Table 3.

Evaluation of additive and multiplicative interaction between severity of sidewalk problems and activity limitations on the likelihood of going into the neighborhood less than one time per week compared to the likelihood of going into the neighborhood one to seven times per week.

		Activity Limitations				ORs (95% CI) for activity limitations within strata of sidewalk problemsb	Measure of interaction on additive scale: RERI (95% CI)c	Measure of interaction on multiplicative scale: Ratio of ORs (95% CI)d
		None		Any
		N Y=1/Y=0a	OR (95% CI)	N Y=1/Y=0a	OR (95% CI)
Severity of Sidewalk Problems	Not really a problem	597/4490	1.00	180/386	2.63 (2.13, 3.24); P<0.01	2.52 (2.03, 3.13); P<0.01
	Minor problem	272/1801	1.17 (1.00, 1.37); P=0.05	91/199	2.82 (2.14, 3.72); P<0.01	2.40 (1.77, 3.27); P<0.01	0.02 (-0.87, 0.91); P=0.48	0.91 (0.64, 1.30); P=0.62
	Somewhat serious problem	138/668	1.49 (1.21, 1.83); P<0.01	52/101	3.07 (2.14, 4.40); P<0.01	2.12 (1.39, 3.23); P<0.01	−0.04 (−1.41, 1.32); P=0.53	0.79 (0.51, 1.22); P=0.29
	Very serious problem	161/600	1.71 (1.40, 2.09); P<0.01	52/75	3.67 (2.51, 5.36); P<0.01	2.32 (1.51, 3.55); P<0.01	0.33 (−1.13, 1.79); P=0.33	0.81 (0.52, 1.28); P=0.38
ORs (95% CI) for minor sidewalk problems within strata of activity limitationse			1.18 (1.01, 1.38); P=0.04		1.05 (0.77, 1.43); P=0.78
ORs (95% CI) for somewhat serious sidewalk problems within strata of activity limitationse			1.49 (1.21, 1.84); P<0.01		1.11 (0.75, 1.64); P=0.61
ORs (95% CI) for very serious sidewalk problems within strata of activity limitationse			1.72 (1.41, 2.10); P<0.01		1.36 (0.91, 2.04); P=0.14

Note: OR = Odds Ratio; CI = Confidence Interval; RERI = Relative Excess Risk due to Interaction; All odds ratios presented in this table are adjusted for age, race, gender, individual income, individual education, mobility aid use (Model 6); Table presentation is following the recommendations from Knol and VanderWeele (2012).

^aY=1 represents the number of participants reporting going into the neighborhood less than one time per week, Y=0 represents the number of participants reporting going into the neighborhood one to seven times per week

^bOdds ratios obtained from separate, stratified models among participants reporting severity of sidewalk problems as: not really a problem (N= 5,653), minor problem (N=2,363), somewhat serious problem (N=959), very serious problem (N=888). Adjusted odds ratios of the relationship between activity limitations and going into the neighborhood less than one time per week compared to one to seven times per week reported above.

^cRelative Excess Risk due to Interaction (RERI) represents the differences in differences in odds ratios. RERI can be more precisely written as: OR₁₁- (OR₁₀+OR₀₁-1), OR₁₂- (OR₁₀+OR₀₂-1), OR₁₃- (OR₁₀+OR₀₃-1) for minor, somewhat serious, and very serious sidewalk problems, respectively. Where activity limitations = i (0 = no activity limitations, 1 = any activity limitations) and sidewalk problems = j (0 = Not really a problem, 1 = Minor problem, 2 = Somewhat serious problem, 3 = Very serious problem) for all OR_ij.

^dRatio of Odds Ratios can be written as: OR₁₁/(OR₁₀×OR₀₁), OR₁₂/(OR₁₀×OR₀₂), OR₁₃/(OR₁₀×OR₀₃) for minor, somewhat serious, and very serious sidewalk problems, respectively. Where activity limitations = i (0 = no activity limitations, 1 = any activity limitations) and sidewalk problems = j (0 = Not really a problem, 1 = Minor problem, 2 = Somewhat serious problem, 3 = Very serious problem) for all OR_ij.

^eOdds ratio obtained from separate, stratified models among participants reporting the number of activity limitations: none (N= 8,727), any (N= 1,136). Adjusted odds ratios of the relationship between severity of sidewalk problems and going into the neighborhood less than one time per week compared to one to seven times per week reported above.