Table 2.

Factors contributing to non-adherence for all oral drugs.

	Non-adherent (PRR > 0.2) n = 695 (57.6)	Adherent (PRR ≤ 0.2) n = 512 (42.4)	Total n = 1207 (100)	Odds ratio (95% CI)	P value	C-statistic
PATIENT FACTORS
Age, n (%)
<40	48 (6.9)	29 (5.7)	77 (6.4)	1.13 (0.64–2.00)	0.682	0.637
40–59	113 (16.3)	73 (14.3)	186 (15.4)	1.02 (0.66–1.59)	0.913	–
60–74	266 (38.3)	184 (35.9)	450 (37.3)	1.02 (0.74–1.40)	0.919	–
≥75	268 (38.6)	226 (44.1)	494 (40.9)	1.00	NA	–
Sex, n (%)
Male	300 (43.2)	232 (45.3)	532 (44.1)	0.90 (0.71–1.14)	0.395	0.638
Female	395 (56.8)	280 (54.7)	675 (55.9)	1.00	NA	–
Patient copayment, n (%)
0%	89 (12.8)	54 (10.5)	143 (11.8)	1.67 (1.12–2.50)	0.011*	0.637
10%	270 (38.8)	221 (43.2)	491 (40.7)	1.10 (0.85–1.43)	0.452	–
30%	336 (48.3)	237 (46.3)	573 (47.5)	1.00	NA	–
PRESCRIPTION FACTORS
Total number of concurrent drugs, n (%)
<4	224 (32.2)	82 (16.0)	306 (25.4)	3.41 (2.43–4.82)	<0.001*	0.641
4–6	296 (42.6)	203 (39.6)	499 (41.3)	1.83 (1.39–2.42)	<0.001*	–
≥7	175 (25.2)	227 (44.3)	402 (33.3)	1.00	NA	–
Prescription days, n (%)
≤30	565 (81.3)	426 (83.2)	991 (82.1)	1.00	NA	0.638
>30	130 (18.7)	86 (16.8)	216 (17.9)	1.12 (0.82–1.53)	0.483	–
Single-dose packaging, n (%)
Yes	75 (10.8)	106 (20.7)	181 (15.0)	0.63 (0.44–0.89)	0.008*	0.637
No	620 (89.2)	406 (79.3)	1026 (85.0)	1.00	NA	–

The odds ratio (OR) and 95% confidence interval (CI) were calculated to predict the factors associated with non-adherence (PRR > 20%). Logistic regression models were adjusted for the total number of concurrent drugs, patient copayment, and nonuse of single-dose packaging.

^*Statistically significant at the 5% level. Adherence status: number (%).

PRR, prescription reduction ratio.