associated with a significantly higher risk of dementia.
What habits best preserve cognitive function?
Beyond supplements, lifestyle habits have a greater impact:
- Regular physical activity (150 min/week of aerobic exercise): the only intervention with a proven neuroprotective effect in randomized trials. It increases BDNF and stimulates hippocampal neurogenesis.
- Lifelong learning: strengthens cognitive reserves, which delay the clinical onset of neurodegenerative diseases.
- An active social life: Social isolation is as strong a risk factor for dementia as hypertension, according to the 2020 Lancet Commission report.
- Chronic stress management: Chronically elevated cortisol reduces hippocampal neurogenesis and progressively impairs episodic memory.
