Chinese cyclists

The health benefits of physical activity are well established in high-income countries but previous studies have tended to focus on physical activity during leisure time. In China and many other low and middle-income countries few people engage in leisure time exercise as they have limited access to sports facilities and spend more time at work and doing household jobs. The main disease patterns also differ, for example, there are high rates of haemorrhagic stroke in China, for which evidence about the effects of physical activity is still limited.

Researchers from the China Kadoorie Biobank, Peking University and Chinese Academy of Medical Sciences studied 500,000 adults with a mean age of 51, from 10 urban and rural areas across China, tracking their health status through hospital records and death registries. In people with no history of cardiovascular diseases when recruited to the study there were 5,000 new heart attacks, 25,000 ischemic strokes, 5200 intracerebral haemorrhages and 8,400 cardiovascular deaths after 7.5 years. The associations of disease outcomes with self-reported total physical activity (including that during commuting, household and leisure time) were analysed and are published in JAMA Cardiology this week.

Metabolic Equivalents of Task (MET) describes the ratio of the rate of energy expended during an activity to the rate of energy expended at rest. The levels of total physical activity in MET hours per day (MET-h/day) were calculated according to frequency, duration and intensity of different types of reported activity. It was found that in this adult Chinese population the mean total physical activity was 22 MET-h/day, much higher than that typically seen in Western populations, with 62% due to occupation-related activities.

In all physical activity examined, each 4 MET-h/day higher physical activity (corresponding to about 1 hour of brisk walking per day) was associated on average with a 9% lower risk of heart attack, 6% lower risk of stroke and 12% lower risk of cardiovascular disease death.

The association was similar across different geographical study areas and in both men and women. However, the benefits of physical activity were much weaker in those with hypertension than those with normal blood pressure, especially for stroke. Hypertension was generally poorly controlled.

Those with higher total physical activity were more likely to be male, younger, living in rural areas, and be less educated than those with lower physical activity.