Before now, little was understood about the trade-offs between the health benefits of outdoor physical exercise and the potentially adverse consequences of air pollution. This is the first time it has been looked at in people aged 20 to 39 years old over a period of many years. Furthermore, the researchers decided to see what occurs as people gradually increase or decrease their physical activity.
Limited Physical Exercise – Air pollution
A study conducted by researchers from Seoul National University College of Medicine (South Korea) examined data from South Korea’s National Health Insurance Service (NHIS) for 1,469,972 young Koreans residing in cities who had two consecutive health tests during two screening periods: 2009-2010 and 2011-2012.
They kept track of their participants from January 2013 to December 2018. These participants were made to complete a questionnaire about their physical activity in the previous seven days at each health check-up. This detail was translated into units of metabolic equivalent task (MET) minutes per week (MET-mins/week).
These participants were grouped into four classes based on their MET-mins/week: 0, 1-499, 500-999, and 1000 or more.
According to the European Society of Cardiology recommendations, people can aim for 500-999 MET-mins/week, which can be attained by, for example, biking, swimming, or hiking for 15-30 minutes five days a week, or fast walking, doubles tennis, or slow cycling for 30-60 minutes five times a week.
The researchers used data from South Korea’s National Ambient Air Monitoring System to measure annual average levels of air pollution, specifically levels of small particulate matter with diameters smaller than or equal to 10 or 2.5 microns, known as PM10 and PM2.5.
The level of air pollution exposure was divided into two categories: low to moderate (less than 49.92 and 26.43 micrograms per cubic meter, m/m3, for PM10 and PM2.5, respectively) and extreme (49.92 and 26.46 m/m3 or more, respectively).
According to Dr. Rae, it was observed that in young adults aged 20-39 years old, the risk of cardiovascular disorders, such as stroke and heart attack, increased as the amount of physical exercise declined between the two screening periods in the population with low levels of exposure to air pollution.
On the flip side, the group which was exposed to higher levels of air pollution, raising physical exercise to more than 1000 MET-min/week, which is higher than globally recommended levels for physical activity, can have a negative impact on cardiovascular health.
Significantly the results indicated that, unlike middle-aged people over 40, excessive physical exercise might not necessarily be good for cardiovascular wellbeing in younger adults when exposed to elevated levels of air pollution.
It was observed criticality that air emissions should be reduced at the national level in order to maximize the health effects of exercise in young adults. These are the individuals who participate in more physical activities than other age ranges when their physical capacity is at its peak.
If air quality is not improved, cardiovascular diseases will actually rise, despite the health benefits of exercise.
The researchers changed their findings to account for potential confounding variables such as age, gender, household income, body mass index, smoking, and alcohol intake. There were 8706 coronary injuries during the follow-up era.
Those who increased their workout from 0 to 1000 MET-min/week or more during the two screening intervals had a 33% increased risk of cardiovascular disease during the follow-up period relative to those who were physically inactive and did not improve their exercise.
People exposed to low to moderate levels of PM2.5 who increased their physical activity from zero to 1000 MET-min/week or more had a 27% lower chance of developing cardiovascular disease than those who were inactive. However, this finding was not statistically important.
This suggests that during the follow-up era, 49 fewer individuals per 10,000 are likely to experience cardiovascular disease.
Results are extremely similar to statistical significance. A further review reveals that statistical significance was obtained for increasing and declining levels of physical activity.”
Statistically, it was observed that 38 percent or 22 percent of increased risk of cardiovascular disease for people who started out doing 1000 MET-min/week or more and then decreased their exercise to zero or 1-499 MET min/week, respectively, as opposed to people who retained the same high level of activity with low to moderate levels of PM10 air pollution.
“Overall, our findings indicate that physical exercise, especially at the level recommended by European Society of Cardiology recommendations, is associated with a lower risk of developing cardiovascular disease among young adults,” said lead researcher Professor Sang Min Park.
Exercising when air pollution levels are high, beyond the recommended amount may offset or even reverse the beneficial effects.”