Difficulty reading faces could be early warning sign of dementia, researchers say

People who see smiles in neutral or negative faces may be showing early dementia signs, with brain scans linking this bias to cognitive decline.

Around 944,000 people in the UK live with dementia, and experts predict the number will pass one million by the end of the decade.

Alzheimer’s is the most common form of the condition, thought to be caused by a build-up of proteins in the brain, including tau and amyloid.

While memory loss is the best-known symptom, difficulty reading facial expressions may also be an early warning.

Past research has found that the ability to recognise emotions in faces declines even with small drops in cognitive function. The steepest fall is in spotting negative feelings such as anger, fear and disgust, while happiness recognition is least affected.

Scientists from the UK and Israel studied 665 people aged 18 to 89, split into roughly 10-year groups.

Participants identified emotions in computer-generated faces while undergoing MRI scans and tests for cognitive decline and depression.

Older participants were far more likely to interpret uncertain or ambiguous faces as happy, while younger groups more readily picked up on negative expressions such as fear or anger.

This “positivity bias” was strongest in those with poorer brain function.

Brain scans showed the bias was linked to reduced grey matter in the hippocampus and amygdala, areas that process memory and emotion.

Dementia damages these regions, which may explain why some people misread faces long before memory loss appears.

The bias was associated with worse performance on thinking and memory tests but not with depression, suggesting it stems from brain changes rather than mood.

“The lack of association with depressive symptoms suggests that positivity bias could help distinguish cognitive decline from depression in old age,” the researchers wrote.

Negative emotions such as anger, fear and sadness were harder to detect than happiness, which may partly explain the results.

But the study only looked at people at a single point in time. It did not track how brain function changed as they aged, so more research is needed to confirm whether positivity bias really predicts dementia.

“Our study supports the idea that age-related positivity reflects neurodegeneration, but this requires confirmation in future longitudinal studies,” the authors said.

Lead scientist Dr Noham Wolpe, from Tel Aviv University, added: “We are exploring how these findings relate to older adults with early cognitive decline, particularly those showing signs of apathy, which is often another early sign of dementia.”