Among people aged 85 and older, low blood pressure is associated with increased mortality, Finnish researchers report.

The finding applies specifically to the upper or systolic reading of blood pressure, produced when the heart contracts. A reading of 140 is considered the start of excessively high blood pressure normally, but among the elderly in this study blood pressure below 140 was linked to a greater likelihood of dying over a given period.

“The biological reasons for the association need to be examined in further studies,” Dr. Tuula Pirttila” told Reuters Health. “It is possible that low blood pressure was a sign of decreased vitality and poor health in some subjects, but this is not the whole explanation.”

Pirttila” pointed out that high blood pressure, “particularly in middle age, is a known risk factor for cardiovascular mortality and also for cognitive decline. However, there are few studies in the very old (85+).”

It could be, the researcher continued, that “the very old represent a select group of individuals and it is evident that bodily functions and physiological responses, for example to drugs, are different. As the population in the western societies gets older and particularly the group of very old increases, it is important to get more knowledge of the factors contributing to their health. There are not many population-based studies that have concentrated on the very old.”

Pirttila”, from Kuopio University Hospital in Finland, and colleagues studied the association between blood pressure and mortality in 521 residents of the city of Vantaa who were 85 years of age or older in 1991. During 9 years of follow up, 479 died.

After adjusting for other factors, there was a strong link between low systolic blood pressure and deaths from any cause, the team reports in the Journal of the American Geriatrics Society.

The likelihood of dying was highest in individuals with systolic blood pressure less than 140, while it tended to be lower in those with a reading of 160 or greater.

“Sufficiently high blood pressure may be necessary to guarantee adequate cardiac and cerebral perfusion,” the investigators suggest.

Pirttila” told Reuters Health that it might be necessary to reconsider the need to treat high blood pressure if someone is very old. Results of clinical trials that have been performed in “considerably younger subjects can not be generalized for this group.”

SOURCE: Journal of the American Geriatrics Society, June 2006.