Dementia rates are increasing more rapidly in China than almost anywhere else in the world, with cases more than quadrupling in the country over the past few decades.

at Fudan University in China and her colleagues analysed dementia rates in 204 countries and regions around the world between 1990 and 2021. They used a World Health Organization database to collect information on dementia deaths and cases in people aged 40 and older, focusing on Alzheimer’s disease and some other forms of dementia, such as vascular dementia and frontotemporal lobe dementia.

The researchers found that the number of people with dementia worldwide more than doubled during this period, from almost 22 million in 1990 to close to 57 million in 2021. The increase was even more drastic in China, where cases more than quadrupled, rising from roughly 4 million to nearly 17 million over the same time frame.

Further analysis revealed that population growth was the main culprit. Birth rates in China spiked in the 1950s. “So those people are getting older today – they are now in their 70s, which is the highest risk group for dementia,” says at Yale University, who wasn’t involved with the study. “Many countries have baby boomers, but not as large a cohort as China’s baby boomers. So that’s the main issue.”

The team identified three other major factors contributing to China’s rising dementia rates. The first, smoking, almost exclusively affects men, as only 2 per cent of women in China smoke cigarettes while . This is in sharp contrast to wealthier countries such as the US and the UK, where smoking rates have steadily declined, says Chen.

One Western trend that China has echoed is a jump in rates of diabetes and obesity, particularly in the past few decades, both of which are risk factors for dementia. This is probably because people in China are adopting a more Western diet high in fats and calories, says Chen. He believes that dementia rates in China will eventually resemble those in the US or UK, as younger generations tend to smoke less than older ones. But the condition will still have a huge impact on China in the meantime.

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“Dementia is one of the most expensive diseases in the world. It requires a lot of caregiving and treatment,” says Chen. “And in terms of an ageing population, China is still the largest in the world. There are fewer young people taking care of a larger cohort of older people with dementia. So, these are all challenges.”