Table 4. Multiplicative and additive interactions between childhood health and childhood SES on dementia risk.

Interaction type	Measure	Estimate (95% CI)	P value
Multiplicative interaction (OR scale)
	Unhealthy childhood (without interaction)	1.27 (0.99 to 1.63)	0.061
	Poor SES (without interaction)	1.42 (1.00 to 2.01)	0.048
	Unhealthy childhood (with interaction)	1.44 (0.51 to 4.09)	0.496
	Poor SES (with interaction)	1.44 (1.00 to 2.09)	0.052
	Interaction term	0.88 (0.30 to 2.57)	0.809
Additive interaction (coefficient scale)
	RERI	−0.06 (−1.59 to 1.47)	0.935
	AP	−0.04 (−0.88 to 0.81)	0.935
	S	0.93 (−0.68 to 2.54)	0.259

AP, attributable proportion; RERI, relative excess risk due to interaction; S, synergy index; SES, socioeconomic status.