Costs for employer sponsored-medical plans in 2018 are likely to rise 8.4 percent – nearly triple the projected rate of inflation, as global risk factors such as high blood pressure, physical inactivity and obesity increase, according to Aon's report, "2018 Global Medical Trend Rates."

For 2018, the gap between the average medical trend rate and the average general inflation rate is expected to modestly decrease to 5.3 percentage points from the corresponding 5.4 figure in 2017. The average nominal medical trend rate is expected to increase 0.2 percentage points: For 2018, the global average medical trend rate was 8.4 percent and the average general inflation rate was 3.1 percent. In 2017, the global average medical trend rate was 8.2 percent and the average general inflation rate was 2.8 percent.

"Aon expects further medical cost escalation due to global population aging, overall declining health, poor lifestyle habits becoming pervasive in emerging countries, continuing cost shifting from social programs, and increasing utilization of employer-sponsored plans," the authors write.