In the long, slow slide to oblivion called ageing, men go first, according to research. They are more likely than women to lose their memory and have difficulty thinking.
A study of older people in their 70s and 80s has revealed that mild cognitive impairment marked by symptoms such as increasing forgetfulness was 50 per cent higher in men than in women.
Mild cognitive impairment (MCI) involves a level of mental decline beyond that which can be explained by normal ageing. It is often associated with dementia and Alzheimer's disease later in life.
The onset of dementia is a slow process of mental derangement that strips sufferers of their memory, personality and, eventually, their humanity. It is a progressive, neuro-degenerative disorder that is incurable and irreversible. Some people subside gently into dementia without evident distress, but for others the experience of losing their mental faculties is confusing, distressing and – in some cases – frightening. In the case of Alzheimer's, the condition is thought to be caused by the build-up of protein deposits in the brain – called "plaques and tangles" – whose first symptoms may be a difficulty in finding words.
Scientists from the Mayo Clinic in Rochester, Minnesota, one of the premier research institutes in the US, tested the memory and thinking skills of more than 2,000 people aged 70 to 89.
They found that more than one in six (16 per cent) had mild cognitive impairment, one in 10 was suffering from dementia, and three-quarters had normal mental faculties. A total of 19 per cent of men were affected with MCI, compared with 14 per cent of women.
Lead researcher Dr Ronald Petersen said: "This is the first study conducted... to find a higher prevalence of MCI in men. The finding that the frequency of mild cognitive impairment is greater in men was unexpected, since the frequency of Alzheimer's disease is actually greater in women. It warrants further study.
"If these results are confirmed in other studies, it may suggest that factors related to gender play a role in the disease. For example, men may experience cognitive decline earlier in life but more gradually, whereas women may transition from normal memory directly to dementia at a later age but more quickly."
When combined, the figures suggest 25 per cent of the population aged 70 and over have dementia or are at risk of developing it in the near future.
"With the [increase in ageing], these numbers are staggering and the impact on the healthcare economy, as well as on individuals and their families, is quite impressive. The need for early diagnosis and therapeutic intervention is increasingly important," Dr Peterson said.
The study is published in the journal Neurology.