Abstract
The relation between hypertension and cognition in elders remains unclear, and studies on the effect of antihypertensive drugs on cognition have demonstrated conflicting results. This study was performed to evaluate if the association between hypertension and cognition in elders differed depending on serum concentrations of organochlorine (OC) pesticides, common neurotoxic chemicals. Participants were 644 elders aged 60–85 years who participated in the National Health and Nutrition Examination Survey 1999–2002 and were able to complete a cognitive test. We selected 6 OC pesticides that were commonly detected in the elderly. Cognition was assessed by the Digit Symbol Substitution Test (DSST), a relevant tool for evaluating hypertension-related cognitive function, and low cognition was defined by the DSST score < 25th percentile. When OC pesticides were not considered in the analyses, elders with hypertension had about 1.7 times higher risk of low cognition than those without hypertension. However, in analyses stratified by serum concentrations of OC pesticides, the associations between hypertension and low cognition were stronger the higher the serum concentrations of p,p’-DDT, p,p’-DDE, β-hexachlorocyclohexane, and trans-nonachlor increased. Among elders in the 3rd tertile of these pesticides, adjusted odds ratios were from 2.5 to 3.5. In contrast, hypertension was not clearly associated with the risk of low cognition in elders in the 1st tertile of these pesticides. Similar patterns were observed for the continuous DSST score dependent variable. The difference in the association between hypertension and DSST scores according to the levels of OC pesticides suggest a key role of OC pesticides in the development of hypertension-related cognitive impairment and may help to identify hypertensive elders who are at a high risk of cognitive impairment.
Highlights
High blood pressure in midlife is associated with an increased risk of dementia, including Alzheimer's disease and vascular dementia, through accelerating arteriosclerotic changes in the brain [1]
When OC pesticides were not considered in the analyses, elders without hypertension had a higher score by about 3.8 points than those with hypertension (P < 0.01)
When we performed stratified analyses by serum concentrations of OC pesticides, the association between hypertension and Digit Symbol Substitution Test (DSST) score generally became stronger as serum concentrations increased
Summary
High blood pressure in midlife is associated with an increased risk of dementia, including Alzheimer's disease and vascular dementia, through accelerating arteriosclerotic changes in the brain [1]. Randomized controlled studies have demonstrated heterogeneous effects of blood pressure lowering on cognitive function [2]. At present, it is unknown whether there is any modifying effect of other variables on the relationship of blood pressure with cognition which may be helpful in interpreting inconsistent results in elders. Some OC pesticides were associated with accelerated aging-related cognitive impairment [6]
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