The number of people in China living with dementia has more than doubled over the past 20 years, a study has shown.

Disease rates are increasing faster than previously thought so much so that caring for dementia patients will soon cost health services more than tackling heart disease and cancer combined, experts have warned.

Latest figures show that in 1990, 3.68 million people had dementia in China and by 2010 this number had risen to 9.2 million.

Experts believe the increase could be explained by a combination of factors such as increased life expectancy in China and massive demographic, social, economic and lifestyle transitions that took place over the previous two decades.

The international study, led by the University of Edinburgh and published in The Lancet, reviewed almost 90 public health studies that included the health information of almost 350,000 people in China.

Scientists analysed the data to determine how many people had been diagnosed with dementia - including Alzheimer's disease - between 1990 and 2010.

Previous estimates by the World Health Organisation and other health bodies may have underestimated the burden of chronic diseases such as dementia in low- and middle-income countries, researchers say.

Experts warn that rapid government action is now required to tackle dementia in China and that lessons should be learned for the rest of the developing world.

Dr Kit Yee Chan, the lead author of the study at the University of Edinburgh, said: "Of the many chronic diseases that need attention worldwide, dementia is predicted to have the greatest economic and social effect. The number of dementia and Alzheimer's cases in China might pose the single largest challenge to health and social care systems in terms of finding appropriate and affordable responses."

Professor Igor Rudan, of the University of Edinburgh's Centre for Population Health Sciences, said: "A response purely from strained health services is unlikely to be sufficient, and wider societal action and innovative solutions will be needed. With one in four people older than 80 years likely to suffer from dementia in China, adequate resources should be provided at the national, local, family, and individual levels to tackle this rapidly growing problem."

Professor Wei Wang, a visiting Professor at the Centre and a joint corresponding author of the study, added: "Public awareness campaigns are needed to counteract common misconceptions about dementia - including that it is not very common in the Chinese population, that it is a normal part of ageing, or that it is better not to know about it because nothing can be done about it."