Studies over the years have suggested that too many patients receive certain "low-value" health care services that run up costs, but aren't always very helpful.

A new study takes a large sample of claims data collected by Optum, the Eden Prairie-based data division at UnitedHealth Group, and looks at how often a group of 1.46 million adults used 28 low-value services during 2013.

The answer: Nearly 115,000 patients received low-value services in 2013 resulting in $32.8 million in spending, which was about 0.5 percent of total spending during the period.

That works out to about $22 per person, according to the study published Monday as a research letter in the medical journal JAMA Internal Medicine.

The most commonly received low-value services: Hormone tests for thyroid problems; Imaging for low-back pain; and imaging for uncomplicated headache. In terms of dollars, the biggest driver of cost was spending for spinal injection for lower-back pain at $12.1 million, according to the report from researchers at RAND Corporation and the University of Southern California.

Imaging for uncomplicated headaches ran up an estimated $3.6 million in costs, while imagining for non-specific low-back pain cost $3.1 million.

In the study write-up, researchers said there's an estimated $750 billion of wasteful health care spending each year in the U.S., including about $200 billion in over treatment.

"Reducing overuse could improve quality and access while reducing spending," researchers wrote in the journal article.

The study found that low-value spending per $10,000 in total spending was less among patients who were older, male, black or Asian, low-income or enrolled in health plans with big deductibles.

"Efforts to reduce waste in health care may be bolstered by measure development efforts that focus on over treatment, insurance designs that discourage overuse and programs that target groups and regions at greater risk of low-value care," researchers wrote in the medical journal.