Elevated CRP is phenotype for familial preserved cognition

By Andrew Czyzewski, medwireNews Reporter

The first-degree relatives of very old people with preserved cognition and elevated C-reactive protein (CRP) have a low risk for developing dementia, research shows.

The results are in contrast to previous observations in young-elderly samples (aged <75 years) where elevated CRP actually increased the risk for developing dementia.

Jeremy Silverman (Mount Sinai School of Medicine, New York, USA) and study co-authors nevertheless invoke a theory whereby CRP may be a phenotype for familial, and thus possibly genetic, successful cognitive aging.

"Several investigators have proposed that protective genotypes or other protective factors may 'buffer' the effects of risk factors, and aging per se, on dementia and death," they comment in Neurology.

The present study included a primary sample of 1329 parents and siblings of 277 cognitively intact male veteran probands, aged at least 75 years; and a replication sample of 202 relatives of 51 cognitively intact community-ascertained probands aged at least 85 years.

Silverman and colleagues found that, after adjusting for proband's age, proband's years of education, and relative's gender, a higher log-transformed CRP in probands was strongly associated with lower risk for dementia in relatives, at a hazard ratio (HR) of 0.55.

A similar, but stronger, association was found in the replication sample, where relatives of the probands (aged over 85 years) had an even lower risk for dementia (HR=0.15).

"The similar direction of these results - despite several differences between the samples - nominates high CRP in individuals with successful cognitive aging as a phenotype for familial successful cognitive aging," Silverman et al observe.

With respect to the previous divergent findings showing CRP as a dementia risk factor, Silverman and team say this can be readily explained by epidemiologic mechanisms.

"The reduced number of unprotected individuals surviving with intact cognition will tend to have low risk factor levels, which contributed to their survival and intact cognition.

"In contrast, protected subjects are more likely to survive, and to have intact cognition, even at high risk factor levels," they comment.

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