The drug and device industry now funds six times more clinical trials than the federal government, according to Johns Hopkins University researchers.
That means companies with financial interests in the studies now have more control over what doctors and patients learn about new treatments.
Clinical trials test new therapies on humans for safety and effectiveness before they are approved for wide use.
While the companies are expected to pay for trials of their products, studies exclusively funded by them can be narrow or even biased, said Dr. Stephan Ehrhardt, the Johns Hopkins study leader. This was less of a concern in the past because industry-funded research wasn't the dominant source of information. It's a different story today.
"When looking at the numbers, I see an imbalance," said Ehrhardt, an associate professor in the Bloomberg School of Public Health's Department of Epidemiology. "Industry doesn't fund trials most important for public health because they have no incentive to do that."
The trend emerged as the budget for the National Institutes of Health — the primary source of government funding for clinical trials — has been slashed 14 percent since 2006 amid belt-tightening in Washington.
The funding pinch has been acutely felt at Johns Hopkins, which receives the largest share of NIH money of all academic institutions.
Mark Grayson, a spokesman for the Pharmaceutical Research and Manufacturers of America, or PhRMA, which represents the country's large biopharmaceutical researchers and biotechnology companies, said companies are not only finding important new therapies but adhering to voluntary principles that outline ethics and sharing of clinical information.
"Pharmaceutical companies are committed to conducting rigorous clinical trials and communicating those results," said Grayson. "Clinical trials are important to determining the efficacy and safety of the medicines patients need."
A spokesman for the Medical Device Manufacturers Association didn't respond to a request for comment.
Dr. Reshma Jagsi, the deputy chair of the University of Michigan's department of radiation oncology, who has studied clinical trial funding and outcomes, said the Johns Hopkins study continues to document "a quiet but critical shift in the funding for clinical trial — the evidence upon which we base changes in medical practice."
Jagsi, who was not involved in the Hopkins study, said shrinking federal funding has made industry an important source of research. But, she added, "Conflicts of interest can also have a pervasive influence on the research questions that are asked, the ways that studies are designed, the framing of the analyses and results, and the decision to disseminate the findings."
"We cannot afford to rely too heavily on industry; biomedical research has critical benefits for both population health and economic prosperity, meriting robust public funding," Jagsi said.
The radiation oncologist was author of a study in 2009 that found industry funding may have skewed clinical trial outcomes. The university's Comprehensive Cancer Center found conflicts of interest in more than one-third of 1,500 cancer studies published in prominent medical journals in 2006.
Those trials were more likely to produce positive findings about the drug or device being studied. The university considered conflicts to include industry funding and company employees performing the research.
In the Johns Hopkins study, published Tuesday in the Journal of the American Medical Association, Ehrhardt found that the number of clinical trials funded by companies increased 43 percent from 2006 to 2014, while the number of NIH-funded trials decreased 24 percent over the same period.
By 2014, 6,550 clinical trials were funded by industry and 1,048 by the NIH.
The study tracked clinical trials listed in the government database, clinicaltrials.gov, the largest online registry.
Ehrhardt said that industry- and government-funded clinical trials are often conducted differently because the NIH is focused on public health issues.
For instance, an industry-funded trial of a blood pressure drug might test that drug against only a placebo and not against other drugs or diet and exercise, which an NIH-funded researcher would investigate, he said. Or an industry-funded trial of a drug for tumors might study a drug's ability to shrink a tumor, not its ability to extend a patient's life span or improve quality of life.
And, Ehrhardt said, the competition for NIH funding for clinical trials has intensified, as newer types of research such as genomics or personalized medicine also vie for funding.
Ehrhardt said he wants to spur debate on research funding.
"We need a discussion on how to best allocate our health-related research budgets," he said. "What best informs public health?"