Japan has long grappled with what to do about hikikomori – the social hermits who seal themselves off from the world, sometimes for years, retreating from all human contact.

In the past, these recluses were thought of as a youth problem: troubled teenagers, rudderless young men. But that framing no longer holds.

Japan’s shut-ins are growing old, and the parents keeping them alive are growing older still.

The average hikikomori is now 36.9 years old, according to the Asahi newspaper, citing a recent survey of 280 families conducted by Kazoku Hikikomori Japan (KHJ), an NGO providing support, guidance and community.

More striking still, the survey suggests more than 43 per cent of hikikomori are now over 40 and nearly 13 per cent are past 50. Their carers – overwhelmingly ageing parents – averaged 66.3 years old.