From the Telegraph:
Scientists followed 3,200 over 75s, who had no signs of dementia when they enrolled on the study, for three years. Of those, 217 went on to develop dementia.
They found those who drank between two and three units a day (20 to 30ml) were 29 per cent less likely to have started developing dementia by the end of the three-year period than those who were teetotal.
Two to three units is equivalent to a medium-sized (175ml) glass of wine (2.3 units) or a pint of beer (2.8 units).
The results for Alzheimer's, which accounts for two-thirds of dementia cases, were even more striking: such drinkers were 42 per cent less likely to have developed the disease.
The academics, led by Siegfried Wayerer of the Central Institute of Mental Health in Mannheim in Germany, concluded that "light-to-moderate" alcohol consumption could have a "protective effect" against dementia.
Just one more reason to have a drink with dinner, and wine may be your best bet:
"It is still an open question whether different alcoholic beverages, such as beer, wine and spirits, have a similar effect," they noted.
"Some studies have shown a positive effect of wine only, which may be due either to the level of ethanol [alcohol], the complex mixture that comprises wine or to healthier life-style ascribed to wine drinkers."