Table 4.

Mediation of the Association Between Neighborhood Socioeconomic Status Score and Infection

Characteristic	Natural Indirect Effecta		Natural Direct Effectb		Percentage Mediated (Log Hazard Scale)
	HR	(95% CI)c	HR	(95% CI)c
Adjusted (Q4 [highest] vs Q1 [lowest])d	…	…	0.76	(.65–.90)	…
Potential mediators
Weakness (SF-12 PCS <75)	0.94	(.92–.96)	0.81	(.69–.95)	21.5
Individual income	0.96	(.92–.99)	0.80	(.68–.94)	16.5
Diabetes	0.97	(.96–.98)	0.78	(.67–.92)	10.7
Exhaustion	0.98	(.97–.99)	0.78	(.67–.92)	8.5
BMI (obese vs nonobese)	0.98	(.97–1.00)	0.78	(.66–.91)	6.1
Low physical activity	0.99	(.98–1.00)	0.77	(.66–.91)	4.5

Total of 12463 Reasons for Geographic and Racial Differences in Stroke (REGARDS) participants in lowest or highest quartiles of nSES score with complete covariate data. Characteristics added as the only additional covariate relative to the adjusted model.

Abbreviations: BMI, body mass index; CI, confidence interval; HR, hazard ratio; nSES, neighborhood socioeconomic status; PCS, physical composite score; SF-12, 12-Item Short-Form Health Survey.

^aNatural indirect effect represents the component of the exposure effect that is mediated, reported on the hazard ratio scale.

^bNatural direct effect represents the component of the exposure effect not mediated, reported on the hazard ratio scale.

^cConfidence intervals estimated using the delta method.

^dInitial hazard ratio comparing lowest to highest quartile of nSES score (lowest as referent) from Cox proportional hazards model adjusted for age, sex, race, education, geographic region, chronic lung disease, hypertension, stroke, myocardial infarction, smoking, alcohol use, C-reactive protein, and estimated glomerular filtration rate (chronic kidney disease).