Abstracts & Commentary
Synopsis: The good news from OXVS is that community-wide risk factor modifications and preventive treatment are worth the effort, and that further reductions in stroke incidence are possible with more widespread stroke prevention programs.
Sources: Rothwell PM, et al. Change in Stroke Incidence, Mortality, Case-Fatality, Severity, and Risk Factors in Oxfordshire, UK From 1981 to 2004 (Oxford Vascular Study). Lancet. 2004;363:1925-1933. Feigin V, et al. How to Study Stroke Incidence. Lancet. 2004;363:1920-1921.
Rothwell and associates sought to determine whether implementation of preventive strategies in an aging population can offset the predicted rise in stroke incidence. They reported a population-based incidence study of Transient Ischemic Attack (TIA) and stroke that analyzed changes in rates, outcomes, and risk factors in Oxfordshire, United Kingdom over 20 years. They compared the results of the Oxfordshire Community Stroke Project1,2 (OCSP) of 1981-1984 with the present findings in the same community of the Oxford Vascular Study (OXVASC) of 2002-2004.
In OXVASC there were 476 patients with stroke or TIA, of which 262 strokes and 93 TIAs were initial events. Compared to the OCSP data, age-adjusted and sex-adjusted incidence of first-ever stroke fell by almost one-third; for primary intracerebral hemorrhage, incidence declined by more than one-half, but for subarachnoid hemorrhage, incidence was unchanged. Although 28% more initial strokes were expected in 2002-2004, compared to 1981-1984 due to demographic changes, namely a 33% increase in those aged 75 or older, the observed number fell (262 vs 286).
The incidence of disabling or fatal stroke declined, but there was no change in the core fatality rate (17.2% vs 17.8%). Age- and sex-adjusted relative risk did not change. Comparison of premorbid risk factors revealed substantial decreases in the proportion of smokers, mean total cholesterol, and mean systolic and diastolic blood pressures. In contrast, there were major increases in premorbid treatment with antiplatelet, antihypertensive, and lipid-lowering drugs.
Dr. Rothwell, with his associate Dr. Warlow, previously analyzed the heterogeneity of the effect of endarterectomy in the European Carotid Surgery Trial (ECST) population.3,4 The result was a predictive model that allowed clinicians to stratify patients according to risk of stroke and likelihood of surgical complications.
In editorial comments, Feigin and Vander Hoorn characterize Rothwell and associates’ present report as a "state-of-the-art" study that makes an important contribution to knowledge about the epidemiology of stroke. Above all, Rothwell et al provide welcome evidence that preventive strategies can reduce the incidence of stroke at the community level. Although Rothwell et al did not prove that the decline in stroke incidence was a direct result of changes in stroke risk factors, the size of the changes is consistent with such an effect. Furthermore, the measured increase in the use of preventive medications would be expected to produce a significant reduction in stroke incidence.
Rothwell et al noted a decline in the incidence of major stroke and incident fatal stroke but not in the case fatality of incident stroke. This finding can be explained by the fact that despite all the recent advances in acute stroke management, only 56% of acute stroke patients in Oxfordshire were hospitalized, and those who were admitted to hospital, were not cared for in dedicated stroke units.
Nevertheless, the good news from OXVS is that community-wide risk factor modifications and preventive treatments are worth the effort, and that further reductions in stroke incidence are possible with more widespread stroke prevention programs. — John J. Caronna
Dr. Caronna, Vice-Chairman, Department of Neurology, Cornell University Medical Center; Professor of Clinical Neurology, New York Hospital, is Associate Editor of Neurology Alert.
1. Bamford J, et al. J Neurol Neurosurg Psychiatry. 1990;53:16-22.
2. Dennis MS, et al. Stroke. 1989;20:333-339.
3. Rothwell PM, et al. Lancet. 1999;353:2105-2110.
4. Neurology Alert. 1999;17:93-94.