Global Impact Could Multiply As The Population Continues to Age
Having Alzheimer's disease may increase the risk of getting other potentially disabling health conditions, including seizures and anemia, according to new research presented today at the Alzheimer's Association International Conference on Alzheimer's Disease 2010 (AAICAD 2010) in Honolulu, HI.
"Alzheimer's disease is a global health crisis with devastating effects on individuals, families, and national healthcare systems," said William Thies, PhD, Chief Medical and Scientific Officer at the Alzheimer's Association. "If, in fact, Alzheimer's also increases risk of other disabling conditions, then its impact may be more devastating than we've envisioned as the global population ages and as more countries become westernized in their habits and lifestyles."
According to the 2009 World Alzheimer Report from Alzheimer's Disease International, a London-based nonprofit, international federation of 71 national Alzheimer organizations including the Alzheimer's Association, the number of people with Alzheimer's or another dementia, currently 35 million, is expected to nearly double every 20 years, to 65.7 million in 2030 and 115.4 million in 2050.
Worldwide, the economic cost of dementia has been estimated as $315 billion annually. (Wimo, et al. "An Estimate of the Total Worldwide Societal Costs of Dementia in 2005." Alzheimer's & Dementia: The Journal of the Alzheimer's Association. Vol. 3, Issue 2, April 2007.)
Alzheimer's is Associated with Increased Incidence of Seizures
Some small studies have shown Alzheimer's to be a risk factor for seizures. H. Michael Arrighi, PhD, of Janssen Alzheimer Immunotherapy Research & Development; Nicole Baker, MPH, Pfizer; and colleagues conducted an observational study to estimate the incidence rate of seizures among a large cohort of people with Alzheimer's. The researchers used anonymized electronic medical records from nearly 400 primary medical practices in the United Kingdom. The study population included 14,838 people with Alzheimer's aged 50 years or older and a comparison cohort of 14,838 randomly-selected, age- and sex-matched patients without Alzheimer's. People with Alzheimer's were followed for an average of 2.3 years; non-Alzheimer's patients were followed for an average of 3.4 years.
Over that time period, the researchers found that the rate of seizures, per 1,000 people per year, was 9.1 among patients with Alzheimer's disease compared with 1.4 for those without Alzheimer's – an incidence rate that was 6.4 times higher. In addition, they found that the incidence rate of seizures was highest among the youngest Alzheimer's patients, and that it decreased with age. Incidence among non-Alzheimer's patients increased slightly with age.
"The increased risk of seizures among patients with Alzheimer's disease was seen in all age groups, but there was a substantial increase among the youngest patients. It is especially important for these patients and their caregivers to be aware of this risk," Baker said.
"The connection between Alzheimer's and seizures provides additional avenues for research into the basic biology of both diseases, and possibly interventions and therapies to respond to the overall impact of Alzheimer's disease" Arrighi said.
Alzheimer's is Associated with Lower Hemoglobin Levels and Anemia
Studies suggest that iron accumulates in the tau tangles in the brains of people with Alzheimer's, and that overall levels of iron are elevated in both Alzheimer's and Mild Cognitive Impairment (MCI) brains. However, it is not clear from the scientific literature if this altered brain iron profile is reflected in plasma iron levels.
Noel Faux, PhD, of the Mental Health Research Institute, Parkville, Australia, and colleagues examined hemoglobin, iron and other blood-based measurements in the 1,112 participants (768 healthy controls, 133 MCI, 211 Alzheimer's) of the Australian Imaging Biomarkers and Lifestyle (AIBL) study of Ageing. Participants also completed questionnaires on diet and medication intake (including supplements). Results were then correlated with measures of short-term, long-term and total memory, and global cognition.
The researchers found that people with Alzheimer's in the study had significantly lower levels of hemoglobin, mean cell hemoglobin concentration (MCHC), and packed cell volume compared with healthy controls, after adjustment for age and gender. Consistent with these data, the erythrocyte sedimentation rate (ESR) was significantly higher in Alzheimer's compared to healthy controls.
Participants with anemia in the study were found to have an increased risk of Alzheimer's (odds ratio: 2.56). And people with Alzheimer's in the study were found to have an increased risk of being anemic (odds ratio: 2.61). Self reported iron intake was not different in the two groups.
"In our population, we found that people with Alzheimer's disease were more likely to be anemic, and this was not explained by dietary iron deficiency," Faux said. "This suggests that hemoglobin production is deficient in Alzheimer's patients."
"Alzheimer's had not previously been recognized as a risk factor for anemia, which is a common clinical problem for the elderly and can contribute to problems such as heart failure and renal failure," Faux continued. "The cause of anemia in Alzheimer's is still uncertain, but we speculate that Alzheimer's is a disease that affects both brain and blood. We are currently investigating this intriguing possibility."
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