根据短文内容从下框的6个选项中选出能概括每段主题的最佳选项，其中有一项是多余。
| A． what is dementia? B．A new opinion on the cause of disability C．A study on disability problems of children D．What should the World Health Organization do to solve the problem? E．A study on disability problems of the elderly F．More attention should be paid to old people’s brain and mind diseases． |
1．__________
The World Health Organization（WHO）says that blindness and other visual problems are the leading causes of disability of older people in low-and middle-income countries．However， some researchers disagree with WHO on this point．They made a study and found that the leading cause is dementia（痴呆）．
2．
Dementia is a loss of intellectual ability that affects memorizing，learning and thinking abilities and other language skills．People with dementia may forget family members or not know what day it is．Sometimes they become angry or sad，and they can often hear voices，or see things that are actually not there．
3．
Renate Sousa from the Institute of Psychiatry at King’s College London and other researchers made a new study．The study dealt with the causes of disability among fifteen thousand people aged over sixty-five in seven countries，which include China，India，Cuba，the Dominican Republic，Venezuela，Mexico and Peru．The team found that dementia was the leading cause of disability of the elderly in areas except rural India and Venezuela．Other major causes were stroke， arthritis（关节炎），depression， visual problems and gastrointestinal（胃肠道的） problems．
4．
In low-and middle-income countries，heart diseases and cancer get more attention than chronic（慢性的）diseases．However，researchers say that great importance should be given to chronic diseases of the brain and mind．As the population ages， the society will have to deal with more and more cases of dementia．The study shows that the elderly is nine percent of the total population in low-and middle-income countries today．However，the number is growing quickly．It is likely to reach twenty percent of the total population by the middle of the century．
5．
An article published in the Lancet medical journal dealt with a special issue on disability．It was a study on disability and children in eighteen low-and middle-income countries．It indicated that in almost half of the countries， children who were breast-fed were less likely to have a disability than those who were not．The same was true of those who had a deficiency of vitamin A and those who were underweight．Children who did not take part in early learning activities or attend school were also more likely to be disabled than those who did．