Unflinching Athill lands Costa book award at 91

Former literary editor is oldest winner of prize, for memoir that drew plaudits for its honesty about sex and death

A 91-year-old who wrote a unflinching memoir encompassing the end of her sex life, the intimacies of ageing and the prospect of death has become the oldest writer to win a Costa prize.

Diana Athill, who won the biography category yesterday, triggered an immense nationwide response from readers and critics after writing her sixth and most frank memoir, Somewhere Towards The End, dealing with thorny themes surrounding ageing such as a dwindling desire for sex and physical frailties such as sore feet.

When published last year, it sparked heartfelt responses at readings across the country. The Costa judges hailed it as "a perfect memoir of old age", adding that it was "candid, detailed, charming, totally lacking in self pity or sentimentality and, above all, beautifully, beautifully written".

The book is a series of interlinked essays that touch on everything from atheism to gardening and caring. Athill, a former literary editor, said its success could be due to its frank nature, because for "a long time age and death were taboo subjects in this country ... I think the fact that I'm in my nineties and still compos mentis, and able to write and have a nice time, is encouraging to people. They can look at me and say, 'There is somebody who is old – which I am dreading – but there, it's not so bad.' "

She admitted she had some hesitation about writing a detailed account of old age, and nearly dismissed the notion as "a dreary subject". Yesterday, a spokeswoman for Athill said she was suffering from influenza but was "delighted" to have been selected as the category winner.

Athill is one of five writers who take home a £5,000 prize for winning their category. The others were Sebastian Barry for his novel, The Secret Scripture; Michelle Magorian with her children's book, Just Henry, which she wrote after a 10-year hiatus; and two debut writers, Sadie Jones, whose first novel, The Outcast, was a best-seller, and Adam Foulds, whose debut poetry collection about the Mau Mau uprisings in Kenya is called The Broken Word. He has previously written a novel.

Barry, whose book was shortlisted for the Booker last year, also focused on history and old age. The protagonist in his novel is a 100-year-old woman in an asylum. He said: "I'm interested in this [ageing and death] and always have been. It's the threshold between one stage of being and another but in our culture, we have discarded the importance of it. Old people are in places where we can't hear what they say."

The overall winner of the £25,000 Costa Book of the Year prize will be announced on 27 January. If Athill wins, she will be its oldest recipient. Born in 1917, she worked for the BBC during the Second World War. She later helped to establish the publishing company Andre Deutsch and went on to write five memoirs including the highly-acclaimed Stet. Over 50 years in publishing, she worked closely with the authors Philip Roth, John Updike, Norman Mailer, Simone de Beauvoir, and V S Naipaul. She retired in 1993.

Almost there: The other category winners

*Costa First Novel Award: The Outcast, by Sadie Jones

Jones's first novel is about a teenager fresh out of jail and travelling back to his home in southern England in 1957. His tale is interwoven with a storyline about his father's return to the same suburban landscape after the Second World War a decade earlier.

*Costa Novel Award: The Secret Scripture, by Sebastian Barry

Focuses on the uncertain future of its protagonist, Roseanne McNulty, who is nearing her 100th birthday in a mental hospital where she has spent most of her adult life. Described by judges as an "exquisitely written love story".

*Costa Children's Book Award: Just Henry, by Michelle Magorian

Goodnight Mr Tom author Magorian's first book in 10 years centres on a young boy in post-war Britain who hates his stepfather and believes his natural father died a war hero. Henry escapes his bleak life through a passion for cinema.

*Costa Poetry Award: The Broken Word, by Adam Foulds

A debut work of poetry by Foulds charting a young man's progress through a dark period in British colonial history – the Mau Mau uprisings in Kenya – which takes in tribal violence and retribution. Epic, and described as Homeric.