Gabriel Garcia Marquez battling with dementia

The brother of Colombian author Gabriel Garcia Marquez has disclosed that the 85-year-old Nobel laureate is suffering from dementia.

Jaime Garcia Marquez, a civil engineer, told a group of students at a lecture in the Colombian city of Cartagena that his elder brother often telephones him to ask basic questions.

"He has problems with his memory. Sometimes I cry because I feel like I'm losing him," he said.

The author, who has lived in Mexico City since 1961, is one of the most influential and highly acclaimed living authors. He won the Nobel Prize for Literature in 1982, and Carlos Fuentes, the late Mexican writer, described him as "the most popular and perhaps the best writer in Spanish since Cervantes". Garcia Marquez's most famous novel, One Hundred Years of Solitude, has been translated into 37 languages and has sold more than 20 million copies.

"He is doing well physically, but he has been suffering from dementia for a long time," said Jaime - the first person in the family to publicly speak about "Gabo"'s illness. "He still has the humour, joy and enthusiasm that he has always had. But it's a disease that runs in the family."

Both Garcia Marquez's younger brother and mother suffered from Alzheimers.

And indeed mental illness has been a feature of Garcia Marquez's writing. One Hundred Years of Solitude, an epic tale of seven generations of the Buendia family in a fictional Colombian village, begins with the story of a family unable to care for their senile grandfather. The General in His Labyrinth, charting the final days of Latin American liberator Simon Bolivar, shows a broken and confused elderly man.

Garcia Marquez was born in the small Colombian town of Aracataca, the inspiration for his fictional town of Macondo, in One Hundred Years of Solitude. He was raised mainly by his maternal grandparents, who had a huge impact on his life. His grandfather Colonel Nicolas Marquez was outspoken against the banana plantation massacres in the year of Garcia Marquez's birth, influencing the author to become a political activist, strong critic of North American "imperialism" and a close friend of Fidel Castro. Garcia Marquez was also involved in peace negotiations between the Colombian government and the FARC rebels.

His grandmother Tranquilina was a fervent believer in ghosts, spirits and magic - something evident in Garcia Marquez's "magical realism" writing style. In One Hundred Years of Solitude a Spanish galleon is beached in the jungle; the villagers suffer for years from a plague of insomnia; and a flying carpet swoops through the air.

Despite its cinematographic potential, Garcia Marquez never sold the film rights, although many of his other books were made into films. Love In The Time of Cholera, starring Javier Bardem, was filmed in Cartagena in 2007.