Today is World Alzheimer's Day. The day is meant to spread awareness about Alzheimer's disease across the world. Doctors say, with an increasing elderly population falling prey to it, Alzheimer's disease, a kind of dementia, stands as one of the biggest health threats in India. The disease, caused by the degeneration of brain cells and nerves, impacts functioning of the brain, effecting day-to-day activities by its victims. Though the causes of the disease are not completely known yet, India has almost a fourth of the world's Alzheimer's patients.