Anti-Hyperglycemic Medication Adherence and Health Services Utilization in People with Diabetes: A Longitudinal Study of Alberta’s Tomorrow Project

Figures & data

Figure 1 Anti-hyperglycemic medication adherence profile after diagnosis. Patients were grouped based on whether or not taking anti-hyperglycemic medication and adherence levels by proportion of days covered (PDC) categories (adherent: PDC≥0.8, non-adherent: PDC <0.8). The percentage of patients taking anti-hyperglycemic medication and the average PDC score were summarized for each year from diagnosis (Year 1) to Year 16.

Table 1 Rate of Healthcare Utilization in the Subsequent 12 Months by Anti-Hyperglycemic Medication Status (n=2155)^†

	No Medication			Adherent			Non-Adherent
	Freq.	P-Y	IR	Freq.	P-Y	IR	Freq.	P-Y	IR
All-cause hospitalization	1049	6092.1	0.172	1193	7342.3	0.162	176	676.5	0.260**
DM-specific hospitalization	10	6092.1	0.002*	26	7342.3	0.004	20	676.5	0.030**
ACS hospitalization	111	6092.1	0.018*	156	7342.3	0.021	35	676.5	0.052**
ED visits	4155	6092.1	0.682*	5349	7342.3	0.729	705	676.5	1.042**
GP visits	44,061	6092.1	7.232*	57,271	7342.3	7.800	5875	676.5	8.684**

Notes: ^†Patients were grouped based on whether or not they were taking anti-hyperglycemic medication and by adherence levels (via proportion of days covered [PDC] categories, adherent: PDC≥0.8, non-adherent: PDC <0.8); due to the time-varying nature of drug adherence, patient’ data was segmented by every 12 months. Frequency was computed as the accumulated number of healthcare utilization events of each drug adherence category over the total follow-up of 15 years for all the segments; person-year (P-Y) is the accumulated person-years of each drug adherence category over the total follow-up of 15 years for all segments. *Statistically significant (p<0.05) difference between patients with no anti-hyperglycemic medication (reference group) vs adherent or non-adherent patients; **Statistically significant (p<0.05) difference between adherent vs non-adherent patients.

Abbreviations: P-Y, person-years; IRR, incidence rate ratio; DM, diabetes; ACS, ambulatory care sensitive conditions; ED, emergency department; GP, general practitioner.

Table 2 Association Between Anti-Hyperglycemic Medication, Drug Adherence and Healthcare Utilization in the Subsequent 12 Months in Patients with Diabetes: Results from Multivariable Negative Binomial Regression Analysis*

	IRR	95% CI	p-value	IRR	95% CI	p-value
n=2155	All-cause hospitalization
Medication status**
No medication	Ref	-	-	-	-	-
Adherent	1.09	0.99–1.22	0.08	Ref	-	-
Non-adherent	1.62	1.33–1.97	<0.001	1.48	1.22–1.79	<0.001
	DM-specific hospitalization
Medication status**
No medication	Ref	-	-	-	-	-
Adherent	2.62	1.20–5.72	0.02	Ref	-	-
Non-adherent	12.39	5.23–29.33	<0.001	4.73	2.38–9.40	<0.001
	ACS hospitalization
Medication status**
No medication	Ref	-	-	-	-	-
Adherent	1.46	1.10–1.94	0.008	Ref	-	-
Non-adherent	2.94	1.88–4.60	<0.001	2.01	1.31–3.07	<0.001
	ED visits
Medication status**
No medication	Ref	-	-	-	-	-
Adherent	1.10	1.03–1.18	0.003	Ref	-	-
Non-adherent	1.43	1.26–1.63	<0.001	1.30	1.15–1.47	<0.001
	GP visits
Medication status**
No medication	Ref	-	-	-	-	-
Adherent	1.14	1.09–1.19	<0.001	Ref	-	-
Non-adherent	1.34	1.23–1.45	<0.001	1.17	1.08–1.27	<0.001

Notes: *Incident rate ratio (IRR) was estimated using multivariable negative binomial regression models, after adjusting for age at diagnosis (35–44yr, 45–64yr, 65+yr), sex (male/female), ethnicity (Caucasian vs other), rural vs urban, education attainment (secondary or less, some post-secondary, post-secondary), BMI categories (under/normal, overweight, obesity), current smoking status (yes/no), physically active (yes/no, based on whether or not accumulating at least 210 min moderate-to-vigorous intensity recreational physical activities per week in the past 12 months), tertiles of Healthy Eating Index Canada score for diet quality assessment, previous healthcare utilization after diagnosis, and Elixhauser comorbidities (0, 1–2, 2+); **Patients were grouped based on whether or not they were taking anti-hyperglycemic medication and by adherence levels (via proportion of days covered [PDC] categories, adherent: PDC≥0.8, non-adherent: PDC <0.8).

Abbreviations: P-Y, person-years; IRR, incidence rate ratio; CI, confidence interval; DM, diabetes; ACS, ambulatory care sensitive conditions; ED, emergency department; GP, general practitioner.

Table 3 Past 12 Months Drug Adherence and Healthcare Utilization in the Subsequent 12, 36 and 60 Months: Sub-Group Analysis of Patients with at Least 72 Months of Follow-Up*

	Subsequent 12 Months			Subsequent 36 Months			Subsequent 60 Months
	IRR	95% CI	p-value	IRR	95% CI	p-value	IRR	95% CI	p-value
n=1477	All-cause hospitalization
PDC levels
≥0.8	Ref	-	-	Ref	-	-	Ref	-	-
<0.8	1.75	1.36–2.27	0.002	1.18	0.98–1.39	0.07	1.05	0.94–1.18	0.35
	DM-specific hospitalization
PDC levels
≥0.8	Ref	-	-	Ref	-	-	Ref	-	-
<0.8	6.01	2.21–16.35	<0.001	3.21	1.63–6.33	0.001	3.01	1.83–4.94	<0.001
	ACS hospitalization
PDC levels
≥0.8	Ref	-	-	Ref	-	-	Ref	-	-
<0.8	2.32	1.35–43.99	0.002	1.25	0.86–1.81	0.25	1.14	0.88–1.47	0.31
	ED visits
PDC levels
≥0.8	Ref	-	-	Ref	-	-	Ref	-	-
<0.8	1.43	1.20–1.69	<0.001	1.12	0.99–1.27	0.06	1.07	0.96–1.18	0.21
	GP visits
PDC levels
≥0.8	Ref	-	-	Ref	-	-	Ref	-	-
<0.8	1.23	1.10–1.38	<0.001	1.12	1.01–1.22	0.03	1.08	0.99–1.16	0.07

Notes: *Incident rate ratio (IRR) was estimated using multivariable negative binomial regression models, after adjusting for age at diagnosis (35–44yr, 45–64yr, 65+yr), sex (male/female), ethnicity (Caucasian vs other), rural vs urban, education attainment (secondary or less, some post-secondary, post-secondary), BMI categories (under/normal, overweight, obesity), current smoking status (yes/no), physically active (yes/no, based on whether or not accumulating at least 210 min moderate-to-vigorous intensity recreational physical activities per week in the past 12 months), tertiles of Healthy Eating Index Canada score for diet quality assessment, previous healthcare utilization after diagnosis, and Elixhauser comorbidities (0, 1–2, 2+).

Abbreviations: P-Y, person-years; IRR, incidence rate ratio; CI, confidence interval; DM, diabetes; ACS, ambulatory care sensitive conditions; ED, emergency department; GP, general practitioner.