Week 1 Lecture - All cause mortality

Question 1

what is PA

Answer 1

Any bodily movement that uses skeletal muscle and requires energy, excluding sitting or lying down

Question 2

what is sedentary behaviour?

Answer 2

Waking behaviour characterised by an energy expenditure ≤1.5 METs, while in a sitting, reclining or lying position

Question 3

Fitness definition

Answer 3

The ability to perform daily tasks and the state of being physically healthy

Question 4

Findings from Samitz et al (2011) meta-analysis

Answer 4

• compared lowest and highest PA groups- 24% higher risk of dying
• dose response relationship

Question 5

Does intensity matter (Samitz et al 2011)?

Answer 5

• For any given duration, vigorous intensity is best for reducing relative risk of all cause mortality
• Each minute of vigorous exercise per day reduces risk of mortality
• Every 10mins of vigorous exercise equates to 35minutes of moderate exercise

Question 6

Objective vs Subjective measures

Answer 6

Objective measures see a greater reduction in mortality risk

Question 7

Accelerometer based findings (Meta-analysis: Ekelund et al 2019)

Answer 7

• Higher MVPA and light activity reduced mortality risk
• Something is better than nothing
• Undertaking 5-6mins of MVPA per day was associated with a 30% lower risk of mortality

Question 8

UK biobank analysis (Zaccardi et al 2024)

Answer 8

• 10mins of brisk walking per day was associated with a longer life expectancy of 0.9 years in inactive women and 1.4 years in inactive men

Question 9

Women’s health study (Kamada et al 2017)

Answer 9

• Over 146 mins per week of strength training producing a higher risk of mortality compared to someone doing no strength training
• 82 mins a week of strength training produced the lowest risk of mortality
• benefits of strength training seem to be additive to aerobic exercise (up to a certain point)

Question 10

How many deaths worldwide are attributed to physical inactivity

Answer 10

9.4%

Question 11

Self - report measures

Answer 11

• underestimate mortality risk

Question 12

Sedentary time and all-cause mortality (Patterson et al 2018 meta-analysis)

Answer 12

• Below 8hours/day sedentary time = 1% increase in mortality risk per additional hour
• Above 8 hours/day sedentary time = 4% increase in mortality risk per additional hour
• Below 3.5 hours/day TV viewing time - 3% increase in risk per additional hour
• Above 3.5 hours/day TV viewing time - 6% increase in risk per additional hour
• Non-linear relationship of sedentary behaviour and mortality: risk only substantially increases once sedentary time hits 8hours/day.

Question 13

Does high PA offset the negative effects of sedentary time? Ekelund et al 2016

Answer 13

• Sitting less than 4 hours/day associated with 27% higher risk of mortality in inactive vs active participants
  -Does-response relationship with those who are sitting longer with all-cause mortality risk
• High physical activity offsets the negative effect of high sitting time on mortality risk. This is not seen at low physical activity

Question 14

Regularly active definition

Answer 14

Meeting physical activity guidelines over 5+ days (spread out across the week)

Question 15

Insufficiently active definition

Answer 15

Doing some activity but not meeting the guidelines

Question 16

Weekend warrior

Answer 16

Cramming activity into the weekend or spreading it out across the week does not affect all cause mortality risk

Question 17

Mortality risk of sedentary behaviour

Answer 17

Sedentary behaviour is associated with risk of mortality in a non-linear manner, with mortality risk increasing by ~4% per hour increases in daily sitting time beyond 8 hours.

Question 18

Fitness and all-cause mortality

Answer 18

• Fitness is a more accurate marker of all-cause mortality than PA data
• Myers et al: Those in the lowest fitness group had the highest risk of mortality
• Högström et al, 2016 - High fitness at 18 years of age was associated with a low risk of all-cause mortality compared to those who were unfit at 18

Question 19

Key Lecture points:

Answer 19

• Fitness and strength are inversely associated with risk of mortality, and this association is stronger than with physical activity (more accurate measurement)
• Risks associated with physical inactivity appear to be greatest in those who also have low levels of fitness or strength
• Evidence suggests that obese individuals who are physically active have a lower risk of mortality than inactive obese individuals, but a high level of physical activity does not fully protect from the adverse effects of obesity on mortality risk.
• Obese individuals with a high level of cardiorespiratory fitness appear to have similar risk of mortality as moderately fit normal weight adults.