BEIJING - Middle-aged Shanghai residents are turning to ketamine, cocaine and methamphetamine to sustain them through marathon sessions of mahjong and cards, a state newspaper has warned.

Until now, authorities have focused on drug abuse by the young and reckless, and while most users in the city are teenagers and young professionals, officials say that a growing number of older inhabitants are turning to drugs as well.

A spokesman for the Shanghai Anti-Drugs Commission, Zheng Yuqing, told the China Daily that there had been a ''significant increase'' in cases among the middle-aged, although he declined to give figures.

''Most of the older victims, aged between 40 and 60, are unemployed or retired and so have plenty of spare time. They are often not well educated and have little awareness of the harm caused by taking drugs,'' he said.

The newspaper said many older people used drugs as a stimulant during card-playing and mahjong sessions, which often last all night. Gambling is often a big part of the lure, although it is illegal on the mainland.

''The drug-taking mostly occurs among groups in card rooms, a place popular among the elderly where they can get together and play cards.

Population

Shanghai has a rapidly greying population. More than a fifth of its residents are over 60, according to official statistics, and the proportion is rapidly increasing.

''More and more middle-aged and older people take drugs because they feel lonely and empty after retiring or losing their jobs,'' the secretary-general of Shanghai Sports Association for the Aged, Li Luyan, told the China Daily.

Shanghai had a reported 48,000 registered drug addicts last year, up from 42,000 in 2008. Mahjong games can tax even youthful participants. Last year a 30-year-old man slipped into a coma after playing for 32 hours non-stop, state media reported.