We looked at what conditions receive the most research funding compared with the leading causes of death in the US. Here's what we learned from 2021.

• Heart disease, cancer, COVID-19, unintentional injuries, and strokes claimed the most lives in 2020.
• The conditions that caused the most deaths and the best-funded conditions often don't align.

The diseases that kill the most people don't always match up with the diseases that receive the most funding.

Insider looked at provisional data from the Centers for Disease Control and Prevention's National Vital Statistics System on the leading causes of death in 2020, the most recent year for which any comprehensive data is available, as well as 2021 research-funding estimates from the National Institutes of Health. The funding numbers include the value of all grants, contracts and other ways the NIH used to fund research.

The most common causes of death in the US in 2020 were heart disease, cancer, COVID-19, unintentional injuries, and strokes, while the areas with the most NIH funding were cancer, Alzheimer's disease, COVID-19, chronic lower respiratory diseases, and heart disease.

The diseases with the biggest discrepancy between deaths and funding are heart disease, strokes, and suicide, with about 445, 350, and 301 deaths per million dollars spent.

Some of the discrepancies between the biggest killers and the most-funded diseases might be due to stagnation in progress, as is likely the case for the relative lack of heart-disease funding. On the other hand, a disease like Alzheimer's might receive more funding because many people with the condition will die from other immediate causes; thus, coroners often don't list Alzheimer's as a cause of death.

US causes of death have remained largely consistent year to year, until COVID-19 joined the list in 2020.

As of Saturday, about 797,000 people have died from COVID-19. 2021 is the first year for which the NIH reported coronavirus research funding, much of which came from a 2020 stimulus package.