For example, several studies have shown that APOE ε4 allele may magnify the risk of dementia and cognitive impairment associated with midlife psychosocial factors such as physical inactivity and cognitive inactivity, such that people with these factors are more vulnerable to dementia and cognitive decline when carrying the ε4 allele (Andel et al., 2008; Carlson et al., 2008; Kivipelto et al., 2008). This evidence concerns the gene APOE and dementia.