Telomere length linked to dementia risk

NEW YORK, Nov 23 (Reuters Health) - Reading a cellular biological clock could one day help identify people at risk of developing dementia and other conditions decades before they reach old age, according to German scientists.

What's more, the researchers believe that antioxidants may prevent this age-related deterioration.

The clock in question is based on the telomere, a snippet of genetic material found at the end of the chromosome. Each time that a cell divides, a portion of the telomere is lost. When the telomere reaches a certain length, it triggers a cell-suicide program and the cell dies.

Dr. Thomas von Zglinicki of the Evangelische Geriatriezentrum Berlin and colleagues found a strong association between telomere length--how much time is left on this biological clock--and vascular dementia, a type of brain damage caused by blood vessel disease.

The investigators measured the telomeres in white blood cells collected from 186 people, including 149 people aged 55 and older. Forty-one of the patients had confirmed vascular dementia.

Individuals with shorter telomeres in their blood cells were three times more likely to have vascular dementia, but those with longer telomeres were 100 times less likely to have vascular dementia. Telomeres generally get shorter with age.

People with Alzheimer's disease, as well as those with blood vessel disease but no dementia, did not have short telomeres, according to the findings published in the journal Laboratory Investigation.

The researchers suggest that telomere length is a marker for a person's ability to withstand oxidative stress, a process in which by-products of normal metabolism damage cells and DNA. Oxidative stress plays a major role in the ageing process.

In human cells, the investigators found, the rate at which telomeres shortened correlated with the cells' ability to withstand oxidative damage. Cells that were more vulnerable to oxidative damage had telomeres that shortened more quickly, while cells that were more able to resist this damage had a slower rate of telomere shortening.

There is currently no way to predict who will develop vascular dementia, the second leading cause of dementia in the developed world after Alzheimer's disease. However, von Zglinicki suggests that telomere length could one day be used to identify people at risk of this condition.

While measuring the length of telomeres is currently a time-consuming process, with enough demand it would be possible to develop techniques to make it easier, the report indicates. The logical strategy for prevention, von Zglinicki added, would be long-term therapy with antioxidants.

He cautioned that much more research is needed to confirm these findings.

"One problem is that the efficiency of single antioxidants is questionable at best. The other (problem) is, we are talking here really long-term, probably decades," he said. "There is no experience about such long-term side effect of antioxidants. In the end, it comes to decisions regarding lifestyle and, if you like, a means to monitor the cumulative effect of it."