Housewife Miyuki Yanagisawa cannot recall the last time she had sex with her husband. She is certain, though, that their physical estrangement can be measured in years, not months.

While she shares a room with the couple's two young daughters, her husband, a company employee, sleeps alone in another room, grateful for the chance to catch up on his sleep after another tortuously long day at work.

'As long as he is healthy and doing well at work, I can put up with the lack of affection,' Yanagisawa, 44 - who asked that her real name not be used - said of her decade-old marriage. 'Many other women in my age group feel the same. When couples reach a certain age they start calling each other "Mum" and "Dad" - they certainly stop using affectionate nicknames. I think that spells the beginning of the end for sex.'