Commissions from the Lancet journals:
Dementia prevention, intervention, and care
Published: July 20, 2017
Executive Summary
Dementia is the greatest global challenge for health and social care in the 21st century: around 50 million people worldwide have dementia and this number is predicted to triple by 2050. The Lancet Commission on dementia aims to review the best available evidence and produce recommendations on how to best manage, or even prevent, the dementia epidemic.

Dementia is not an inevitable consequence of ageing and the Commission identifies nine potentially modifiable health and lifestyle factors from different phases of life that, if eliminated, might prevent dementia. Although therapies are currently not available to modify the underlying disease process, the Commission outlines pharmacological and social interventions that are able to help manage the manifestations of dementia.

According to their survey 35% falls in to potentially modifiable Factors

It is neatly presented in their Info-Graphics diagram which can be viewed by registered members.