Most people's mental faculties tend to decline as they get older but it can be hard to disentangle what are the normal side effects of the ageing process - Mild Cognitive Impairment (MCI) - from the beginnings of dementia. A study of 105 people with MCI in Poland tested people yearly. The researchers found that after 3 years 23 of the original sample had developed dementia, 40 got worse but as a normal part of the ageing process, 34 were stable and 8 actually improved. Those people with depression were more likely to go on to develop full-blown dementia as were those who had cognitive problems as well as memory problems. A higher level of a substance called homocysteine in the bloodstream was also associated with an increased risk of going on to develop dementia.
Gabryelewicz, T. ... [et al] - The rate of conversion of mild cognitive impairment to dementia : predictive role of depression International Journal of Geriatric Psychiatry June 2007, 22(6), 563-567