The influence of fluid intake on stroke recurrence--a prospective study

Recommended fluid intake is regarded as an important factor for stroke prevention. In mass media, drinking of at least 2000 ml water per day is recommended for any condition. However, no prospective trials are available which examined the impact of the amount of daily fluid intake on primary stroke prevention or on stroke recurrence. We performed a prospective study evaluating the daily fluid intake over a period of two years in stroke patients.

Patients (n=465) with a complete stroke (i.e., proven ischaemic cerebral infarction) were followed for two years with a regular visit every three months. At every visit the average daily amount of fluid intake was evaluated by a drinking diary. Patients had to protocol all kinds of fluid they were drinking during the day for a whole week. They were divided into two groups: daily intake of more and of less than 2000 ml. The rate of primary endpoint (stroke including transient ischaemic attack, myocardial infarction, or death from any cause) and of secondary endpoint (stroke) was calculated for the two groups. In addition, haemorheological parameters such as platelet reactivity, erythrocyte aggregation, and osmolarity were measured at every visit.

The mean observation period was 17 months. In this period, the patients with recommended fluid intake (mean amount 2427 ml) had a primary event rate of 12.3% whereas the patients with the low fluid intake (mean amount 1625 ml) had a primary event rate of 16.8%. The Kaplan-Meier analysis revealed a significantly better outcome of the patient group with recommended fluid intake with respect to the primary endpoint (p<0.013) and to the secondary endpoint (p<0.007). We observed a lower platelet reactivity in the patient group with recommended fluid intake as the only significant haemorheological factor influenced by the fluid intake. We observed no association between the amount of fluid intake and conventional vascular risk factors except a higher fluid intake in smokers.

Our data suggests that a fluid intake of more than 2000 ml per day might by a protective factor in secondary stroke prevention. A recommended fluid intake is associated with a lower platelet reactivity. No other haemorheological parameters were affected by the amount of fluid intake. However, advising patients after stroke on how much fluid they should drink is also influenced by other factors such as renal and cardiac function.