Non-linear relationship between age and subfoveal choroidal thickness in Chinese patients with proliferative diabetic retinopathy

Table 4 Non-linearity addressed by a two-piecewise linear regression model

For exposure: Age	SFCT (μm)
Outcome, Model	β	95%CI	P value
Fitting model by standardized linear regression	-1.68	-2.97 to -0.39	0.0117
Fitting model by two-piecewise linear regression
Inflection point of age	54.00
≤ 54	2.00	-0.16 to 4.17	0.0712
> 54	-4.89	-6.87 to -2.90	< 0.0001
Log likelihood ratio test			< 0.0010

The adjustment strategy was the same as the adjusted Model III.