Dementia is the loss of mental abilitiescaused by brain disorders that affect memory,thinking, behavior and judgment.The most common cause of dementia,especially in older people,is Alzheimer's disease.It causes up to seventy percent of dementia cases.Worldwide an estimated thirty-six million peopleare living with dementia.A new report predicts that number will increase to more than one hundred fifteen million by twenty-fifty.The report is from the World Health Organizationand Alzheimer's Disease International.Marc Wortman is the executive director of this groupof seventy-eight Alzheimer's associations.MARC WORTMANN: "There is a new case nowin every four seconds, a new case of dementia in the world.Only ten years ago, it was calculatedat one in seven seconds, so it is speeding up.And if you look into the future projections,it may be close to one in every secondby the year twenty-fifty.So we need to act.We need to do something to stop this epidemic."The number of cases in the heavily populateddeveloping world is expected to growas more people live longer.The report says more than half of those with dementianow live in low- and middle-income countries.This number is likely to rise to more than seventy percent by twenty-fifty.People are living longer because ofbetter health care and increasing wealth.But the report says dementiais not a normal part of growing old.Shekhar Saxena is the director of mental healthand substance abuse research at the WHO.SHEKHAR SAXENA: "Dementia is often not recognized.It is commonly mistakenfor an age-related decline in functioningbecause it can mimic age-related problems,and also it progresses slowly.Even in high-income countries,only one-fifth to one-half of the cases of dementiaare routinely recognized.This percentage is obviously much lowerin middle and low-income countries."Martin Prince is a professor at Kings College London.He says many people wrongly believethat dementia and Alzheimer's diseaseare not problems in poorer countries.MARTIN PRINCE: "There have been some more studies donerecently in western Africa, which, I think give the lieto the notion that Alzheimer's diseaseis very rare amongst all the people in Africa.There are fewer older people because life expectancy is shorter,particularly with the ravages of HIV.But, amongst people who live into old age,the prevalence of dementialooks quite similar to high-income countries."The world currently spends more thansix hundred billion dollars a yearto treat and care for people with dementia.Yet the WHO says only eight countries currentlyhave national programs in place to deal with dementia.It urges greater efforts to identify dementia early,educate the public and provide better care.Dementia may be incurable, but health officials saymuch can be done to improve the lives of people who have it,and support their families and caregivers.And that's the VOA Special English Health Report.