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SCMP Reporter

Sleep disorders are common in a city that is never quiet

Millions of people could be suffering from sleep disorders, mood swings, anxiety and other psychological problems because of Hong Kong's permanent 'surround sound' environment, say experts.

Wong Tze-wai of Chinese University's Department of Community and Family Medicine said research into residents' exposure to environmental noise - known as ambient noise - showed that as many as one in four people living in housing estates near areas with heavy traffic suffered sleep disorders.

'We measured the noise levels at a housing estate next to a major highway and found the ambient level was 70 decibels,' Professor Wong said.

'This is very high for environmental exposure - it's quite noisy and not very pleasant when you finish work and hope to enjoy a peaceful evening at home,' he said.

In the workplace, a noise level of more than 85 decibels for eight hours a day over five days is considered to be potentially harmful to hearing.

While the noise in housing estates is below that level, 'even a background noise level of 60 decibels affects sleep or wakes us from sleep', Professor Wong said.

The pilot study, which has not yet been released, is believed to be the first attempt to assess the health impact of noise in Hong Kong.

According to a report by public policy think-tank Civic Exchange, European studies estimate that the cost of damage to society from noise  ranges from 0.2 per cent to 2 per cent of gross domestic product. Based on these figures, the annual cost of noise to Hong Kong could be in the order of $2.5 billion to $25.4 billion.

The government spends millions of dollars on addressing workplace-related damage to hearing alone.  The Occupational Deafness Compensation Board last year received more than 260 applications, awarding almost $8 million to claimants. Since 1995 the board has approved more than 2,000 applications and paid $200 million in compensation.

Michael Tong Chi-sai, of the ear, nose and throat team at Chinese University's Department of Surgery, said levels of environmental noise were not in the same range as occupational noise, but at highs of between 75 and 80 decibels in some areas of the city, it was nonetheless potentially harmful.

'Environmental noise levels are high but not high enough to cause physical damage to people's hearing. Mainly the damage is psychological, although some elderly people can't use hearing aids because of environmental noise,' he said.

'Noise is very annoying and people get tense. It can change behaviour and affect communication.'

Dr Tong said attempts to drown out background noise, for example by listening to music through headphones, were not advisable because it could lead to even greater damage and hearing loss. 'A lot of kids put the music volume up to around 95 to 100 decibels. That can cause damage in just half an hour.'

The Environmental Protection Department received close on 6,370 complaints about noise last year - a third of its caseload.

Officials say keeping environmental noise from causing a severe disturbance to the public is 'particularly challenging' in a compact, high-rise city like Hong Kong.

Measures to combat the problem have been in force since the mid 1980s, including resurfacing roads to counter traffic noise,  building  barriers along major roads and  controlling noisy industries and activities with regulations.



Noise levels linked to health problems