Week 1- PA and life expectancy

Question 1

A prospective cohort analysis (Zaccardi et al 2024)

Answer 1

Adding a 10-min brisk walk to daily habitual PA patterns was modelled to result in a longer life expectancy of 0.9 years in the least active women and 1.4 years in the least active men.

Question 2

Accelerometer vs self-reprt

Answer 2

• Association of PA with life expectancy is stronger with accelerometer assessed compared to self-reported measures, supporting the importance of objectively quantifying the impact of PA on survival using device-based measurement.

Question 3

Epidemiological cohort studies

Answer 3

On their own they cannot show cause and effect

Question 4

Meta- analysis (Samtiz et al)

Answer 4

The most physically active had a 35% reduction in mortality risk.
- A dose-response relationship between amount of PA and mortality risk was observed.
- Minute-for-minute, engaging in vigorous exercise and sports was associated with greater reductions in all-cause mortality than engaging in walking/ moderate intensity PA.

Question 5

Ekelund et al. 2019 - published a meta-analysis of prospective cohort studies that measured physical activity using accelerometery and assessed risk of all-cause mortality

Answer 5

The study demonstrated that any physical activity, regardless of intensity, was associated with lower risk of mortality.
The relationship was not linear, with the largest benefits seen in moving from the first to second activity quartiles.
Undertaking just ~ 5– 6 minutes per day of MVPA was associated with a ~ 30% reduction in mortality risk

Question 6

Lee et al. 2012- A report in The Lancet, based on self-reported measures of physical activity

Answer 6

It was estimated that 9.4% of all deaths could be attributed to physical inactivity, and if everyone who was inactive, became active, it was estimated that worldwide life expectancy would increase by 0.68 years.

Question 7

Patterson et al 2018 meta-analysis - Sedentary behaviour

Answer 7

• Each additional hour of total sedentary behaviour below a threshold of 8 hours per day was associated with a 1% increase in mortality risk, whereas every hour above 8 hours per day was associated with a 4% risk increase.
• Every hour of television viewing below 3.5 hours per day was associated with 3% increase in risk of mortality, whereas every additional hour beyond this was associated with a 6% increase in mortality risk.
  The association between sedentary behaviour and mortality risk is not linear, with risk only increasing steeply for individuals who report sitting for more than about a third of the day, or watch more than three to four hours of television per day.
  The association between television viewing and risk of mortality is substantially stronger than the risk associated with overall sitting.

Question 8

Ekelund et al 2016: meta-analysis on sitting

Answer 8

Risk of mortality associated with high levels of sitting can be mitigated by being sufficiently active

Question 9

A meta-analysis by Kodama on cardiorespiratory fitness

Answer 9

• Overall, each 1-MET increase in cardiorespiratory fitness (equivalent to a 1 km h –1 faster maximum intensity running speed) was associated with a 13% reduction in mortality risk.
• Higher levels of fitness was associated with lower risk of mortality in people with a range of health conditions; including cardiovascular disease, diabetes and COPD, and In those exhibiting a range of risk factors for CV or metabolic disease.

Question 10

Muscular strength and mortality

Answer 10

Leong et al 2015: grip strength was inversely associated with risk of mortality, with each 5kg decrement in grip strength associated with a 16% increase in risk of all-cause mortality.
Katzmarzyk and Craig 2002: found that the number of sit-ups performed in 60 seconds was associated with all-cause mortality

Question 11

Recent evidence from UK Biobank suggests that the association between PA and risk of mortality may differ according to level of cardio-respiratory fitness and grip strength

Answer 11

Data suggest that the mortality risk associated with a low level of physical activity is greatest in those with low levels of fitness and strength, and that those with high fitness and strength have relatively low risk of mortality, even when their physical activity levels are low.

Question 12

Nurses’ Health study - PA, fitness, and body composition

Answer 12

Found that physically active women with obesity had a 30% lower mortality risk compared to inactive women, though their risk remained higher than physically active women of normal weight.
Overall, evidence suggests that low levels of physical activity and obesity are independent and additive risk factors for all-cause mortality.

Overall, evidence indicates that physically active obese individuals have lower risk of mortality than inactive obese individuals, but that a high level of activity does not fully protect from the excess mortality risk associated with obesity.

Question 13

RCTs

Answer 13

It is very difficult to undertake randomised controlled trials to investigate the effects of physical activity on risk of mortality because of the low absolute risk of mortality over a given time period for individuals in the general population.
- Thus, a study will need to be extremely large and long for sufficient deaths to occur to be able to establish whether increasing physical activity changes risk of mortality amongst the general population.
One way to address this issue is to study older populations where the risk of mortality is higher.

Question 14

Summary:

Answer 14

• Observational studies consistently show that physical activity is inversely associated with risk of mortality.
• Both vigorous and moderate intensity physical activity are associated with lower mortality risk, but minute-for minute, vigorous activity is associated with a greater risk reduction.
• There is an accumulating body of evidence that participation in muscle-strengthening exercise, as well as aerobic physical activity, is associated with lower risk of mortality.
• It has been estimated that almost 10% of deaths worldwide can be attributed to physical inactivity.
• Sedentary behaviour is associated with risk of mortality in a non-linear manner, with mortality risk increasing by ~4% per hour increase in daily sitting time beyond 8 hours.
• A stronger association with mortality is observed for TV viewing than overall sitting.
• Risks associated with high levels of sedentary behaviour according to level of physical activity can be minimised by being sufficiently active.
• Both cardiorespiratory fitness and muscular strength (usually assessed using hand grip strength) are inversely associated with risk of mortality. These associations are stronger than the association between physical activity and mortality risk and may reflect more accurate measurement and/ or the genetic contribution to fitness and strength influencing risk independent of physical activity.
• Risks associated with physical inactivity appear to be greatest in those who also have low levels of fitness or strength
• Obese individuals with a high level of cardiorespiratory fitness appear to have similar risk of mortality as fit normal wight adults. However, a high level of fitness is substantially less common in obese than normal weight individuals.
• Available evidence suggests that those with the highest level of physical activity or cardiorespiratory fitness have approximately 1.5 to 4 years longer life expectancy than those with the lowest levels of activity/ fitness.