Researchers in a new study have said that an elderly person's ability to think clearly and the ability to recall simple information deteriorates when their blood pressure goes high.

The findings are based on a small study of 36 women and men in the age bracket of 60 to 87. The researchers had the participants measure their blood pressure and complete mental function tests every morning and evening for 60 days in a row and they found that the performance went down as the blood pressure went up. The higher the blood pressure the more mistakes were made.

Inductive reasoning which allows you to make generalizations based on specific instances was the task that was linked to blood pressure. In the test the participants were asked to identify a pattern in a series of letters and predict the next letter in the series.

Dr Jason Allaire, an assistant professor of psychology at North Carolina State University in Raleigh who co-authored the study said, "This means that stressful situations may make it more difficult for some seniors to think clearly."

What causes the high blood pressure to reduce mental ability is not known though previous studies have also found that elderly people with high blood pressure have poorer mental skills than those with normal blood pressure. The stress of trying to cope with a mental task can also raise the blood pressure and therefore be a link.

The research has established that sufferers should be extra vigilant about managing their condition and avoiding stress. Allaire said, "If you have high blood pressure it is really important to get it under control."

The effect of blood pressure was only seen when a person's systolic blood pressure (the first or top number) was 130 or higher. A reading of 120 to 139 is considered borderline high blood pressure and blood pressure is considered high when the systolic blood pressure reaches 140 or the diastolic blood pressure reaches 90.

Dr Allaire said that the effect was only seen in people with higher than average blood pressure to start with. Study subjects whose average blood pressure was low or normal saw no change in their cognitive functioning even when their blood pressure shot up.

The study appears in the current issue of the Journal of Gerontology: Psychological Sciences.