Many people who survive a heart attack may be at a higher risk for death, simply because they don't follow doctor's orders.

A new study from Canada finds about one-quarter of heart attack survivors don't fill their prescriptions to help prevent additional attacks.

Researchers say those who filled -none- of their prescriptions had an 80% higher chance of dying in the year following their heart attacks, compared with people who filled all of their prescriptions.

Whether it's because of finances, a lack of education about their follow-up treatment, or other reasons, researchers say it's unclear why some patients did not fill their prescriptions.

In other medical news…

Another study on heart patients indicates older Americans are being diagnosed earlier with heart failure, but appear to be living with the condition longer.

Researchers from duke university medical center analyzed files of more than 600,000 Medicare patients for the study.

While the rate of newly diagnosed heart failure cases fell among people aged 80 to 84, it rose among 65- to 69-year-olds.

The total number of Americans living with heart failure steadily increased over the 10-year study period.