The hydration influence on the risk of stroke (THIRST) study

There is a decreased sensation of thirst and often dehydration among the elderly population. It is unclear whether it represents a contributing factor for cerebral ischemic events.

Consecutive patients presenting to a University Hospital within 24 h of symptom onset, and a discharge diagnosis of acute ischemic stroke or transient ischemic attack in the year 2005, were identified. Healthy controls matched to gender, age, and presence of diabetes mellitus were obtained from the National Health and Nutrition Examination Survey (NHANES) 1999-2004. Calculated plasma osmolality of patients and healthy controls was compared in groups defined by age; > or =65 years and <65 years, before and after adjustment for possible confounders. Plasma osmolality comparisons were also made between subjects with and without diabetes mellitus or diuretic use. Within the patients group, comparisons were made according to stroke subtypes and time from symptom onset; < or =6 h vs. >6 h.

Plasma osmolality of patients > or =65 years was significantly higher than that of matched healthy controls, and the difference remained significant when we adjusted for potential confounders (295.4 vs. 292.3 mOsm/kg, difference 3.1, standard error (SE) 1.13, P = 0.006). Patients taking diuretics had higher plasma osmolality than patients not taking diuretics (296.0 +/- 8.0 vs. 292.4 +/- 8.0 mOsm/kg, P = 0.0026). Among patients, there was no difference between subgroups defined by stroke subtypes or time from symptom onset.

Elderly patients presenting with acute ischemic stroke or transient ischemic attack have high plasma osmolality levels, suggestive of volume depletion. This seems to be an early phenomenon and possibly a contributing factor to cerebral ischemia.