A total of 6,227 deaths were recorded between United Lincolnshire Hospitals Trust and Northern Lincolnshire and Goole Trust.
But the expected amount was estimated at 5,342, meaning 16% more patients died.
At Lincoln County, Boston Pilgrim and Grantham Hospitals, 3,706 patients died with an expected amount of 3,225, a 14% difference.
Scunthorpe and Grimsby hospitals recorded 2,521 patient deaths with an expected number of 2,117, a difference of 19%.
The Summary Hospital-level Mortality Indicator report shows the ratio between the actual number of deaths at a hospital and those that were expected to die.
Both ULHT and NLaG’s figures were higher than expected.
The report says that a higher than expected rating should not be interpreted as meaning bad performance.
Instead, it says it should be viewed as a “smoke alarm” which requires further investigation by the trust.
ULHT said in a statement: “Higher than expected SHMI rates do not mean that there were avoidable deaths.
“Mortality rates act like an alarm and they tell hospital trusts to look in detail at possible issues, and we use mortality data in this manner. Our HSMR mortality data is currently within expected range.
“This review looks at resources, the accuracy of the data being recorded as well as understanding if there were any failings in the care being delivered, and share lessons learned.
“Actions we are taking to improve our compliance include training for our staff to improve the way our staff record patient data, to ensure the SHMI data is more accurate.”
Acting medical director of NLaG, Dr Kate Wood, said that the trust is working closely with the health community in order to understand the figures.
She said: “Improving the quality of care for our patients is a key focus of the Trust’s Improving Together programme. While the overall SHMI position has not improved since the last publication, it has not deteriorated further which is an indication we are starting to see the impact of this work.
“These figures relate to the period October 2016 to September 2017. Since then we have appointed a new clinical lead for mortality and introduced hand held devices on the wards so observations can be recorded at the bedside.
“This allows patients whose condition is deteriorating to be identified more quickly. Our clinicians are also carrying out regular case note reviews and share learning.
“We know that patients who are already approaching the end of their life when they are admitted to hospital account for a high number of both the in-hospital and out of hospital deaths.
“We continue to work with our primary care colleagues and other community care providers to try to avoid admission of such people who would benefit from care management that does not necessarily involve hospital care.”
Calvin Robinson , Local Democracy Reporting Service