US dementia rates on the decline, new study suggests

The percentage of older Americans that have Alzheimer’s disease or other forms of dementia has dropped by almost one-fourth, from 11.6% in 2000 to 8.8% as of 2012, according to a new study published online Monday by the peer-reviewed medical journal JAMA Internal Medicine.

That’s a drastic reversal from previous research, which claimed that aging baby boomers would cause the number of Alzheimer’s patients to triple by the year 2050, according to health, science and medical news website Stat. The statistics suggest that something is responsible for this shift, and that by pinpointing that cause, doctors may be able to further reduce dementia rates.

As part of their research, Dr. Kenneth Langa from the University of Michigan and his colleagues reviewed the records of 21,000 people with an average age of 75. They found that fewer of those individuals had dementia than in the past, based on their performance on standardized tests, NBC News and the New York Times explained.

Furthermore, they found that the condition was not being diagnosed as early as it previously had been. In 2000, the average age at which patients received a dementia diagnosis was 80.7. In 2012 the average age of 82.4, the study authors said. One factor that Dr. Langa’s team credits for these findings is an increase in education level among US adults during the past 25 years – in fact, they noted, the average education level increased from 11.8 years in 2000 to 12.7 in 2012.

The research, the study authors explained, “supports the notion that ‘cognitive reserve’ resulting from early life and lifelong education and cognitive stimulation may be a potent strategy for the primary prevention of dementia in both high- and low-income countries around the world.”

Education, weight may help explain surprising results

Education can produce greater cognitive reserve, which according to Stat means that individuals have built up enough back-up neurons and synapses that losing some due to Alzheimer’s disease does not necessarily mean that they will wind up having full-blown dementia. However, this alone was not sufficient to explain the findings – other factors were involved, they said.

Oddly enough, while obesity, poor eating habits, and a sedentary lifestyle have all been found to increase a person’s risk of Alzheimer’s, these conditions were found to be associated with lower risk of dementia, Dr. Langa and his colleagues found. In fact, NBC News noted that patients who were heavier, had high-blood pressure, or were diabetic tended to have lower dementia rates.

Specifically, the Times said, overweight and obese people had a 30% lower risk of dementia than normal weight people, while those who were underweight faced a risk that was times 2.5 greater. In a commentary accompanying the new study, Ozioma C. Okonkwo and Dr. Sanjay Asthana of the University of Wisconsin’s School of Medicine and Public Health wrote that “late-life obesity may be protective” in terms of dementia risk, even though past studies suggested otherwise.

Rush University Medical Center professor Dr. Denis Evans told the Times that people should be cautious in both accepting that dementia rates were on the decline, and that education and weight may be possible reasons for the trend. However, as Stat pointed out, the new study is supported by statistics published earlier this year which found that dementia risk among older patients had decreased by about 20% every decade from 1977 through 2008.


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