Researchers from King's College London have led a new study that has shown that cases of dementia in the developing world are far more prevalent than previously thought.
Recent estimates have shown that over 24 million people live with dementia worldwide, with 4.6 million new cases every year.
However, a number of studies have suggested that the prevalence of dementia in the developing world is between a quarter and a fifth of that typically recorded in developed countries.
Now, the new study has cast a doubt on these results.
Professor Martin Prince from the Institute of Psychiatry, King's College London, who leads the research team, believes that a number of factors might have led to researchers underestimating dementia in the developing world.
"It's likely that cultural differences may be partly responsible for researchers missing cases of dementia," The Lancet quoted Professor Prince, as saying.
"Our evidence suggests that relatives in developing world countries are less likely to perceive or report that their elders are experiencing difficulties, even in the presence of clear evidence of disability and memory impairment," he added.
For the study, researchers assessed almost 15,000 people over the age of 65 in eleven countries, including India, China, Cuba and Peru.
The assessment consisted of interviews with the participant and, typically, a family member, as well as a physical examination and a blood test.
According to the study, prevalence of dementia in urban settings in Latin America is comparable with rates in Europe and the US, though the prevalence in China and India is lower.
Dementia leads to associate disability, such as memory impairment, affecting the quality of life of the patient.
However, pilot studies conducted by the group suggested that dementia also places a high burden on the carer and that this is exacerbated by lack of knowledge of the disease and its likely progression.
"You could question the point of labelling someone as having dementia if their relatives do not acknowledge it as a problem," Prince said.
"Our data suggest that even if it is not recognised as dementia, the illness places a heavy burden on both the elderly patient and their relatives. Being able to estimate accurately the true population of people living with burden is the first important step towards putting into place appropriate health and social care systems," he added.
According to the researchers, the findings will enable policymakers in low-income and middle-income countries to prioritise more effectively, as they begin to invest more heavily in the prevention and control of chronic non-communicable diseases.
The study was presented at the International Conference on Alzheimer's Disease and published online today in the journal The Lancet.