information:classification, linguistic:voice_change
Later life and death

Kao's international travels led him to opine that he belonged to the world instead of any country. An open letter published by Kao and his wife in 2010 later clarified that "Charles studied in Hong Kong for his high schooling, he has taught here, he was the Vice-Chancellor of CUHK and retired here too. So he is a Hong Kong belonger."

Pottery making was a hobby of Kao's. Kao also enjoyed reading Wuxia (Chinese martial fantasy) novels.

Kao suffered from Alzheimer's disease from early 2004 and had speech difficulty, but had no problem recognising people or addresses. His father suffered from the same disease. Beginning in 2008, he resided in Mountain View, California, United States, where he moved from Hong Kong in order to live near his children and grandchild.

On October 6, 2009, when Kao was awarded the Nobel Prize in Physics for his contributions to the study of the transmission of light in optical fibres and for fibre communication, he said, "I am absolutely speechless and never expected such an honor." Kao's wife Gwen told the press that the prize will primarily be used for Charles's medical expenses. In 2010 Charles and Gwen Kao founded the Charles K. Kao Foundation for Alzheimer's Disease to raise public awareness about the disease and provide support for the patients.

In 2016, Kao lost the ability to maintain his balance. At the end-stage of his dementia he was cared for by his wife and intended not to be kept alive with life support or have CPR performed on him. Kao passed away at Bradbury Hospice in Hong Kong on September 23, 2018 at the age of 84.