Almost 25% of patients experienced at least one adverse event while in the hospital, according to a new study published in the New England Journal of Medicine—underscoring the continuing need to improve patient safety.

Study details and key findings

Adverse events are a significant problem in hospitals. In 1991, the landmark Harvard Medical Practice Study (HMPS) found that there were 3.7 events per 100 admissions. Of these events, 28% were considered preventable.

In the current study, researchers analyzed data from 2,809 patients collected from 11 Boston-area hospitals, which ranged in size from fewer than 100 beds to more than 700, in 2018. Patients who were at the hospital for hospice, rehabilitation, addiction treatment, psychiatric care, or observation only were excluded from the study.

To identify potential adverse events, a panel of nine nurses reviewed admissions records. According to the study, an adverse event was defined as "unintended physical injury resulting from or contributed to by medical care that requires additional monitoring, treatment, or hospitalization, or that results in death."

This data was then reviewed by eight physicians to determine the type of adverse event. Each event was also ranked on a severity scale of significant, serious, life-threatening, or fatal.

Overall, 663 or 23.6% of all patients experienced at least one adverse event. Among all admissions, 523 had at least one significant adverse event, 211 had a serious adverse event, 34 had a life-threatening adverse event, and 7 had a fatal adverse event.

Of the 978 total adverse events that were identified, 222 were determined to have been preventable, and 316 had a severity rating of serious or higher. The most common types of adverse events were adverse drug events (39%), surgical or other procedural events (30.4%), patient-care events (15%), and healthcare-associated infections (11.9%).

In general, adverse events were more likely to occur in older patients and among men. They were less frequent among Asian and Hispanic patients compared to Black or white patients, as well as among patients with Medicaid as their primary insurance.

"Three decades after the HMPS drew attention to the issue of healthcare-associated patient harm, in-hospital adverse events continue to be common," the researchers wrote. "… Our findings are an urgent reminder to all health care professionals of the need for continuing improvement in the safety of the care we deliver."

'Disappointing, but not shocking'

According to David Bates, the study's lead author, as well as chief of general medicine at Brigham and Women's Hospital and medical director of clinical and quality analysis at Mass General Brigham, the study's findings are "disappointing, but not shocking."

"It's clear that, at least, the rate is not going down and that harm continues to be a really serious issue," Bates said.

Albert Wu, director of the Center for Health Services and Research Outcomes at the Johns Hopkins Bloomberg School of Public Health, noted that while progress has been made in some areas of patient safety, new risks have emerged as medicine has evolved over time.

"Although we have eliminated some causes of harm, there are new kinds of harm that have been created, associated with potent new medications and new procedures," Wu said.

For example, drug companies have made significant advances over the last few decades, but with a proliferation of new drugs also comes more opportunities for medication-related errors.

"There are many more medications available today compared to 1991, and some of the medicines have a smaller therapeutic margin, which is the gap between the therapeutic effect and dangerous dose," said Donald Berwick, the president emeritus and a senior fellow at the Institute for Healthcare Improvement.

"New technologies are always double-edged and you need to have intense surveillance to monitor them," Berwick added. "You need to anticipate what can go wrong and build dykes around the hazards."

Linda Aiken, a professor and the founding director of the Center for Health Outcomes and Policy Research at Penn Nursing, believes the main cause of patient safety issues is in adequate staffing.

"Since we've been doing research on patient safety, we consistently find that one of the major explanations for poor patient outcomes is insufficient numbers of nurses at the bedside," Aiken said.
"Having a sufficient number of nurses is a building block for safety."

Currently, only one U.S. state, California, has minimum staffing requirements in hospitals to ensure safety. In California, one nurse can care for only up to five patients at a time.

"If you actually implemented a standard like this, you could save a lot of lives that fall under patient safety," Aiken said. "These are preventable, but there are too few nurses there to provide the type of care that would prevent those adverse events from happening."

Wu encouraged patients to be more active in their own care by telling hospital workers about their diagnoses, medications, allergies, and care that they've received elsewhere.

"If you think something might be wrong, speak up!" Wu said. (Sullivan, NBC News, 1/11; Lagasse, Healthcare Finance, 1/19; Splete, Medscape, 1/18; Muoio, Fierce Healthcare, 1/19; Bates et al., New England Journal of Medicine, 1/12)