Table 3.

Summary of GEE models results for the relationship between outcomes of interests (healthcare costs and HRQoL) and other covariates.

	Healthcare costs‡		HRQoL§
			HUI:2		EQ5D-US
Covariates†	Model 1¶	Model 2¶	Model 1¶	Model 2¶	Model 1¶	Model 2¶
Patients characteristics
Age at baseline	−0.002	0.001	0.003**	0.004*	0.003***	0.004**
Sex (female=0)	−0.040	−0.092	−0.005	0.003	0.022	0.023
Education (≤12 years =0)
>12 years	0.048	0.040	0.011	0.013	0.019	0.021
Marital status (currently married=0)
Not currently married	−0.057	−0.069	−0.043*	−0.038	0.008	−0.002
Clinical measurement
Total NPI score	0.004	0.002	−0.002***	−0.002	−0.002**	−0.002**
CIRS	0.031**	0.030**	−0.004	−0.003	−0.007**	−0.007**
Summated dependence scale	0.173***	0.172***	−0.050***	−0.050***	−0.058***	−0.060***
Parkinson’s disease rating scale	0.006	0.007	−0.007***	−0.007***	−0.008***	−0.008***
Caregiver characteristic
Age at baseline		−0.004		−0.001		−0.001
Sex (female=0)		−0.064		0.014		0.015
Relationship to patients (spouse=0)
Non-spouse		−0.108		−0.016		−0.006
Caregiver subjective burden		0.00004		0.00002		0.002
Caregiver NPI distress score		0.005		−0.002		0.00001

^*P < 0.05;

^**P < 0.01;

^***P < 0.001.

^†CDR, CDR-SB, MMSE, HUI:2 and EQ5D-US were removed from the models due to collinearity with dependence scale (r = 0.77, 0.81, −0.70, −0.78, and −0.78, respectively); Age at onset was removed from the model due to collinearity with age at baseline (r = 0.93); We kept NPI in the GEE models because an independent association between NPI scores and pharmacoeconomic outcomes, over and above dependence scale scores, was found in our previous study.²³

Numbers presented in Table are coefficients from GEE models.

^‡GEE models with Gamma distribution and log link. The estimate of costs of healthcare was applied by y=exp(xβ).

^§GEE models with Gaussian distribution and identity link. The estimate of HRQoL was applied by y=xβ.

^¶The difference between Model 1 and Model 2 was whether caregiver characteristics were included in the model or not.

Abbreviation: HQRoL, health-related quality of life; GEE, generalized estimating equation; MMSE, Mini–Mental State Examination; CDR, Clinical Dementia Rating; CDR-SB, Clinical Dementia Rating sum of boxes scoring; NPI, Neuropsychiatric Inventory; CIRS, Cumulative Illness Rating Scale; HUI:2, Health Utilities Index Mark 2; EQ5D-US, EuroQoL 5 Dimensions with US population scoring.