Diverse exercise routines associated with reduced risk of death

Regularly doing a mix of different types of physical activity may be best for prolonging the lifespan, but the associations aren't linear, pointing to a possible optimal threshold effect, suggests research published in the open access journal BMJ Medicine.

Variety rather than simply doing more of the same, is linked to a lower risk of death irrespective of total quantity, the findings show, although an active lifestyle is still important in its own right, emphasise the researchers.

While physical activity has consistently been associated with better physical and mental health and a lower risk of death, the evidence for the potential impact of different types of physical activity is less conclusive, explain the researchers. And it's not clear whether variety might trump quantity, they add.

To explore this further, they drew on data from 2 large cohort studies with repeated physical activity assessments over more than 30 years: the Nurses' Health Study (121,700 female participants) and the Health Professionals Follow-Up Study (51,529 male participants).

Participants in both groups reported their personal characteristics, medical history, and lifestyle information on enrolment, and subsequently every 2 years by completing questionnaires.

In both groups, information on walking, jogging, running, cycling (including stationary machines), lap swimming, rowing or callisthenics, tennis and squash or racquetball were recorded from 1986 onwards.

Questions on weight training or resistance exercise; lower intensity exercise, such as yoga, stretching, and toning; other vigorous activities, such as lawn mowing; moderate intensity outdoor work, such as maintenance and gardening; and heavy intensity outdoor work, such as digging and chopping, were all added subsequently.

Participants were also asked how many flights of stairs they climbed daily, assuming that each flight takes 8 seconds to ascend.

The analysis of total physical activity levels was based on 111,467 participants: 70,725 from the Nurses' Health Study and 40,742 from the Health Professionals Follow-Up Study. Analysis of physical activity variety was based on 111,373 participants: 70,725 women and 40,648 men.

The researchers calculated the MET score for each physical activity by multiplying the average time (in hours/week) spent on it by its MET value. METs measure how much more energy is burned during an activity than at rest.

The maximum number of individual physical activities was 11 in the Nurses' Health Study and 13 in the Health Professionals Follow-Up Study. Walking was the most frequent type of leisure physical activity in both groups; men were more likely to jog and run than women.

Participants with higher total physical activity levels were less likely to have health risk factors, including smoking, high blood pressure and high cholesterol. They were also more likely to weigh less (lower BMI) to drink alcohol, eat healthily, to be more socially integrated, and engage in a broader range of physical activity.

During the monitoring period of more than 30 years, 38,847 people died, 9901 from cardiovascular disease, 10,719 from cancer, and 3,159 from respiratory disease.

Total physical activity and most individual types of physical activity, except for swimming, were associated with a lower risk of death from any cause. But the associations weren't linear, and the associations for total physical activity levelled off after reaching 20 weekly MET hours, suggesting that there might be an optimal threshold, say the researchers.

Walking was associated with the lowest risk of death at 17% for those who did the most walking, compared with those who did the least, while climbing stairs was associated with a 10% lower risk.

The associations observed for the other types of physical activity (least vs most) were as follows: tennis, squash, or racquetball 15% lower risk; rowing or callisthenics 14% lower risk; weight training or resistance exercises 13% lower risk; running 13% lower risk; jogging 11% lower risk; and cycling 4% lower risk.

Greater variety of physical activity was associated with a lower risk of death. After adjustment for quantity, engaging in the broadest range of physical activity was associated with a 19% lower risk of death from all causes and a 13-41% lower risk of death from cardiovascular disease, cancer, respiratory disease, and other causes.

This is an observational study, and as such, no definitive conclusions can be drawn about cause and effect. And the researchers acknowledge various limitations to their findings. For example, physical activity data were self-reported, rather than being objectively measured.

MET scores were also assigned assuming active engagement, and the lack of information on intensity may therefore have misclassified true energy expenditures. And participants were mainly White, which might limit the generalisability of the findings, they suggest.

Nevertheless, the researchers conclude: "Overall, these data support the notion that long term engagement in multiple types of physical activity may help extend the lifespan".