There were 234,000 admissions in the UK in the quarter, according to data collected from over 650 private hospitals.
Richard Wells, PHIN's director of technology and insights, said the slowdown could reflect an improvement in NHS waiting lists, a change in the type of procedures and way they are delivered, such as the increasing popularity of anti-obesity medicines, or the increase in remote healthcare.
The decline was seen across each of the UK nations except for Scotland: England 206,465 admissions (-3%); Northern Ireland 5,765 admissions (-3%); Scotland 13,455 admissions (+3%); and Wales: 8,015 admissions (-2%).
Cataract surgery (19,150) remained the top procedure, with chemotherapy (18,540) in second and diagnostic upper gastrointestinal (GI) endoscopy (11,325) in third. Chemotherapy was the only procedure in the top 10 by volume of admissions that increased.
When looking at just admissions funded with private medical insurance, chemotherapy (17,240) was the top procedure with almost double the number of admissions of diagnostic upper GI endoscopy (9,890) in second place.
The most popular procedures among self-paying patients using their savings or a loan for their treatment were: cataract surgery (11,795), hip replacements (3,910) and knee replacements (1,930).
During the same period, private hospitals and clinics also conducted over 1.3m NHS funded procedures. The majority of these were in ophthalmology and trauma and orthopaedics.
