Table 1 Definitions of the strength of the reported association between individual risk factors and dementia

Strong evidence for environmental risk factor

 There is a reported association with dementia in the majority of published papers.

Moderate or weak evidence for environmental risk factor

 Although the reported association with dementia is not seen in the majority of published papers, at least one published paper (or only one) supports the association.

 Weak evidence may come from a single, poorly designed study.

No evidence for environmental risk factor

 No association with dementia has been revealed either due to a lack of relevant research or the observed effect is not seen as significant.