The recent drop in the number of people developing dementia

It has recently become clear that in the UK dementia has fallen by a fifth over the past 20 years. This is possibly down to lifestyle and education changes. If so this highlights the potential benefits of preventative action:

http://www.theguardian.com/society/2016/apr/19/drop-in-dementia-rates-suggests-disease-can-be-prevented-researchers-say

However a letter published in the Guardian suggests another possible reason for the reduction:

http://www.theguardian.com/society/2016/apr/21/perhaps-unleaded-petrol-heads-are-less-susceptible-to-dementia

I think most people know what a healthy lifestyle involves and it obviously makes sense to try to live healthily. However it is important to realise that there can be no guarantee that a healthy lifestyle will stop the development of dementia in an individual case. And therefore the fact that some people who live a healthy life still develop dementia should not discourage people from taking the steps that may well improve their chances of avoiding dementia.