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Childhood intelligence and blood pressure in middle age

Robertson, J Ian S

Editorial Commentaries

Bowling, Glasgow, Strathclyde, UK.

Correspondence and requests for reprints to J. Ian S. Robertson, Elmbank, Manse Road, Bowling, Glasgow G60 5AA, Strathclyde, UK. Fax: +44 1389 890 291

See original paper on page 893

In elderly subjects, it is well-established that raised blood pressure is associated with a degree of mental impairment [1]. In part, this could be a consequence of lesions in arteries supplying the brain because hypertension would predispose to such insults. In accordance with those notions, antihypertensive therapy in old individuals has been shown to be accompanied by a diminished prevalence of dementia, albeit no effect was demonstrable on more subtle measures of intelligence [2].

Influences dating from much earlier in life could be responsible. Genetic aspects promoting hypertension would be likely to lead to mental impairment later in life via processes such as those outlined above. Alternatively, or additionally, certain genes might concurrently influence both intelligence and blood pressure, initially separately. Furthermore, there may be a link between the two, such as foetal programming. Some environmental aspects may also both raise blood pressure and impair cognition.

Several of these matters are addressed by Starr et al. [3] in the present issue of the journal. The authors studied data on 938 Scottish subjects, men and women, born in 1921. In 1932, when these individuals were schoolchildren, they were subjected to a well-validated mental ability test. Subsequently, between 1970 and 1976, they also participated in an epidemiological survey, which included blood pressure measurement under standardized conditions.

After adjustment for age, sex, social class, height, weight, blood cholesterol and smoking, it was found that for each standard deviation increase in childhood intelligence quotient (IQ), there was an average decrease in adult blood pressure of 3.15/1.5 mmHg.

Thus, not all of the mental impairment found in elderly hypertensive subjects can be attributed to brain damage consequent upon long-term exposure to raised arterial pressure. Starr et al. [3] have demonstrated a link between childhood intelligence and blood pressure in later life. Elucidating the mechanism(s) responsible for that association offers a fascinating prospect for future studies.

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References

1. Starr JM. Blood pressure and cognitive decline in the elderly. Curr Opin Nephrol Hyperten 1999; 8:247–351.
2. Forette F, Seux ML, Staessen JA, Thijs L, Birkenhäger W, Babarskiene MR, et al. Prevention of dementia in randomised double-blind placebo-controlled Systolic Hypertension in Europe (Syst-Eur) trial. Lancet 1998; 352:1347–1351.
3. Starr JM, Taylor MD, Hart CL, Davey Smith G, Whalley LJ, Hole DJ, et al. Childhood mental ability and blood pressure at midlife: linking the Scottish Mental Survey 1932 and the Midspan studies. J. Hypertens 2004; 22:893–897.
© 2004 Lippincott Williams & Wilkins, Inc.