More than 2 million people die every year and every death certificate includes what killed them.

But NewsChannel5 and Scripps Howard News Service reviewed nearly 5 million death records in Ohio and across the country.

The 5 On Your Side investigation found, in many cases, the cause of death is nothing more than a good guess.

"Coronary heart disease is probably the most common cause of death. And so when it comes to a situation where a physician is unsure, that's sort of the default diagnosis," Robert Anderson of the National Center for Health Statistics said.

Medical experts believe roughly 20 percent of deaths are caused by heart disease. But in Ohio, heart disease rates jump to nearly 30 percent in some counties:

• Cuyahoga County: 28.5 percent
• Ashtabula County: 28.2 percent
• Lake County: 26.8 percent

But without an autopsy, it's often just a guess.

Anderson said, "They will tend to just say coronary heart disease, heart disease, without specifying whether it's coronary or not."

And nationwide, who signs the death certificate varies widely. In Ohio, coroners are required to be physicians.

But Cuyahoga coroner Dr. Frank Miller said that's not true everywhere.

"In many states, the coroner, or in the case of Texas, the justice of the peace, doesn't have to have any medical training or legal training, but they are responsible for assigning causes of death," Miller said.

In Ohio, 8.4 percent of deaths undergo autopsies. The highest rate is in Colorado, where more than 12 percent of deaths undergo autopsies.

Veteran coroner Dr. Michael Doberson said there is a nationwide problem.

"Right now our coroner and medical examiner system, our death investigation system, is really a patchwork of different systems. And with that patchwork goes varying degrees of thoroughness with respect to carrying out autopsies and death investigations," Doberson explained.

Why does it matter? Because without an accurate death certificate, you may never know of a serious disease that runs in your family and your tax dollars can be wasted on medical research.

"So if the death certificate statistics are skewed by inaccurate opinions, essentially you may fund a disease that really is overrepresented on the death certificates and underrepresented in the population," Miller said.

In some cities around the country, fatal heart disease rates are three times higher than others -- not because of real heart problems, but because death certificates that are wrong.

More Information:
What's Really Killing America?
Who Gets Autopsied?