The latest British Social Attitudes survey also revealed 52 per cent of the general public considered themselves non-religious.
However, that figure dropped to only 15 per cent among NHS patients.
Rev Declan McConville, lead chaplain at Poole hospital in Dorset, told Premier what could be behind the figures.
Speaking during Premier's News Hour, he said: "When someone is in hospital, it kind of concentrates your priorities. Gives you an opportunity to reflect of the meaning of life, I suppose.
"It could also awaken a faith that's there - most of our older population will have a Christian background."
While 40 per cent of the population described themselves as Christians, the figure rode to 66 per cent among admitted patients, according to the data obtained at the Manchester University NHS Trust.
The results were taken from the more than 260,000 patients treated at the trust over the past five years who were asked about their religious affiliation.
Listen to Premier's Alex Williams speaking with Rev Declan McConville:
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