The Growing Global Burden of Neurologic Disease

WASHINGTON, DC —Changing demographics in the world’s most populous countries in the next few decades will result in a significant increase in the number of persons with neurodegenerative diseases, including dementia and Parkinson’s disease. That was the news presented by Ray Dorsey, MD, MBA, at the 132nd Annual Meeting of the American Neurological Association.

“The current burden of neurologic disease is already high,” said Dr. Dorsey, an Assistant Professor of Neurology at the University of Rochester, New York. According to figures from the World Health Organization, neurologic and neuropsychiatric diseases account for 16% of the total disease burden throughout the world. “The future burden will grow even higher,” Dr. Dorsey projected.

LONGER LIFE EXPECTENCY, CHANGING POPULATIONS

Two main factors are accountable for this anticipated growth, according to Dr. Dorsey. The first stems from the dramatic increase in life expectancy throughout most of the world. During the past 50 years, life expectancy has increased by 10 to 20 years in all parts of the world, with the exception of sub-Saharan Africa.

The second factor, a consequence of the first, is the change in population structures, especially in the most populous countries. Demographers depict population structures as population pyramids, which are stacks of horizontal bars representing an age-group (eg, people from birth to age 4 up to those older than 100). The width of each bar represents the number of people of that age. In some countries, such as India, the population structure is pyramidal in shape, broad at the bottom and tapering sharply to become very narrow at the top, reflecting the large number of young people and relatively few older ones. In the United States, and especially in many countries in Europe, the structure tapers far less sharply, due to the relatively larger proportion of elderly persons. “In 25 years, the US population structure will mature even further, so that the number of people between zero and age 70 in each of the age ranges will be about the same,” Dr. Dorsey said. Within the same time frame, India’s structure will more closely resemble that of the US today. There will be a large growth in the number of middle-aged individuals, and the number of people older than 60 will double.

“These two changes will lead to a growth in the number of individuals throughout the world with neurodegenerative conditions,” said Dr. Dorsey. The number of people with Parkinson’s disease, for instance, will grow modestly in Europe, somewhat more in the US, and quite significantly in Southeast Asia. “This growth will be especially significant in China.

“We conservatively estimated the number of individuals with Parkinson’s disease in the world’s most populous countries was 4.1 million in 2005. We project that number will more than double by 2030. By that time, over half the people with Parkinson’s disease in the world’s most populous countries will be Chinese.”

Even more substantial changes are expected for dementia, which affects approximately 25 million people worldwide. By 2040, that number is expected to increase to 80 million, also driven by population changes in developing countries.

The consequences of a greater burden of neurologic disease will be large, Dr. Dorsey believes. “Most of the attention to health in the developing world is devoted to acute, often infectious conditions,” he said. “But the growing burden of neurologic illness will have profound social implications.

“Unfortunately, many of the countries that will experience this growth are ill-equipped to handle even their present burden,” Dr. Dorsey pointed out. In China, for example, access to health care is largely restricted to those who are able to pay for it. In Bolivia, no persons with Parkinson’s disease identified in a recent health survey had ever been diagnosed by a physician prior to the study.

According to a 2005 study in the New England Journal of Medicine, the mortality rate from stroke in China among those ages 40 to 64 is seven times that in the US. This will have an effect on productivity, but more importantly, it will have a heavy impact on families and communities, as they attempt to cope with lost income and an increased burden of care for relatives with chronic conditions, noted Dr. Dorsey. An increase in the number of people with these conditions will place more demands on scarce public resources.

One potentially mitigating factor for this outlook is development, Dr. Dorsey suggested. As countries develop and obtain more resources, they usually devote more funding to health care. Wealthier nations spend almost two times more per capita of their gross domestic product (GDP) on health care than do poorer countries; the US spends three times as much.

China has made changes in its health care spending in the past two decades. In 1990, its per capita GDP was $2,000, of which 2% was devoted to health care. By 2003, China’s GDP had increased to $6,000 per person, of which 6% was spent on health care, a ninefold increase in a little more than a decade. The actual amount spent per person in 2003 was only $250. “Even this degree of growth will be insufficient to address the burden that these countries will face,” Dr. Dorsey said.

What will be needed, he said, are creative solutions, such as one implied in the recent announcement by the Chinese government that it will reinstitute its rural health program, which is especially important because only a very small proportion of the rural population has health insurance. Enlightened self-interest on the part of industries is also likely to be part of the solution, Dr. Dorsey added. He noted that a South African gold-mining company has recently begun to offer retroviral therapy to its employees, after finding that HIV infection among its workers cost $5 for every ounce of gold that it produced. “It made financial sense to this company,” he said.

“To address the growing burden of neurologic disease, we will need more creative solutions like these, including contributions from neurologists,”
Dr. Dorsey concluded.            

NR