Up to 70 percent of hysterectomies in the United States, a quarter of knee replacements in Spain and more than half the antibiotics prescribed in China are inappropriate, overused healthcare, researchers said on Monday.

Experts who carried out a series of studies across the world found that medicine and healthcare are routinely both over- and underused, causing avoidable harm and suffering and wasting precious resources.

The studies, commissioned by The Lancet journal and conducted by 27 international specialists, also found rates of Caesarian section deliveries are soaring - often in women who do not need them - while the simple use of steroids to prevent premature births has lagged for 40 years.

"A common tragedy in both wealthy and poor countries is the use of expensive and sometimes ineffective technology while low-cost effective interventions are neglected," the experts wrote in a statement about their findings.

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The World Health Organization estimates that 6.2 million excess C-sections are performed each year - 50 percent of them in Brazil and China alone.

Vikas Saini, one of the lead authors of the study series and president of the U.S. Lown Institute in Boston, said factors driving the global failure to the right level of care include "greed, competing interests and poor information", which he said combine to create "an ecosystem of poor healthcare delivery."

Co-lead researcher Shannon Brownlee added: "Patients and citizens need to understand what's at stake here if their health systems fail to address these twin problems. In the U.S., we are wasting billions of dollars that should be devoted to improving the nation's health."

The study series analyzed the scope, causes and consequences of underuse and overuse of healthcare around the world. It found that both can occur in the same country, the same organization or health facility, and even afflict the same patient.

The researchers noted that a study in China found 57 percent of patients received inappropriate antibiotics; that inappropriate hysterectomies in the United States range from 16 to 70 percent; and inappropriate total knee replacement rates were 26 percent in Spain and 34 percent in the United States.

Rates of inappropriate hysterectomies were 20 percent in Taiwan and 13 percent in Switzerland, they found.

Underuse leaves patients "vulnerable to avoidable disease and suffering" the researchers said, while overuse causes avoidable harms from tests or treatments at the same time as wasting resources better spent on much-needed services.