Aging, Dementia & Brain Longevity
Cognitive Decline FAQ
When decline starts, what separates normal aging from dementia, and what actually protects the aging brain. Take the MoCA test to screen your cognitive health today.
At what age does cognitive decline start?
Processing speed and working memory begin declining around age 25. More complex abilities like vocabulary and crystallised knowledge peak in the 50s. Most people don't notice decline until their 60s-70s, when multiple domains decline together.
What is the difference between normal aging and dementia?
Normal aging produces gradual, mild slowing. Dementia produces functional impairment across multiple domains — memory, language, judgement, and daily living. The key word is impairment: if it interferes with daily life, it is not normal aging.
What is mild cognitive impairment (MCI)?
MCI is the clinical grey zone between normal aging and dementia — measurable cognitive decline beyond what's expected for age, but not severe enough to impair daily functioning. About 15–20% of people over 65 have MCI. Roughly 10–15% per year convert to dementia.
Can cognitive decline be reversed?
Partially, depending on the cause. Decline from vascular risk factors (hypertension, diabetes) can be slowed or partially reversed by treating the underlying condition. Alzheimer's-type decline cannot currently be reversed, but its rate can be slowed by lifestyle factors.
What are the early signs of dementia?
The most common early sign is short-term memory loss — forgetting recent events while remembering the distant past. Other early signs: difficulty finding words, getting lost in familiar places, trouble with complex tasks, personality changes, and poor judgement.
How does the MoCA test detect cognitive decline?
The MoCA screens 8 cognitive domains in ~10 minutes: visuospatial, naming, memory, attention, language, abstraction, delayed recall, and orientation. A score below 26/30 suggests MCI. It detects early Alzheimer's with ~90% sensitivity — far better than the older MMSE.
What lifestyle factors protect against dementia?
The Lancet Commission (2024) identifies 14 modifiable risk factors that together account for ~45% of dementia cases. The most impactful: physical inactivity, untreated hypertension, hearing loss, heavy alcohol use, smoking, social isolation, and poor sleep.
How fast does reaction time decline with age?
Reaction time declines approximately 2–4ms per year after age 25, accelerating after 60. By age 70, the average RT is around 400ms vs 238ms at the peak (age 20–24). This reflects declining myelin sheath integrity and reduced dopaminergic function.
What is vascular dementia?
Vascular dementia is caused by reduced blood flow to the brain — from strokes, small vessel disease, or cardiovascular risk factors. It is the second most common form of dementia after Alzheimer's. Unlike Alzheimer's, it can sometimes be slowed by aggressively treating cardiovascular risk.
Can brain training prevent cognitive decline?
The evidence is mixed. The ACTIVE trial (2832 adults, 10-year follow-up) found that speed-of-processing training reduced dementia risk by 29%. Other forms of brain training show narrower transfer. Aerobic exercise has stronger and more consistent evidence for dementia prevention.
Understanding Cognitive Aging
Cognitive aging is universal — but its rate varies enormously based on genetics, lifestyle, and early-life factors. The science of dementia prevention has advanced dramatically in the last decade, with the Lancet Commission now identifying 14 modifiable risk factors.
This FAQ covers the most searched questions about cognitive decline — from when it starts and how to recognise it, to the MoCA test, vascular dementia, and the evidence for brain training.
Use the MoCA test as a baseline screen, and the Reaction Time test to track your processing speed over time.
Cognitive Changes by Decade
| Age | Processing speed | Working memory | Vocabulary |
|---|---|---|---|
| 20s | Peak | Peak | Growing |
| 30s | −2–3% | −2% | Peak |
| 40s | −5% | −5% | Peak |
| 50s | −10% | −10% | Peak / stable |
| 60s | −20% | −18% | Slight decline |
| 70s+ | −35% | −28% | Moderate decline |
Screen your cognitive health
Take the MoCA-based cognitive assessment — 8 domains, 10 minutes, instant score. No account needed.