According to new research led by NDPH, Chinese people who regularly drink alcohol have significantly greater risks of developing severe liver diseases. The results are published today in BMC Medicine.
Liver disease is a major global health problem, causing over 2 million deaths each year. China is particularly affected, accounting for more than half of worldwide liver cancer cases and deaths. This is mainly due to the Chinese population having a high prevalence of chronic Hepatitis B Virus (HBV) infection, which attacks the liver and causes inflammation. Despite China introducing universal HBV vaccination for new-born babies in the 1990s, there are concerns that rapid economic development could cause liver diseases to become even more prevalent in China, as citizens shift to lifestyles with greater alcohol consumption.
Drinking too much alcohol is known to increase the risk of liver diseases, as this causes changes in lipid metabolism (leading to ‘fatty liver’), inflammation (hepatitis), and scarring (cirrhosis) in the liver. Up to now, however, most studies on these effects have been carried out on Western populations, with little evidence on whether the risks are the same for Chinese populations, where drinking patterns and people’s ability to metabolise alcohol differ.
Traditionally, drinking alcohol regularly has not been widespread in China, partly because many Chinese people have low tolerability to alcohol. This is due to a genetic mutation in an alcohol detoxifying enzyme (aldehyde dehydrogenase 2, ALDH2) which causes an unpleasant ‘flushing’ response and dizziness after only a small amount of alcohol. Potentially, this may make Chinese populations more vulnerable to the harmful effects of alcohol on the liver.
To investigate the link between alcohol consumption and liver diseases in China, NDPH researchers used data from the China Kadoorie Biobank (CKB) study. Almost half a million healthy participants completed detailed questionnaires about their drinking patterns, and were then tracked for an average of ten years through linkage to health insurance records and death registers. The researchers adjusted the data to take into account other factors that could affect health, including age, region of residence, education, income, smoking, physical activity and bodyweight.
Overall, 33% of men and 2% of women drank alcohol regularly (i.e. at least weekly). Of the men who drank regularly, 70% mainly drank spirits (at least 30% alcohol by volume).
During 10 years of follow-up, the study recorded 2531 cases of liver cancer; 2040 cases of liver cirrhosis; 260 cases of alcoholic liver disease (ALD), and 1262 cases of non-alcoholic fatty liver disease (NAFLD).
For men who drank regularly, there were significant positive relationships between how much they usually drank and their risk of all liver diseases. Each increase of 280g pure alcohol a week (roughly equivalent to four drinks a day) was associated with:
- a 44% increased risk of liver cancer;
- an 83% increased risk of liver cirrhosis;
- a doubled risk of ALD;
- a 71% increased risk of NAFLD;
- a 52% increased risk of all liver diseases.
Men who drank alcohol outside mealtimes had 32-60% higher risks of liver cancer, liver cirrhosis, and ALD, compared with those who only drank at mealtimes. In the absence of food, alcohol may be absorbed more quickly from the intestine, leading to higher blood alcohol concentrations and a greater impact on the liver. In addition, participants infected with HBV had significantly higher risks of all liver diseases, at all levels of alcohol consumption.
Given that very few of the Chinese women in the study drank alcohol regularly, the main analysis focused on men. However, for women who drank regularly, the risk of ALD was more than six times higher than those who did not drink at all.
Dr Pek Kei (Becky) Im (NDPH), one of the lead researchers, said: ‘Our study provides important new evidence that – just as in Western countries - reducing population-levels of alcohol consumption in China is a key preventive strategy for liver diseases. Certain drinking habits should also be particularly discouraged, such as daily drinking and drinking outside mealtimes.’