Efforts to make hospitals safer for patients are falling short, researchers report in the first large study in a decade to analyze harm from medical care and to track it over time.

The study, conducted from 2002 to 2007 in 10 North Carolina hospitals, found that harm to patients was common and that the number of incidents did not decrease over time. The most common problems were complications from procedures or drugs and hospital-acquired infections.

“It is unlikely that other regions of the country have fared better,” said Dr. Christopher P. Landrigan, the lead author of the study and an assistant professor at Harvard Medical School. The study is being published on Thursday in The New England Journal of Medicine.

It is one of the most rigorous efforts to collect data about patient safety since a landmark report in 1999 found that medical mistakes caused as many as 98,000 deaths and more than one million injuries a year in the United States. That report, by the Institute of Medicine, an independent group that advises the government on health matters, led to a national movement to reduce errors and make hospital stays less hazardous to patients’ health.