Neurological disorders ranging from migraines to epilepsy and dementia affect up to one billion people worldwide and the toll will rise as populations age, the World Health Organization (WHO) warned.

The number of people suffering from Alzheimer and other debilitating dementias, currently some 24.3 million people, is expected to double every 20 years, with prevalence levels rising in developing countries, it said.

In a report entitled "Neurological Disorders: Public Health Challenges," the United Nations agency urged that neurological care become part of basic health care so that underdetected disabilities are diagnosed and treated, especially in Africa.

"Unless immediate action is taken globally, the neurological burden is expected to become an even more serious and unmanageable threat to public health," the WHO said.

Neurological disorders -- which also include strokes, multiple sclerosis, Parkinson's disease and brain injuries -- kill an estimated 6.8 million people each year, accounting for 12 percent of global deaths, it said.

"The burden of neurological disorders is reaching a significant proportion in countries with a growing percentage of the population over 65 years old," Nobel medicine laureate Rita Levi-Montalcini said in a foreword to the report.

Some cause paralysis, while others cause memory loss and other cognitive impairments, behavioral problems such as uncontrolled anger, or speech problems.

Yet weak health care systems, lack of trained personnel and essential drugs, and traditional beliefs which stigmatize many illnesses are deepening the treatment divide between rich and poorer nations, the WHO said.

Rehabilitation services are "limited or nonexistent in many developing countries" for people with disabilities attributable to neurological disorders, the report said.

Some 50 million people worldwide suffer from epilepsy, most of them in developing countries, but an "overwhelming majority" of patients don't receive drugs to halt the seizures, it said.

"Despite the fact that highly effective, low-cost treatments are available, as many as nine out of 10 people suffering from epilepsy in Africa go untreated," said WHO Director-General Margaret Chan.

Many people with neurological disabilities in poor communities depend totally on other people, usually family members, for help with daily life, according to the report.

"In some African countries, people believe that saliva can spread epilepsy or that the "epileptic spirit" can be transferred to anyone who witnesses a seizure. These misconceptions cause people to retreat in fear from someone having a seizure, leaving that person unprotected ...," it said.

Aspirin is the most cost-effective intervention for treating acute stroke and for preventing a recurrence, yet coverage with this inexpensive treatment is still "extremely low," it added.