Physician referral rates in the United States has doubled between the years of 1999 and 2009, according to a new study, and this is mainly linked to the increasing costs of health care.

The rise in referral amounts correlate with an increase in chronic illnesses, such as Type 2 diabetes. The estimated absolute tally of visits resulting in a referral went up by 159 percent, from 40.6 million to 105 million.

“If you add that up, it’s real money,” said chief study author Bruce Landon, professor of health care policy at Harvard Medical School, in a statement.

The research team found a 92 percent increase in referral rates (from 4.83 to 9.29 percent) over the last decade, analyzing a nationally representative sample of 845,243 ambulatory patient visits from the National Ambulatory Medical Surveys, from 1993 to 2009.

“Understanding trends in physician referrals is critical both for improving patient care and for managing costs,” conveyed Michael Barnett, author of the study.

For several years the amount of physician referrals remained consistent, up until ten years ago. This is principally due to increased specialization in medical care, and having primary care physicians do more than they typically do during a patient visit.

“Sometimes physicians may find it easier to refer a patient to another doctor than to find the necessary time to spend with him or her, said Zirui Song, a co-author of the study.

The results of the study were published in the current issue of the Archives of Internal Medicine.