Building the evidence for an ecological model of cognitive health.

This is a commentary on Besser and colleagues' article "Associations between neighbourhood built environment and cognition vary by apolipoprotein E genotype: Multi-Ethnic Study on Atherosclerosis" published in Health & Place. Unlike previous studies, the authors found significant environment-cognition associations in apolipoprotein E (APOE) ε2 carriers and no significant associations in ε4 carriers. This commentary discusses the possible reasons for these findings and, in doing so, proposes an ecological model of cognitive health. The model highlights the importance of accounting for multiple environmental influences including the built and natural environment and air and noise pollution indicators. It also stresses the importance of studying the underlying biological mechanisms explaining differences in environment-cognition associations across APOE genotype categories.