Blood pressure and cognitive decline in the elderly

Regulation of axonal development by natriuretic peptide hormones

Natriuretic peptides (NPs) are a family of cardiac- and vascular-derived hormones that are well known for regulating blood pressure, but their expression in the brain poses an intriguing yet unanswered question concerning their roles in the nervous system. Here, we report several unique activities of these hormones in regulating axonal development of dorsal root ganglion (DRG) neurons in the spinal cord. First, the C-type NP (CNP) is expressed in a restricted area of the dorsal spinal cord and provides a cue that is necessary for bifurcation of central sensory afferents. Second, in the culture of embryonic DRG neurons, CNP stimulates branch formation, induces axon outgrowth, and attracts growth cones. Furthermore, these activities are mediated by cyclic guanosine-3',5'-monophosphate (cGMP) signaling and can be elicited by other members of NP hormones. Thus, NPs represent a new class of extracellular factors that regulate key axonal processes during development. Because their receptors are present in many regions of the embryonic and adult brain, we propose that these hormones have wide influence on the development and function of the nervous system.

Childhood mental ability and blood pressure at midlife: linking the Scottish Mental Survey 1932 and the Midspan studies

OBJECTIVES

To establish the relationship between childhood mental ability and adult hypertension.

DESIGN

Retrospective cohort study.

SETTING

Community.

PARTICIPANTS

Non-clinical sample of people born in 1921 who participated in both the Scottish Mental Survey 1932 and the Midspan studies. Nine hundred and thirty-eight people were participants in both studies.

MAIN OUTCOME MEASURES

Mid-life systolic and diastolic blood pressure, intelligence quotient (IQ) at age 11 years, sex, social class, height and weight.

RESULTS

After adjustment for age, sex, social class, body mass index, height, cholesterol level and smoking, there remained a 3.15 mmHg decrease in systolic blood pressure and a 1.5 mmHg decrease in diastolic blood pressure for each standard deviation increase in childhood IQ.

CONCLUSIONS

The association between hypertension and lower cognitive function in adulthood is partly accounted for by individual differences in childhood IQ.

Cerebral white matter abnormalities and lifetime cognitive change: a 67-year follow-up of the Scottish Mental Survey of 1932

Cerebral white matter abnormalities relate to cognitive functioning in elders. We examine whether this association is (a) independent of mental ability in youth and (b) related to general and/or specific mental abilities. We retested 83 participants of the Scottish Mental Survey of 1932 on a battery of mental tests. Their brains were scanned by magnetic resonance imaging. Three independent ratings (Fazekas) were made of periventricular, and subcortical and deep white matter abnormalities. Structural equation models showed that, irrespective of brain location, white matter abnormalities contributed about 14% of cognitive function variance in old age. Some of this effect might be due to hypertension. This contribution is independent of mental function in early life and is associated with general cognitive ability.

Are antihypertensive agents protective against dementia? A review of clinical and preclinical data

In the United States, the size of the population of persons aged 65 years or older is expected to double within the next 30 years, resulting in a marked increase in the prevalence of dementia. Hypertension is a risk factor for cognitive impairment and dementia in addition to cerebrovascular morbidity and mortality. The evidence for a connection between high blood pressure in midlife and dementia in late life comes from numerous longitudinal studies. A placebo-controlled, double-blind, randomized trial involving 2,418 patients aged 60 years or older with isolated systolic hypertension demonstrated that active treatment based on the dihydropyridine calcium antagonist nitrendipine with the addition of enalapril, hydrochlorothiazide, or both if needed to control systolic blood pressure to <150 mmHg, significantly reduced not only stroke and cardiovascular complications but also the incidence of vascular dementia and Alzheimer's disease. Several trials of antihypertensive treatment are ongoing to confirm this important finding. The newer dihydropyridine calcium antagonists lacidipine and lercanidipine are effective and well tolerated in the treatment of hypertension. In animal models, these newer agents also have been shown to prevent the progression of hypertensive microvascular damage. Their neuroprotective effects offer possible unique advantages in the management of hypertension.

The relationship between temporal changes in blood pressure and changes in cognitive function: atherosclerosis risk in communities (ARIC) study

BACKGROUND

Although previous epidemiological studies have reported that hypertension is a major risk factor for decline in brain perfusion and atrophy, which are known to be related to cognitive decline, the impact of temporal changes in blood pressure on age-related cognitive declines has not been assessed.

METHODS

The present study evaluates changes in blood pressure and cognitive decline over a 6-year period in the Atherosclerosis Risk in Communities (ARIC) Study. This report is based on 8,058 men and women aged 48-67 years examined in the second (1990-92), and fourth (1996-98) ARIC cohort visits. Changes between these visits were measured in hypertension status and three cognitive function tests: Delayed Word Recall (DWR), the Digit Symbol Subtest of the Wechsler Adult Intelligence Scale-Revised (DSS/WAIS-R), and the Word Fluency (WF). Adjusted mean differences in cognitive function were compared among five categories of hypertension status by using linear regression modeling.

RESULTS

In the present study, older subjects with uncontrolled hypertension had a significantly larger mean DSS/WAIS-R score decline than normotensive subjects. Although other cognitive declines did not achieve statistical significance, both cross-sectional and change analysis suggested that partially controlled or uncontrolled hypertension is associated with a less favorable cognitive profile, particularly when considering results of the DSS and the WF tests.

CONCLUSIONS

The present study results provide some support to the hypothesis that hypertension status changes over 6 years in individuals initially aged 48-67 years are related to cognitive changes.