Underprescribing of cardiovascular therapies for diabetes in primary care

Objective: To determine the extent to which cardiovascular therapies are prescribed in primary care for those with diabetes, compared with those without diabetes.

Methods: Population study of patients with and without diabetes identified using a national primary care prescribing database. All patients receiving a prescription for any diabetes therapy., including insulin and oral bypoglycaemic drugs, or diagnostic test kit for glucose (n = 8523) and those receiving no such therapies (n = 145,756) during a 1-year period (September 1999-August 2000) in the Eastern Regional Health Authority of Ireland were identified. In addition, a sub-set of patients receiving a nitrate prescription, a marker for ischaemic heart disease (IHD), were also identified (n = 14,826). Odds ratios and 95% confidence intervals for prescribing of cardiovascular therapies between those with diabetes and those without, adjusted for age and ender, were calculated using logistic regression.

Results: The proportion of those (and 95% CES) with diabetes and IHD prescribed secondary preventative therapies was 37.3% (35.0, 39.6) for statins, 55.3% (53.0, 57.6) for angiotension converting enzyme inhibitors, 34.7% (32.5, 36.9) for beta blockers, 73.3% (71.2, 75.4) for aspirin, 4.4% (3.4, 5.4) for angiotensin-II antagonists and 2.5% (1.8, 3.2) for fibrates. The adjusted odds ratios for prescribing in those with diabetes compared with those without are 1.44 (1.30, 1.61) for statins, 3.09 (2.79, 3.42) for angiotension converting enzyme inhibitors, 0.82 (0.74, 0.91) for beta blockers, 1.23 (1.09, 1.38) for aspirin, 1.47 (1.13, 1.87) for angiotensin-II receptor blockers and 4.23 (2.88, 6.14) for lipid-lowering fibrates.

Conclusion: The greater rate of prescribing of cardiovascular therapies in those with diabetes relative to those without is not unexpected given the higher risk of coronary heart disease in those with diabetes. However, the proportion of patients with diabetes, particularly those with established IHD, prescribed cardiovascular therapies is considerably below that recommended in local and international guidelines.