Alzheimer's Deaths May Rival Cancer Study says it's under-reported, is actually No. 3 cause of death By John Johnson, Newser Staff Posted Mar 5, 2014 7:25 PM CST 3 comments Comments (Shutterstock) (Newser) – The official stats on Alzheimer's have it as the sixth-leading cause of death in America, with about 83,000 fatalities a year. But new research suggests that undershoots the mark six-fold, reports CNN. The study in Neurology estimates that Alzheimer's kills 503,000 people a year, a number that would make it the No. 3 cause of death behind heart disease (600,000) and cancer (575,000). Researchers led by an epidemiologist at the Rush Alzheimer's Disease Center in Chicago say that death certificates under-report Alzheimer's by attributing the death to a more immediate problem such as pneumonia. “Death certificates may not be the best way to measure how many people die from something that takes up to 10 years” to reach its full effects, lead author Bryan James tells the Washington Post. "We’re not saying they didn’t die of those things; we’re just saying, ‘Well, what put them in the hospital with that condition?'" The researchers got their 503,000 figure by extrapolating from an eight-year study of 2,500 people age 65 and older who agreed to be tested for dementia and to donate their brains at death, reports NBC News. The scientists say it should be a wake-up call given that the number of Alzheimer's cases is projected to triple from 5 million by 2050 as the Boomers age.