Asia Bibi is displaying symptoms of dementia at an "early" stage, according to a campaign group trying to free her - the British Pakistan Christian Association (BPCA).
The Association cited a recent visit to Bibi by a Pakistani journalist who suggested her memory, mental sharpness and judgement were in decline.
Bibi was found guilty under Pakistan's strict blasphemy laws in November 2010 after being accused of insulting the Islamic prophet Mohammad and drinking from the same water source as Muslims in June 2009.
For most of the past nine years, Bibi has been held in solitary confinement inside a Pakistan prison cell - sentenced to death, despite support from high-profile figures including the Pope.
Concerned solitary confinement has had a serious toll on Bibi's welfare, Wilson Chowdhry from the BPCA said: "No divine being needs human help which makes blasphemy laws so petty and ridiculous.
"Yet, the intolerant nature of Muslims in Pakistan has meant an innocent mother-of-five has lost a relationship with her family and through the onset of dementia, she may never be able to bond effectively with them again.
"If delays in her Supreme Court appeal take any longer, then the freedom we have all hoped to gain for her will be extremely shallow and will quickly become a new period of isolation."
A description given by a Pakistani journalist of Bibi's condition was examined by an assistant nurse with links to the BPCA who said she considered Bibi's symptoms to be dementia-related.
The report suggests an account the BPCA received 18 months ago from a cleaner at Bibi's prison who described similar behaviour. It is relatively unusual for anyone under 65-years-old to develop dementia.
According to the BPCA, it has so far remained impossible for Bibi to undergo a test for dementia while she is behind bars.
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