But the health board says the figures do not tell the whole story.
After seeing the data, chief medical officer Nigel Millar looked into the issue.
The 11 patients were discharged from the emergency department rather than wards, he said.
If a patient had been in the emergency department longer than three hours, including any assessment and treatment, that counted as an admission and discharge, even if they had not been admitted to a ward.
Six returned home with the support of their families, four returned to aged residential care with appropriate support, and one had attended for a minor procedure and was well enough to return home unaccompanied at their request, he said.
"In all cases, I am satisfied this has been a result of appropriate clinical care."
If it was not appropriate or safe for an older person to be discharged from ED then they would either be admitted to an inpatient bed or remain in ED in an observation area until the following day when support could be arranged, he said.
"Admitting an older person to hospital unnecessarily is not always in the their best interests, as there are other potential risks that can be introduced during an inpatient hospital stay."
Many patients seen in ED also preferred not to be admitted, despite the time of day, he said.
"Any decision is planned in partnership with the older person and their family or carer to determine what is best for them with patient safety and their welfare as the most important considerations."
Millar yesterday said she felt sending people home in the middle of the night was disruptive, and she wanted the system to change to allow people to stay in hospital until the next day.
When asked about Millar's claims that the issue was a long-running one, Dr Millar said his priority was to ensure the 11 discharges "did not indicate an ongoing issue".