In the MediPlus database, 43,486 patients had a diagnosis of type 2 diabetes. Of the 11,543 who had their first observed diagnosis between 2003 and 2005, 9,158 patients (54% male) met the inclusion criteria for this analysis. Mean (SD) age was 62.4 (12.8) years, with 9.6%, 44.3%, 27.5%, and 18.6% of patients within the 30- < 45, 45- < 65, 65- < 75, 75+ age groups, respectively (Table ). HbA1c values were available for 55% (n/N = 5,044/9,158) of the entire cohort. There was no association between age and missing HbA1c values (p = 0.3876 for trend using chi-square test). Mean (SD) HbA1c at diagnosis was 8.1% (2.3) for the cohort of patients with HbA1c values, and 8.7% (2.4), 8.3% (2.3), 8.0% (2.2), and 7.7% (2.0) for those in the 30- < 45, 45- < 65, 65- < 75, 75+ age groups, respectively. The presence of pre-existing co-morbid conditions at baseline increased with age, except for liver disease where the opposite was observed (Table ). During the follow-up period, newly diagnosed co-morbid conditions included cardiovascular conditions (5.7%), microvascular complications of diabetes (7.2%), cancer (1.8%), edema (1.7%), liver disease (0.5%), and Alzheimer's disease/dementia (0.2%). Use of antihypertensive and gastroprotective agents increased with age, whereas use of lipid-modifying agents was similar across age groups (Table ). Newly prescribed medications during the follow-up included antihypertensive (10.1%), lipid-modifying (28.6%), weight-reducing (1.6%), and gastroprotective agents (6.3%).
Baseline characteristics of patients with newly diagnosed type 2 diabetes during the index period
Overall, 36%, 42%, and 51% of patients initiated antihyperglycaemic therapy within 180 days, 1 year, and 2 years of diagnosis, respectively. The proportion of patients who had treatment initiated within 2 years of diagnosis decreased with advancing age (65%, 55%, 46%, and 40% for patients in the 30- < 45, 45- < 65, 65- < 75, 75+ age groups, respectively). The median time to treatment initiation increased with advancing age (213, 530, > 730, and > 730 days for patients in the 30- < 45, 45- < 65, 65- < 75, 75+ age groups, respectively [Figure ]). Among the treated patients, median (25th, 75th percentile) time to treatment initiation was 63 (8, 257) days, with treatment initiation increasingly delayed with age. Of the treatments prescribed, 76% of patients were prescribed metformin, 19% sulphonylurea, 4% insulin, and 1% other. Metformin use decreased with age (77%, 82%, 76%, and 66%, for patients in the 30- < 45, 45- < 65, 65- < 75, 75+ age groups, respectively; p < 0.0001 for trend using chi-square test) and sulphonylurea use increased with age (15%, 15%, 22%, and 32%, respectively; p < 0.0001 for trend using chi-square test).
Kaplan-Meier curves for time to initiation of antihyperglycaemic therapy after diagnosis of type 2 diabetes by age group.
Cox regression analysis adjusting for patients' baseline characteristics showed that increasing age was associated with longer time to initiation of antihyperglycaemic medication (Table ). An HbA1c ≥ 7.5% at diagnosis was associated with shorter time to treatment initiation (Table ). In this cohort of patients (i.e., HbA1c ≥ 7.5% at diagnosis, n = 2,446), 73%, 81%, and 87% initiated antihyperglycaemic therapy within 180 days, 1 year, and 2 years of diagnosis, respectively. There was a significant interaction between age and HbA1c at diagnosis such that the negative effect of age on treatment initiation was reduced in individuals with higher HbA1c values at diagnosis, i.e., ≥ 7.5% (Table ). Other significant predictors associated with shorter time to antihyperglycaemic medication initiation included female gender, use of lipid-modifying agents, use of weight-reducing agents and later physician registration year. The missing indicator for HbA1c values was associated with shorter time to initiation (Table ). During the follow-up period, development of cardiovascular conditions (Table ), hospitalization, and new use of antihypertensive, lipid-modifying, gastroprotective, or weight-reducing agents were associated with shorter times to treatment initiation (Table ).
Adjusted hazard ratios for initiation of antihyperglycaemic treatment
Figure illustrates that higher HbA1c values at the end of follow up were associated with lower levels of non-treatment with antihyperglycaemic medications. Within each HbA1c category there was a significant trend for patients in the older age groups to remain untreated (Figure ). Among those untreated, the proportion of patients with an HbA1c ≥ 7.5% was not statistically different across age groups (p > 0.05).
Proportion of patients untreated with antihyperglycaemic medication after the 2-year follow-up period by age group and last available HbA1c value.