A random sample survey for prevalence of major neurological disorders in Kolkata

Large scale epidemiological studies on neurological disorders are very few in India. We therefore planned to conduct a cross-sectional population-based epidemiological study on a stratified randomly selected sample from the city of Kolkata to study the prevalence of major neurological disorders such as epilepsy, stroke, dementia and Parkinsonism.

The method of case ascertainment was two- stage house-to-house survey; the first stage was undertaken by a field team consisting of four field workers and a neuropsychologist. Screening questionnaire based on National Institute of Mental Health and Neuro Sciences (NIMHANS) protocol was used. In the second stage a neurologist examined all the screened positive cases.

A total of 52,377 subjects participated in the study. The crude prevalence rates (per 100,000 population) of major neurological disorders with 95 per cent confidence intervals (95% CI) and age adjusted rates (AAR) based on US 2000 population were 557.5 (95% CI 496.17-624.40 and AAR - 516.77) in epilepsy, 486.85 (95% CI 377.0 to 551.11 and AAR-765.68) in stroke, 87.82 (95% CI 64.02-117.50 and AAR-168.4) in dementia and 45.82 (95% CI 29.64-67.63 and AAR-71.64) in Parkinsonism. The weighted prevalence rates (per 100,000) of the whole population based on re-screening of 10 per cent of negative samples were 763.89 (95% CI 690.55- 842.57) in epilepsy, 624.32 (95% CI 555.64-699.24) in stroke and 139.37 (95% CI 108.71-176.06) in dementia.

A high rate of stroke and overall lower prevalence of Parkinsonism and dementia was recorded as compared to western studies. High prevalence rate of stroke emphasizes the need to study incidence, morbidity and mortality profile of stroke including its socio-economic impact and also case-control analysis to determine the underlying risk factors.