Are 18 year old and 44 year old hearts the same? Why did they include such a wide demographic to create their calculations? Would they have the same results if it were 18-21 year olds? 21-30 year olds? 30-40 year olds? Nonetheless, according to their numbers – these elements are not important. The 18-year-old heart and the 44-year-old-heart is exactly the same and once they have eliminated all other comorbidities, they came to this conclusion.