Five of the six top causes of death in America — including stroke, cancer and diabetes — now have lower death rates than they have in past years, according to a new report.

To investigate the deadliest conditions in the United States, researchers pulled national mortality data from death certificates, looking at the period from 1969 to 2013. They found that the yearly death rate for all causes for people younger than 75 fell by 43 percent.

In 1969, there were 1,278 deaths per 100,000 people under age 75 in the U.S. In 2013, that number had dropped to 730 deaths per 100,000 people younger than 75.

Deaths from stroke had the most substantial decrease, falling 77 percent (from 156 deaths per 100,000 people to 36 deaths per 100,000 people) during the study period, and heart disease was close behind, down by about two-thirds (from 520 deaths per 100,000 people to 169 deaths per 100,000 people), the researchers found. [9 Healthy Habits You Can Do in 1 Minute (Or Less)]

The researchers noted three likely reasons why the death rates from heart disease and stroke dropped: There are now better ways to treat high blood pressure and high levels of bad cholesterol (both of which are linked to heart disease and stroke), the smoking rate is lower (smoking is also linked to these conditions) and medical care has generally improved.

However, although the death rates from heart disease, stroke and diabetes have dropped in recent years, those decreases are now slowing down, the researchers said.

The death rates from unintentional injuries dropped by 40 percent during the study period (from 65 deaths per 100,000 people to 39 deaths per 100,000 people per year). The cancer death rate dropped by 18 percent (from 198 deaths per 100,000 people to 163 deaths per 100,000 people per year); and the diabetes death rate dropped by about 16 percent (from 25 deaths per 100,000 people to 21 deaths per 100,000 people per year), according to the report, published online today (Oct. 27) in the journal JAMA.

"The reduction in cancer deaths since the early 1990s is also an outcome of tobacco control efforts, as well as advances in early detection and treatment," the researchers said in the report.

The decrease in the death rate from unintentional injuries is likely due to declines in vehicle-related deaths, they said.

However, the death rate from chronic obstructive pulmonary disease doubled over the study period, from 21 deaths per 100,000 people in 1969 to 42 deaths per 100,000 people in 2013, the researchers found. This increase might be a result of obesity, as well as continued smoking, lead author Jiemin Ma, a researcher at the American Cancer Society, and colleagues, said in the report.

Higher obesity rates may also explain the leveling in death rates from diabetes among adults, the researchers added.

In an editorial published today in JAMA alongside the study, Dr. James McGinnis, an epidemiologist at the National Academy of Medicine in Washington, D.C., said the report "offers valuable insights on the trends over nearly half a century in deaths from all causes."

However, although the new report didn't mention Alzheimer's disease or suicide — or racial inequalities in death rates — these areas should remain high priorities for health care research, he said.

Alzheimer's disease moved from the eighth-leading cause of death in 2000 to the sixth-leading cause in 2013, McGinnis wrote in the editorial.

Suicide rates also increased by one-third from 2000 to 2013, "highlighting the importance of mental health and depression as prominent health challenges," McGinnis said.

What's more, death rates among black people were about double those for white people in infant mortality, heart disease, diabetes and prostate cancer in 2013, he said.

"Ultimately, the most fundamental national challenge is bringing the best health possible to its entire population, regardless of race, ethnicity and socioeconomic status," McGinnis wrote in the editorial.

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