Background Ischaemic stroke and ischaemic heart disease (IHD) are well known complications of diabetes mellitus (DM). It is assumed that better control of blood glycaemia would decrease the occurrence of these complications. In the general population of England the prevalence of DM is increasing and the incidence of stroke and IHD is declining. We were interested in determining whether the excess risk of ischaemic stroke and IHD in people with DM has declined over time.
Methods We used English national linked Hospital Episode Statistics for 1999–2011. The outcomes of interest were hospitalisation and death from ischaemic stroke and IHD. We compared the rates of ischaemic stroke and IHD in the cohort of patients with DM with the rates in a diabetes-free control cohort. Results were expressed as a rate ratio (RR) standardised for age and for a range of other variables. RRs were calculated for each of the successive 4-year intervals. We selected cases based on ICD codes. The ICD 10 codes were E10-E14 for DM, I63 for ischaemic stroke, and I20-I25 for IHD. Only patients with a primary diagnosis of DM were included, to avoid case mix bias that might potentially arise from other co-morbidities.
Results In total there were 5666 and 32,409 patients with a primary diagnosis of DM who developed ischaemic stroke or IHD, respectively. The RRs for subsequent ischaemic stroke in people with DM were 2.43 (95% CI 2.35–2.51) in 1999–2002, 2.38 (2.25–2.51) in 2003–2006, and 2.34 (2.14–2.54) in 2007–2011. RRs for IHD in people with DM were 2.63 (2.59–2.66) in 1999–2002, 2.37 (2.31–2.42) in 2003–2006, and 2.37 (2.28–2.47) in 2007–2011.
Conclusion There was no decline in the excess risk, when compared to the control population, of ischaemic stroke in patients with DM over the last 13 years. A modest decline was observed in the excess risk of IHD between 1999–2002 and 2003–2006, but this improvement has not continued in recent years. These findings show that diabetes remains an important risk factor for stroke and IHD. They suggest that there were no major improvements in preventing these complications of DM at a population level in England.