Table 2.

Number of drugs and prevalence of potentially inappropriate prescribing by quartiles of continuity of GP care

Quartile	Number of prescriptions				Potentially inappropriate prescribing
Quartile	Mean (SD)	P-value^a	IRR (95% CI)^b	P-value^b	Mean (SD)	P value ^a	IRR (95% CI)^b	P-value^b
Usual Provider of Care Index
Lowest quartile	9.67 (5.31)	—	ref	—	2.50 (2.28)	—	ref	—
Low intermediate quartile	9.47 (5.17)	0.20	0.99 (0.96 to 1.01)	0.33	2.47 (2.18)	1.00	1.00 (0.95 to 1.04)	0.89
High intermediate quartile	8.98 (4.93)	<0.01	0.97 (0.94 to 0.99)	0.01	2.29 (2.17)	<0.01	0.96 (0.92 to 1.01)	0.09
High quartile	8.52 (4.75)	<0.01	0.96 (0.93 to 0.98)	<0.01	2.09 (2.06)	<0.01	0.93 (0.88 to 0.97)	<0.01
Bice–Boxerman Continuity of Care Index
Lowest quartile	9.35 (5.23)	—	ref	—	2.40 (2.23)	—	ref	—
Low intermediate quartile	9.29 (5.08)	0.56	0.98 (0.95 to 1.01)	0.11	2.41 (2.22)	0.71	0.99 (0.94 to 1.04)	0.60
High intermediate quartile	9.47 (5.12)	0.36	0.98 (0.96 to 1.01)	0.13	2.44 (2.19)	0.25	0.98 (0.93 to 1.03)	0.41
High quartile	8.56 (4.77)	<0.01	0.96 (0.93 to 0.99)	<0.01	2.09 (2.06)	<0.01	0.93 (0.88 to 0.97)	<0.01
Sequential Continuity Index
Lowest quartile	9.10 (5.10)	—	ref	—	2.30 (2.20)	—	ref	—
Low intermediate quartile	9.70 (5.15)	<0.01	0.98 (0.95 to 1.00)	0.11	2.56 (2.22)	<0.01	0.99 (0.95 to 1.04)	0.80
High intermediate quartile	9.36 (5.22)	0.12	0.98 (0.96 to 1.01)	0.15	2.41 (2.20)	0.04	0.98 (0.93 to 1.02)	0.33
High quartile	8.51 (4.71)	<0.01	0.96 (0.93 to 0.98)	<0.01	2.08 (2.07)	<0.01	0.93 (0.89 to 0.98)	<0.01

↵a Two-sided student t-test.
↵b IRRs estimated using negative binomial regression model, stratified by quartile of CGPC and adjusted for age, sex, 14 comorbidities, and frailty status. CGPC = continuity of GP care. CI = confidence interval. IRR = incidence rate ratio. ref = reference. SD = standard deviation.