The importance of hypertension in the aetiology of infarctive and haemorrhagic stroke. The Lower Hunter Stroke Study.

OBJECTIVE

To determine the importance of hypertension in the aetiology of infarctive and haemorrhagic stroke in persons aged 35-69 years.

DESIGN

A population-based case-control study.

SETTING

Lower Hunter Region community.

SUBJECTS

One hundred and ninety patients with a first stroke were identified from a register, including all hospital admissions and death certificates in the Region, and compared with 496 control subjects obtained from a random population sample of the same community.

MAIN OUTCOME MEASURE

First event of stroke (fatal or non-fatal).

RESULTS

Twenty-seven per cent of those with a haemorrhagic stroke, compared with 2% of those with infarctive stroke, died before hospital admission; the in-hospital mortality was 15% and 9%, respectively. Twenty-one per cent of control subjects, compared with 51% of those with stroke, were currently receiving treatment for hypertension. By logistic regression analysis the odds ratio for receiving current treatment for hypertension in those with haemorrhagic stroke was 5.5 (95% confidence interval [CI], 2.36-12.8), compared with 2.53 (95% CI, 1.48-4.34) in those with infarctive stroke. Other differences between haemorrhagic and infarctive stroke included no excess risk in men for haemorrhagic stroke but an odds ratio of 3.51 (95% CI, 1.83-6.74) for infarctive stroke; and a steep risk gradient for obesity in haemorrhagic but not in infarctive stroke. Cigarette smoking carried a non-significant odds ratio of around 1.5, with no difference between stroke type. Among those who had ever been told that they had hypertension, 75% and 71% of patients with infarctive stroke and haemorrhagic stroke, respectively, and 61% of control subjects, were currently receiving treatment for hypertension. In those stroke patients who were currently being treated for hypertension, 63% had a pre-admission diastolic blood pressure of 90 mmHg or more. The mean diastolic blood pressure levels on admission were 10 mmHg higher than the latest recorded pre-hospital measurements and fell to 10 mmHg lower than the levels recorded before hospital admission by the time of discharge.

CONCLUSION

Hypertension is important in the aetiology of both infarctive and haemorrhagic strokes, although it may be more important in haemorrhagic stroke, and there appear to be other aetiological differences between stroke types. Most of the patients with a history of hypertension were currently receiving treatment for hypertension, although blood pressure control before admission was not optimal.