NEUROLOGY India,
Some observations on the spectrum of dementia
Year : 2004 Volume : 52 Issue : 2 Page : 213-214
Diagnostic appraisal of dementia needs an optimistic approach for the benefit of the physician and the patient. With the advancement of new diagnostic tools it is easy to classify dementia into definite clinico-pathological groups. Epidemiological data about dementia appear conflicting as till the 80's MID was reported to be more prevalent than AD in Japan, Korea and China but in the 90's AD was documented as being twice as common as MID in these very countries.[3] AD has been consistently reported to be the commonest type of dementia by American and European studies.
We observed that AD, which is irreversible and common in the west, is uncommon in India. Similarly, prevalence of AD in Nigeria has also been observed as low.[3] Initially, it was attributed to poor suspicion, but in spite of adopting the NINCDS-ADRDA criteria,[2] we observed that about 75% patients in our study had a potentially treatable etiology or in whom progress of dementia could be halted. MID, infections, poorly distilled country-made liquor were other common yet treatable causes and so was nutritional dementia.
Most of the Indian studies have also reported MID to be more prevalent. In the first epidemiological study from the Indian subcontinent, the incidence of AD was reported to be amongst the lowest possible.[4] Explanations forwarded by the authors were short duration of follow-up, cultural factors and other potential confounders.
In a similar study in rural northern India an overall prevalence of AD has been described as very low (0.62% in the population over 55 years and 1.07% in those aged 65 and above). Of course this prevalence increased with age. Explanations postulated were low overall life expectancy, short survival with this disease and low age-specific incidence, potentially due to differences in the underlying distribution of risk and protective factors as compared with populations with higher prevalence.
[5]A community-based study in a rural population in Kerala reported 58% of patients with MID compared to 41% with AD. There were more women and positive family history was prominent in the AD group. Smoking and uncontrolled hypertension was associated with MID.
[6] A few Indian studies are also contradictory, with AD being suggested to be more prevalent than MID.[3] Interestingly, in another report from India the prevalence of dementia was observed to be higher in the rural population as compared to the urban settings.
[7]There is a difference in the incidence and prevalence of AD between underdeveloped and developed countries. Many interesting reasons have been cited. The widespread use of pesticides and the type of smoking has been directly correlated with MID, which is more prevalent in India. Another reason forwarded is the widespread use of electric lighting. Exposure to bright light suppresses the secretion of melatonin, a free radical scavenger, which inhibits progressive formation of beta sheets and beta amyloid fibrils. Its production is further reduced with aging, thus increasing susceptibility to age-related diseases like AD.[8]
Jha Sanjeev, Patel R
Department of Neurology, SGPGIMS, Lucknow, India.
Correspondence Address:
Associate Professor, Neurology Department, SGPGI, Lucknow,
Indiasjha@sgpgi.ac.in
link to the article :
http://www.neurologyindia.com/article.asp?issn=0028-3886;year=2004;volume=52;issue=2;spage=213;epage=214;aulast=Jha
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