Aerobic ('cardio') exercise linked to significantly lower risk of dying from flu or pneumonia in US

Large US survey results

Dr Webber and his colleagues therefore wanted to find out if specific types and amounts of physical activity might be associated with this reduced risk. They drew on the responses of 577,909 adults who had taken part in the US nationally representative National Health Interview Survey (NHIS) between 1998 and 2018. 

Respondents were asked how often they spent 10 or more minutes in vigorous intensity and light or moderate intensity aerobic activities, and they were asked how often they did muscle strengthening activities. Individuals were then categorised according to how well they met recommended aerobic activity plus muscle strengthening weekly targets: not meeting either; meeting the aerobic activity target; meeting the muscle-strengthening target; and meeting both targets.

Five levels of physical activity were defined: below 10, 10-149, 150–300, 301–600 and more than 600 mins/week of moderate to vigorous physical activity; and less than two, two, three, four-six and seven or more sessions/week of muscle strengthening activities.

Half the respondents (50.5 per cent) didn’t meet either weekly target. How well they did so differed significantly according to sociodemographic and lifestyle factors, underlying health conditions, and whether they had been vaccinated against flu and/or pneumonia.

A third (34 per cent) were aerobically inactive, and more than three quarters (78 per cent) reported fewer than two weekly sessions of muscle strengthening activities. During an average monitoring period of nine years, 81,431 participants died; 1,516 of these deaths were attributed to flu and pneumonia.

Those who met both recommended weekly physical activity targets had nearly half (48 per cent) the risk of dying from flu or pneumonia as their peers who met neither, after accounting for potentially influential factors. 

Efforts to reduce influenza and pneumonia mortality among adults might focus on decreasing the prevalence of aerobic inactivity and increasing the prevalence of achieving 2 episodes/week of muscle-strengthening activity [Bryant Webber et al]

Meeting only the aerobic activity target was associated with a 36 per cent lower risk, after accounting for potentially influential factors, while meeting only the muscle strengthening target wasn’t associated with any significant difference in risk.

Health benefits and aerobic physical activity 

In terms of quantity, clocking up 10–149, 150–300, and 301–600 mins/week of aerobic physical activity was associated with, respectively, 21 per cent, 41 per cent, and 50 per cent lower risks, compared with none. But no additional benefit was seen above 600 weekly minutes. 

‘Although [10-150 mins/week] is often labelled "insufficient" because it falls below the recommended duration, it may confer health benefits relative to physical inactivity,’ Dr Webber and his colleagues note.

When it came to muscle strengthening activities, compared with fewer than two weekly sessions, meeting the weekly target of two was associated with a 47 per cent lower risk, but seven or more sessions were associated with a 41 per cent higher risk.

Muscle-strengthening activities may help

‘While beyond the scope of this study, plausible explanations [for this dichotomy] range from inaccurate responses (such as reporting occupational physical activity, which may not confer the same protective effect as leisure-time physical activity) to haemodynamic ramifications of frequent, high-intensity [muscle strengthening activity],’ explain the researchers.

As an observational study, cause, cannot be established, added to which the researchers acknowledge various limitations. For example, the study relied on personal recall and at one point in time; the NHIS survey captured only leisure time physical activity in bouts of 10 or more minutes, nor did it distinguish between light and moderate intensity activities.

Nevertheless, the researchers conclude: ‘Efforts to reduce influenza and pneumonia mortality among adults might focus on decreasing the prevalence of aerobic inactivity and increasing the prevalence of achieving 2 episodes/week of muscle-strengthening activity.’

Factfile

Adults are advised to clock up at least 150 minutes/week of moderate intensity, or 75 minutes of vigorous intensity, aerobic physical activity, or an equivalent combination, plus muscle strengthening activity of moderate or greater intensity at least twice a week.

Aerobic exercise, which includes brisk/speed walking, swimming, running, and stair climbing, is sustained, increasing heart rate and working up a sweat. Muscle strengthening activities include the use of weights and resistance bands; exercises such as squats, lunges, and press-ups (calisthenics); and heavy gardening.

As well as helping to maintain good health and ward off serious illness, regular physical activity may also protect against death from flu or pneumonia, the evidence indicates.

To access the full version of the article – titled Research: Leisure- time physical activity and mortality from influenza and pneumonia: a cohort study of 577 909 US adults doi 10.1136/bjsports-2022-106644 – click