From: Environmental risk factors for dementia: a systematic review
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. |