Prevalence is 7.5 per cent in Chennai and 10.6 per cent in Vellore, TN

10/66 algorithm used can pick up milder dementia

Memory loss is considered normal sign of aging

Previous studies appear to have underestimated the prevalence of dementia in developing countries, India included. According to a paper published in the latest issue of Lancet, dementia can no longer be considered a problem predominantly seen in developed countries.

The prevalence in India, which was one of the seven low- and middle-income countries studied, has been found to be 7.5 per cent in the urban and 10.6 per cent in the rural population respectively.

The prevalence is arrived at by using a new 10/66 dementia algorithm that is meant for use in developing countries. It is sensitive enough to pick even the mild cases of dementia.

Earlier studies had found the prevalence to be in the range of 1.6 to 3.6 per cent. These studies had used the DSM IV dementia criteria (Diagnostic and Statistical Manual for mental disorders).

The study by the 10/66 Dementia Research Group, an international collaboration with Alzheimer’s Disease International and the Wellcome Trust, U.K., was undertaken in 1,000 individuals (men and women) aged 65 years and older in Chennai (urban setting), and a similar number in Vellore in Tamil Nadu representing the rural population.

The latest study now questions the accuracy of the results of a number of earlier studies.

“Our evidence suggests quite strongly that there is a problem with DSM IV criteria,” said Prof. Martin Prince to this Correspondent over phone from London. “There is a strong evidence of some degree of underestimation by previous studies.”

Prof. Prince is from the Institute of Psychiatry, King’s College London and is the Director of the 10/66 dementia research group.

With recent estimates suggesting that over 24 million people live with dementia worldwide, and 4.6 million new cases are added every year, the contribution by India can no longer be considered insignificant.

With longevity increasing in India, the number of people older than 65 is increasing. With it come the problems of old-age diseases. The huge population in India does not make things better either.

DSM IV is American-based criteria developed for clinical diagnosis of dementia. “DSM IV has very strict conditions; there should be impairments in memory and other aspects. And these impairments should be serious enough to affects day-to-day activities,” Prof. Prince explained.

Why underestimated

Using DSM IV criteria in the developing countries can lead to underestimation of prevalence due to several reasons.

“So what is relevant in one setting may not be applicable in another society. It is a disability weighted for dementia diagnosis,” said Dr. E.S. Krishnamoorthy, referring to DSM IV criteria. He is the Director of the Institute of Neurological Sciences at the Chennai based VHS. He is one of the authors of the Lancet paper. “The 10/66 algorithm does not place strong emphasis on disability.

Cognition tests

“So when we use this, we see a higher prevalence,” said Dr. Krishnamoorthy. “It is based on a set of cognitiontests .They are reasonably culturally and socially sensitive.”

The 10/66 algorithm, unlike its counterpart, can pick up milder forms of dementia.

In India, memory loss, which is one of the first signs of dementia, is often considered part of the normal aging process. This leads to relatives not considering it as very significant and failing to confirm the problem.

“In many parts of India, the awareness is low. And because of good family support, the mild symptoms are not noticed,” said Prof. Prince.

Mr. A.T. Jotheeswaran, Psychotherapist and Psychiatric Epidemiologist at the King’s College London is now conducting a follow up study of 1,000 people in Chennai to understand the progression of the disease and its incidence.