L3 - Evolution & Epidemiology of PA for Health

• Are we made to be PA? NO, we were to survive but aren’t made to be:

  • Had essential skills to survive (hunting, gathering, endurance, strength etc), wouldn’t have reached age of reproduction if not for these skills
  • Had ag, domestication, settlements etc come into place bringing more leisure time
  • Then PA became popular as believed influence normal development & health
  • Living conditions continue to improve, muscular activities important for things were done at that time
  • Wanted to do less PA, because not made for it
• Hunter-gatherers:

  • A Hadza adult spent nearly 10 of their waking hours without having any detectable motion
  • Optimised to be PA but not made for it
  • Hunter-gatherers tend to spend more time squating & kneeling more muscular work but not PA
  • HG’s gather 97% of their food but weren’t that PA at all
  • 2 big differences between hunter-gatherers & industrialised societies

  1. When they are active they are really active
  2. How they spend their time when they aren’t active, kneel or squat
• Exercise as Medicine:

  • The Indian physician Suhruta prescribed moderate daily exercise as early as 600BC for the treatment of diabetes
  • Use of PA for health is not new can be tracked back in 600BC
• 
  

  PA levels in NZ:

  • ½ of all adults (51%) did at least 2.5 hours of activity in the past week, spread out over the week - meet guidelines
  • Men are more likely (55.3%) than women (48.3%) to do at least 2.5 hours of activity in the past week, spread out over the week
  • 1 in 7 adults are PA for less than 30 mins per week
  • Pacific & Asian adults are less likely to be physically active than non-Pacific, non-Asian adults
  • Adults aged 75 years & over are less likely to be physically active than those under 75 years
• Most common types of PA for sport, exercise or recreation among adults in NZ = walking then gardening
• Biggest barriers to taking part in more PA’s for sport, exercise or recreation among NZ adults = other commitments taking priority
• Why are we less PA?

  • Urbanisation
  • Increase in motor vehicle use
  • Less transport-related PA
  • Increase in technology = more desk jobs
  • Decrease in manual operations
  • Less occupational PA
  • Technology increases in & around the home
  • Less household related PA
  • Busier lives, less understanding of the importance of PA
  • Less recreational PA
  • What we are wanting to achieve
• Public health defined:

  • “The science & art of preventing disease” → prolonging life & improving quality of life through organised efforts & informed choices of society, organisations, communities & individuals
• Public health seeks:

  • To improve the health of communities & populations (or sections of the community) & reduce inequalities in health status
• 5 key areas of public health:

  • Behavioural science/health education/health promotion
  • Biostatistics
  • Environmental health
  • Epidemiology
  • Health services administration
• Epidemiology:

  • Is the study (scientific, systemic, & data-driven) of the distribution (frequency, pattern) & determinants (causes, risk factors) of health-related states & events (not just diseases) in specialised populations (neighbourhood, school, city, state, country, global)
  • It is a cornerstone of public health
  • Shapes policy decisions
  • Targeting those for preventable health care (specific populations)
• “All parts of the body which have a function, if used in moderation & exercised in labours in which each is accustomed, become thereby healthy, well-developed & age more slowly, but if unused & left idle they become liable to disease, defective in growth & age quickly”
• Types of study in PA & health:

  • Epidemiological
  • Mainly observational
  • Allow nature to take its course & analyse relationships between indices of health status & other variables
  • Laboratory-based
  • Mainly experimental intervene to see what happens to some/all individuals
• Observational studies:

  • Descriptive
  • Case reports or series
  • Individuals
  • Analytic
  • Populations
  • Correlational
  • Individuals
  • Cross-sectional surveys
  • Case-control studies
  • Cohort studies
• Experimental studies:

  • Randomised, controlled trials
  • Individuals
• Correlational studies:

  • Characteristics of an entire population are used to describe the frequency of a health-related outcome in relation to some factor/s relevant to the research question or hypothesis
• Cross-sectional study:

  • Describe the prevalence of a health-related outcome in representative samples & relate this to personal or demographic characteristics
  • Snapshot, NO longitudinal
  • = Here & now
• Case-control study:

  • Also called retrospective study, the occurrence of a possible cause is compared between people known to have a disease (the cases) & a reference group who don’t have the disease (the controls)
  • Exposed & non-exposed group
  • Always retrospective because have outcome already
• Cohort study:

  • They begin with a group of people who are free of disease & determine their exposure to suspected risk factors. Subgroups are defined on the basis of exposure to the risk factor
  • Can be longitudinal
  • Eg low vs high PA
  • Look at occurrence of specific outcome
  • Can’t intervene as then becomes experimental
• Observation have limited ability to have a cause link with an outcome

  • As always opportunity of bias or factor that can come into play
• Experimental study:

  • Researchers intervene to change a variable in one or more groups & then measure the effect on the outcome of interest
  • Could measure a causality
  • More certain of the cause of the the outcome
• Measures of occurrence of health-related outcomes:

  • Prevalence
  • The proportion of individuals in a population that exhibits the outcome of interest at a specified time
  • Incidence
  • The number of new occurrences of an outcome that develops during a specified time interval