01 August 2013

Anaemia indicates dementia risk in seniors

Among people in their 70s, anaemia may indicate an increased risk of developing dementia later in life, according to a new study.

Among people in their 70s, anaemia may flag an increased risk of developing dementia later in life, according to a new study.

Researchers following more than 2 500 US adults in their 70s for over a decade found that those who started out with anaemia were 65% more likely to develop dementia by the end of the study period.

"Anaemia is common in the elderly and occurs in up to 23% of adults ages 65 and older," said senior author Dr Kristina Yaffe of the University of California, San Francisco. People with anaemia lack enough healthy red blood cells to carry oxygen throughout the body.

Fewer healthy red blood cells could mean less oxygen travelling to the brain and may result in cognitive decline, she said. Several conditions, including kidney disease and nutritional deficiencies, can cause anaemia.

Previous studies have found an association between anaemia and dementia, but they had not followed anaemic adults over time to see if they developed cognitive problems, as the current study did, Yaffe told Reuters Health.

The study

She and her co-authors used medical records to follow 2 552 people between the ages of 70 and 79 at the beginning of the study period. They were tested for anaemia early in the study and given memory and thinking tests over a total of 11 years.   At the start of the study, 393 participants had anaemia.

At the end of the study, 445, or about 18% of participants, had developed dementia, based on records of their hospital visits, prescribed dementia medication use or a significant downward change on the memory and thinking tests. Of the roughly 400 men and women who were anaemic at the start, 23% developed dementia, compared to 17% of the 2 000 others who were not anaemic, according to the results published in the journal Neurology.

That 6% difference is a large change in risk on a population level, Yaffe said. "I think doctors should be aware of this important connection, especially as both anaemia and dementia are common in ageing," she said.

The increased risk for dementia linked to anaemia did not change based on race or gender. Despite the association, the study does not prove that anaemia causes dementia, cautioned Dr Ruth Peters, who researches risk factors for dementia at Imperial College London and was not involved in the new study.

"There are many risk factors that are associated with dementia and these kinds of studies are very useful in identifying and clarifying these," she told Reuters Health by email.

Each individual will have their own mosaic of risk factors. "It is possible that a third influence, like chronic kidney disease, caused both anaemia and dementia in the participants with both conditions, but the authors tried to rule that out," Yaffe said.

Low iron
Low iron levels, which are one cause of anaemia, can cause heart problems for older people, so doctors usually check iron and recommend getting more of it from foods like spinach or over the counter vitamins if levels are low, she said.

"However, a third of the time, doctors cannot find a common cause for the lower haemoglobin levels (anaemia) in older adults," said Dr Raj Shah of Rush University Medical Center in Chicago.

Anaemia can also result from poor nutrition, bleeding disorders or cancer, among other things, said Shah, who studies cognitive decline in older people but was not involved in the study. "We still have to understand what is the mechanism by which low haemoglobin is associated with cognitive decline and risk of developing dementia in older persons," Shah told Reuters Health. Future research should investigate whether correcting anaemia also improves cognitive health, Yaffe said.


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