A massive assessment of high-deductible health plans shows that while they cut health spending they also prompt patients to reduce preventative health care. The study, completed by RAND Corporation, looked at more than 800,000 families across the US and found that when people shift to a high deductible insurance plan of at least $1,000 per person, their health spending declined by 14% on average.

Spending was also lower in high deductible households where health savings accounts were sponsored by employers. Some of the cut backs families experienced were reduced immunizations, cancer screenings and routine tests for diabetes. “We discovered that costs go down dramatically during the first year people are enrolled in high-deductible health plans, as long as the deductible is at least $1,000 per person,” said Amelia M. Haviland , a study co-author and a statistician at RAND, a nonprofit research organization in a news release. “But we also found concerning reductions in use of preventative care. This suggests people are cutting both necessary and unnecessary care.”

High-deductible plans have been gaining interest because they are more affordable than other plans. By 2009, 20% of Americans with employer-sponsored plans had high-deductible coverage. A 2010 study found that more than half of large employers offered at least one high deductible plan to their employees. Officials believe that health care reform will push even more people into high-deductible plans.

So what’s the real cost savings of having a high deductible plan? The study shows that the deductibles had to be at least $1000 in order for the savings to be significant. With high-deductible plans spending was lower both on inpatient care, outpatient care, and prescription drugs.  Rates of mammography, cervical cancer screening, colorectal cancer screening and blood tests were among preventative care that dropped with high deductible plans. “We saw that patients reduced preventive care, and if this persists, it is likely to have health consequences in the future,” Haviland said in a news release. “These cutbacks could cause a spike in health care costs down the road if people end up sicker and need more-intensive treatment.”