Estimating and Interpreting Effects from Nonlinear Exposure-Response Curves in Occupational Cohorts Using Truncated Power Basis Expansions and Penalized Splines

Table 2

Estimated hazard ratios and 95% pointwise confidence intervals from separate Cox proportional hazard models using the carpal tunnel syndrome and strain index exposure data.

Exposure value; x	Linear	Logarithmic	Linear spline with knot at 13.5	Penalized spline function with
0.8	1.01; (0.99, 1.03)	1.21; (0.92, 1.59)	1.10; (1.01, 1.20)	1.04; (0.97, 1.11)
6.0	1.10; (0.94, 1.29)	1.88; (0.77, 4.62)	2.09; (1.10, 4.00)	1.35; (0.81, 2.27)
9.0	1.15; (0.91, 1.46)	2.11; (0.73, 6.11)	3.03; (1.15, 7.99)	1.57; (0.78, 3.16)
13.5	1.24; (0.86, 1.77)	2.38; (0.69, 8.19)	5.27; (1.23, 22.57)	1.89; (0.78, 4.60)
18.0	1.33; (0.82, 2.14)	2.60; (0.67, 10.13)	4.85; (1.23, 19.04)	2.12; (0.79, 5.75)
20.3	1.38; (0.80, 2.36)	2.70; (0.66, 11.08)	4.65; (1.23, 17.65)	2.18; (0.78, 6.11)
54.0	2.33; (0.55, 9.84)	3.68; (0.58, 23.35)	2.51; (0.44, 14.42)	2.32; (0.38, 14.15)