If we think about the recent incidents in Llandudno (2 people run over in St Georges Place, Shopfront in Upper Mostyn St demolished), they were both older drivers, to be fair.
I suspect Llandudno's stats are skewed, given the elderly demographic of the area. Nationally, statistics by age are difficult to get hold of, since we rarely know who was to blame. However, we know that in 2011 there were 10,974 accidents involving drivers over the age of 70 compared with 35,953 accidents involving drivers aged 17 - 24.
Even that statistic isn't comparable, since there are probably many more drivers aged above 70 - apparently more than 4.000.000 - than the 17 - 24 year-old age groups. Research by the RAC Foundation suggests drivers aged 75 and over make up 6% of all licence holders but account for just 4.3% of all deaths and serious injuries. By contrast, drivers aged 16-20 make up just 2.5% of all drivers but 13% of those killed and seriously injured.
So yes; the young male driver appears the most dangerous by a long way, but I suspect that many people aged above, say - 75 - might find it increasingly difficult to make quick decisions, such as entering motorways on a slip road (having said that, my impression is that few drivers seem to know how to perform that manoeuvre properly around here...) or dealing with increasingly complex junctions. There's a great example of one of these on the roundabout where the A45 Coventry Road joins the M42 going North. Clearly designed by Satan, or a close relative, this roundabout tests the mettle of even experienced and hardened drivers, so I would feel for anyone with impending dementia.
The important factor in all this, however, is that all individuals are different. Whilst some 70+ drivers might not be safe driving a supermarket trolley, others might well have a background in Police or Army driving and could be far more competent than most younger drivers.