Identifying risk factors of young-onset dementia and evaluating evidence hierarchy: a meta-analysis and umbrella review.

Highly suggestive associations (Class II Evidence) were defined by highly significant summary estimates ( p -value under random-effects models<1 × 10 –6 ), more than 1000 YOD cases, and a p -value<0.05 in the largest study.

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While the reported associations may be significant, they do not directly imply causality.

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