Stagnant funding for federal health statistics is raising concerns among medical professionals, patient advocates and other groups that one of the national surveys used to assess the death rate from opioid abuse and average life expectancy may soon disappear.

Funding for the National Center for Health Statistics has fallen from $166 million five years ago to $160 million this year. And while the Senate is proposing a $1 million increase for health statistics for fiscal 2019, the House has proposed level funding and the Trump administration is calling for a $5 million cut.

The funding lag for statistics comes even as Congress has boosted funding for medical research, drug approvals and other health programs to record levels, while lawmakers, health providers and law enforcement increasingly step up their efforts to curb the nation’s opioid crisis.

“Any kind of health policy decision you’re going to make — a lot of it depends on those surveys,” said former Census Bureau chief John H. Thompson, who now heads the Council of Professional Associations on Federal Statistics.

Thompson’s group advocates statistics programs across the federal government, and in May, along with dozens of other organizations, suggested that the NCHS needs $175 million for fiscal 2019.

The NCHS is among 13 agencies across the government responsible for crunching numbers in a variety of fields. Housed within the Centers for Disease Control and Prevention, the agency runs several surveys that are large enough to be considered representative of the nation as a whole.

The National Health Interview Survey has been running since 1957 and asks questions about individuals’ health status and access to medical care. From this, the CDC produces reports that can inform or assess health policy, like how many Americans have health insurance, or why people go to hospital emergency rooms.

The National Health and Nutrition Examination Survey goes a step further, conducting physical examinations of its participants in addition to interview questions. It results in studies that range from the makeup of people’s diets to the amount of lead in an average person’s blood.

The statistics agency also produces drug overdose death counts that it updates monthly. And it recently reduced the time it takes to report deaths after they occur from a year to about 6 months with a goal of reducing the lag even further.

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But even as the CDC’s budget has grown, the NCHS hasn’t kept pace.

Since 2012, the CDC’s overall budget grew from about $6.4 billion to roughly $7.3 billion in fiscal 2018. At the same time, funding for health statistics fell slightly — a fairly typical trend for statistical agencies across the government.

At the Labor Department, the Bureau of Labor Statistics received $612 million for fiscal 2018, which follows gradual increases over the last few years but represents just about $1 million dollars more than it had in 2010.

The Bureau of Economic Analysis at the Commerce Department received $99 million in fiscal 2018, a $10 million decrease compared to two years earlier. And the Justice Department’s statistics division is funded at $99 million in fiscal 2018, down from $116 million in 2016.

The Senate’s proposed $1 million increase for health statistics and the level funding proposal from the House for 2019 has health organizations ranging from professional associations to patient advocacy groups concerned that at least one of the national surveys could disappear.

“Despite making marginal adjustments to accommodate years of budget cuts, including reducing sample size and delaying necessary survey innovations, the agency cannot responsibly sustain these surveys if its funding level dips below the amount it received in FY 2018,” dozens of groups wrote in a May letter to House and Senate appropriators.

The groups argue that the surveys are becoming more expensive to administer, especially because more resources are being spent to recruit participants as response rates have declined. Thompson said there are many reasons for this trend, including shifting modes of communication, people becoming increasingly mobile and a general distrust in the government.

The loss of one of these surveys would likely deal a blow to health researchers looking at emerging trends or the effect of policy, even as Congress increasingly subsidizes research into new cures and treatments. The National Institutes of Health’s budget reached $37.1 billion in 2018, up from $29 million five years ago, and is poised for another $2 billion increase in 2019.

“These are unique resources that can’t be replicated by the private sector,” Mary Jo Hoeksema, government affairs director for the Population Association of America, said of the surveys. The nonprofit science professionals organization, along with Thompson’s group, has spearheaded the letters to Congress on behalf of health statistics in recent years.

The Trump administration has requested a $5 million funding decrease for the NCHS, which it says would allow it to continue providing quality information and maintain health data systems at “current functionality,” according to the fiscal 2019 justification to Congress. It is also proposing reducing the size of the agency’s nationwide surveys to “the lowest sample size which permits the production of estimates on key health indicators at the national level.”

The groups warn, however, that shrinking the size of the surveys would likely not be enough to sustain them financially in the long term, and could potentially undermine their validity.

“At some point, you’re just not going to produce estimates that people can rely on,” Thompson said.