Hong Kong  - It's one of the sunniest cities in the world, but more than six out of 10 people in sub-tropical Hong Kong get too little sunshine, according to a survey published Sunday.

More than 62 per cent of people examined for a University of Hong Kong study were found to be suffering from vitamin D deficiency even though about two-thirds of the days in the year are sunny and hot.

Lifestyle is believed to be a major factor, as most people in the high-rise city shun the sun and exercise, while working long hours in offices.

The three-year study, reported in the Sunday Morning Post newspaper, found that a majority of people over 50 years of age were deficient in vitamin D.

Vitamin D, which is absorbed primarily through exposure to sunlight, strengthens muscles and bones and helps people avoid osteoporosis and bone fractures.

Professor of medicine Annie Kung told the newspaper it was "hard to believe" people living in a sub-tropical city could suffer from a deficiency of the vitamin.

Hong Kong, with a population of 7 million, is one of the world's most densely populated cities, with many people living in apartment blocks above shopping centres.

People often do not need to emerge into the open air on their way to work, using an extensive underground rail network with covered walkways leading to office blocks.

Other recent surveys have indicated that Hong Kong people are among the world's most sedentary with few taking regular exercise and obesity rates rising steeply. dpa