London School of Hygiene & Tropical Medicine

The findings, published in Alzheimer's & Dementia, suggest a need for greater awareness of the different symptoms of Alzheimer's disease, the most common cause of dementia. The study of 7,815 people - one of the largest of its kind to date - was led by UCL in collaboration with the London School of Hygiene & Tropical Medicine and researchers in the US and Netherlands.

Alzheimer's disease, which currently affects half a million people in the UK, causes the death of brain cells and leads to a range of symptoms, including problems with thinking and memory and changes in behaviour. While memory loss is a typical early symptom of Alzheimer's disease, some people can experience other, very different symptoms in the early stages of the disease. The researchers set out to investigate how a person's age might affect the first symptoms they experience, looking at both cognitive symptoms (problems with thinking skills) and behavioural symptoms.

The team analysed data from 7,815 people in the US National Alzheimer Coordinating Center (NACC) database, which includes records on people attending Alzheimer's disease centres across the US. Each participant had a diagnosis of Alzheimer's, and a record had been made of the symptoms they had first noticed in the early stages of the disease. The average age of the group was 75, with the youngest person aged 36 and the oldest aged 110.

Although memory loss was the most common first symptom in all age groups, the results showed younger people were more likely than their older counterparts to report 'non-memory' problems first - including difficulty with judgement or problem-solving, problems with language, or a loss of visual or spatial awareness. In people under 60, a quarter reported that their first symptom was not memory loss, while one in five people in their 60s first had symptoms other than memory loss. This number fell to one in ten for people in their 70s, and one in 15 for those 80 years or older.

When the researchers compared the people's first reported behavioural symptoms, they also found age differences. The most common behavioural symptom was apathy or withdrawal, but compared to older age groups, younger people were more likely to experience depression or other behavioural symptoms such as anxiety. In contrast, older people were more likely to have had psychosis, or no behavioural symptom at all, compared to those who were younger.

Professor Chris Frost, statistician on the study, said: "Our results highlight the fact that the time course of Alzheimer's disease varies considerably between people. In particular, although memory problems are the most commonly reported first symptom at all ages, the chances of having a non-memory first symptom are greater in those presenting with the disease at younger ages."

The researchers say an awareness of symptoms other than memory loss is vital for helping to diagnose Alzheimer's, particularly for those people whose early symptoms are not typical of the disease. The findings suggest a need for doctors to use tests that do not solely or disproportionately focus on memory, but which also take into account some of the different ways that Alzheimer's can manifest.

The study was part-funded by Alzheimer's Research UK.

Publication

Josephine Barnes, Brad Dickerson, Chris Frost, Lize C Jiskoot, David Wolk, Wiesje M van der Flier. Alzheimer's disease first symptoms are age dependent: evidence from the NACC dataset. Alzheimer's & Dementia. DOI: 10.1016/j.jalz.2014.12.007