Abstract
Childhood aggression has numerous adverse outcomes linked to later cognitive decline, and some of these outcomes, including neurological deficits, are unique to females. Although childhood aggression is uncommon in females, dementia is more prevalent, prompting this study to assess if childhood aggression predicts later cognitive decline in females using data from the Louisville Twin Study (LTS), a sample of identical and fraternal twins and their families. Aggression was measured for 360 twins between the ages of six and eight using the School Behavior Checklist (SBCL); 106 returned for a midlife study (n=106; 38 twin pairs; 30 without pairs). Linear regression suggested that childhood aggression significantly predicted midlife IQ in females, controlling for participants’ last WISC score in childhood ( = −4.31, p = .003). The overall model was significant (R² = .67, F(4, 94) = 48.04, p < .001), and the effect of childhood aggression on midlife IQ was moderated by sex ( = 4.06, p = .042), suggesting the negative association between aggression and midlife IQ was stronger in females than males. A linear mixed model with a random intercept was used to examine between- and within-pair differences in aggression as a predictor of midlife IQ, controlling for WISC scores and sex. Within-pair differences in aggression significantly predicted midlife IQ ( = −7.55, p = .011), and between-pair differences were not significant, indicating that the twin with higher childhood aggression tended to have lower midlife IQ. This effect did not differ significantly by sex (p = .108), though the interaction trended toward a stronger effect in females. We conclude that childhood aggression is a significant predictor of cognitive decline in females, and female twins with higher levels of childhood aggression tend to have lower midlife IQ than their less aggressive cotwin.
