COPENHAGEN – Researchers appear to be tracking contradictory trends in the global incidence and prevalence of Alzheimer’s disease.
There’s no doubt that both are declining in the United States and other high-income countries. But the disease appears to be claiming more people in less-developed countries, particularly in Asia and sub-Saharan Africa, and that disparity will become much worse by 2050.
Dr. Martin Prince
Half of the 7.7 million new cases diagnosed per year are occurring in China alone, Dr. Martin Prince said at the Alzheimer’s Association International Conference 2014. And while African and Latin American countries contribute a lower portion of the total (7% and 5%, respectively), they are projected to proportionally outstrip even China’s expected tripling of cases, with each poised for a fourfold increase by 2050.
Taken together with the doubling of cases expected in the United States and European countries, the global incidence could exceed previous projections by more than 30 million cases worldwide by 2050, said Dr. Prince, a primary author of the G8 report "The Global Impact of Dementia, 2013-2050." The report contains updated numbers based on data supplied by the United Nations.
"Because of this new U.N. data, and new data coming out of China, we realized that our 2009 global estimates were about 10% too low," said Dr. Prince, who is also a professor of epidemiological psychiatry in the Institute of Psychiatry at King’s College London. "We are talking about not 36 million right now, but 44 million. Not 66 million by 2030, but 76 million. And by 2050, not 115 million as we previously thought, but 135 million."
The upward trend doesn’t reflect so much an increase in disease incidence as an increase in disease reporting, he noted. While China has published papers on incidence and prevalence, they were almost exclusively in Chinese journals and unavailable outside the country. The biggest change came from a groundbreaking paper in 2013 (Lancet 2013;381:2016-23) – the first widely accessible English language paper on the topic. It concluded that the burden of dementia in China is increasing faster than previously assumed.
According to the G8 report, about 67 million are living with Alzheimer’s in China now, and that number could increase to nearly 200 million by 2050.
But that paper probably doesn’t tell the whole story, Dr. Prince added. China is suffering from the same epidemics of obesity and diabetes that plague other countries, and in contrast to many, cigarette smoking is on a huge rise in China. All of these factors contribute to the development of Alzheimer’s and other dementias, so the numbers will most likely continue to change.
Perhaps not surprisingly, national prosperity is directly tied to Alzheimer’s incidence. By 2050, the incidence is projected to increase by 106% in the G8 countries and by 185% in the G20 countries. This is mainly due to higher educational levels and better risk management, Dr. Prince said. Reducing the prevalence of diabetes, physical inactivity, smoking, depression, low education, and midlife hypertension and obesity could reduce the Alzheimer’s population-attributable risk fraction by more than 50%.
"Even a 10% reduction in risk exposure would result in 250,000 fewer new cases [3.3%]. A 25% reduction in risk exposure would result in 680,000 fewer new cases," an incidence reduction of almost 9% worldwide, he said.
No one has yet modeled the global economic impact of the rising Alzheimer’s tide, Dr. Prince said. Current worldwide spending on Alzheimer’s disease exceeds $600 billion per year. In developed countries, most of this is associated with care in long-term facilities and the cost of professional caregivers. "In less-developed countries, the largest proportion is the informal costs of family care, especially lost employment opportunities. This needs to be calculated, and I’m not aware that’s being done. But it will be a lot of money."
Dr. Prince had no financial disclosures.
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