XNN001 Lecture 2 The epidemiology of nutrition and physical activity

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  • Determinants exist at varying levels. These include:‘Macro’ or ‘upstream’ level determinants, which are the cultural contexts in which people live, such as social, environmental and geographical.‘Meso’ or ‘midstream’ level determinants, which are the relationships between existing microsystems. For example, the connection between family experiences and school experience.‘Micro’ or ‘downstream’ level determinants, those immediately surrounding the individual, such as family, peers and school.Determinants that affect health in a positive way are referred to as protective factors (e.g. good nutrition) while determinants that affect health in a negative way are commonly known as risk factors (e.g. low levels of physical activity). This table which is also in the Module 1 document, shows the relationship between selected chronic conditions and modifiable risk factors. The table reflects data that was collected by the 2007-08 Australian National Health Survey (ABS).We can see that tobacco smoking, physical inactivity and poor diet are all linked to most major chronic conditions. This has implications for our professional practice, because a single chronic condition is often the result of multiple risk factors and therefore we need a comprehensive, interdisciplinary approach that addresses multiple risk factors in order to prevent and manage chronic conditions.
  • Food and nutrition policy – 1992Acknowledged need for monitoring/ surveillanceLimitations of collecting nutrition/ PA data in broad survey: restrictions on space in these surveys - dietary and physical activity information collected restricted to a limited base of broad indicators of diet and physical activity (e.g. fruit and vegetable consumption, leisure time physical activity) which may be insufficient to base policy and health promotion decisions on.Due to no regular/ consistent method of screening, in many instances these data are limited for observing trends in these behaviours in Australia over time, as sampling or measurement methods differ between data collection points or there may not be a regular schedule of data collection of all variables.
  • The regularity of the Australian National Health Survey allows for monitoring and surveillance of physical activity at the national level among adults. However, these measures of physical activity are restricted to LTPA and estimates of the total amount of time spent walking or in moderate or vigorous types of physical activities.- Crude dietary indicators allow for limited surveillance of dietary behaviours. Additional data about age, country of birth, rural/remote location and a range of socioeconomic indicators enable the examination and monitoring of dietary intakes and physical activity by various population subgroups.
  • Only two national dietary intake surveys have been conducted among Australian adults in the past 50 years; NNS used both a 24 hour recall and food frequency questionnaireconducted by different agencies different sampling and dietary data collection methods different food composition databasesprovide detailed information about dietary behaviours cross-sectionally, are limited for monitoring purposes because of their different sampling and measurement methodsCurrently, there is planning and consultation underway for a National Nutrition and Physical Activity Survey Program among adults. Preliminary information about the sampling and data collection methods suggest similarities with those employed in the 1995 National Nutrition Survey- which would provide the first opportunity in Australia to examine trends in dietary intakes over time, and therefore provide information for monitoring and surveillance of dietary intakes.
  • females aged 15 years and over consumed more fruit and vegetables overall than their male counterparts. 56% of females and 46% of males met the recommended daily intake of fruit10% of females and 7% of males met the recommended daily intake of vegetables  -total fat intake contributed 32% of energy intakes, and saturated fats contributed to 13% of total energy.
  •  - Among children aged 5–17 years, 25% were classified as overweight or obese (17% and 8% respectively - In the 2007 Children’s National Nutrition and Physical Activity Survey, 17 per cent of boys and girls were classified as overweight; 6 per cent were obese; Dietary behaviours 2007 Children’s National Nutrition and Physical Activity Survey:-61% per cent of 4–8 year olds consumed adequate fruit (excluding juice), compared to only 1% of 14–16 year old- 22% of 4–8 year old children and 5%of 14–16 year olds met the dietary guidelines for vegetable intake. 30% average total energy contributed by fat intake of children from each of the age groups was approximately 30 per cent. 13 – 14% Saturated fat intake -some micronutrient intakes such as calcium, sodium and magnesium are likely to be problematic, particularly for the 14–16 year olds who were the least likely to meet the recommended intakes.
  • 65% of respondents aged 15 years or more had exercised for fitness, recreation or sport during the two weeks prior to interview. - - Almost half (48%) of respondents walked for exercise in the two weeks prior to interview36% did some form of moderate exercise (exercise which caused a moderate increase in heart rate or breathing) 15% did vigorous exercise (exercise which caused a large increase in heart rate or breathing).
  • At the state level, there has been sporadic monitoring of dietary intakes and physical activity among adults. QLD:Recent data on various aspects of dietary intakes and physical activity is available from the Queensland Health Omnibus Survey. This survey, conducted at 2-3 year intervals in Queensland has the potential for monitoring and surveillance, however the scope of the diet and physical activity items included in the survey has differed from year to year, making monitoring and surveillance difficult. NSW:NSW Population Health Survey collected by the epidemiology branch of NSW Health - annual survey collects a range of information about dietary behaviours and physical activity. Broad focus, number of health outcomes - diet and physical activity measures that are available tend to be broad (rather than specific) indicators of these behaviours. Victorian Health Survey -primary source of epidemiological data on dietary behaviours and physical activity among adults living in Victoria. Annual survey, with measurement and sampling methods being similar in each wave of data collection, making the observation of trends and surveillance possible. Dietary data collected in the survey includes information on fruit and vegetable intakes, type of milk consumed, alcohol consumption and physical activity information includes total time spent in sedentary, moderate and vigorous physical activity.
  • Dietary behaviours are complex and are the culmination of a range of factors including access, availability and affordability to foods that, arguably, are beyond the realm of the individual and are characteristics of the food supply. This contrasts with physical activity, where there may be fewer contextual factors that may influence an individual’s behaviour. In understanding the epidemiology of dietary behaviours, nutrition-related health outcomes and trends among populations, an understanding of the food supply with which the population interacts is important. In bringing about better health among populations, the scope of public health nutrition extends beyond health promotion and policy strategies that encourage individuals to make more healthy dietary choices to ensuring that the available food supply also promotes these choices.
  • In Australia, information about household expenditure on food is collected periodically as part of the Australian Bureau of Statistics’ Household Expenditure Survey. Limitations of this data are that it does not collect information on the quantity of foods purchased and the descriptions of foods purchased are not sufficient to allow for analyses of nutrient contents. Information on food supply can take a variety of factors into account, including production, imports, export, industrial and animal use of food, and waste.Food Balance Sheets Provide information about the amount of food available for human consumption in a country in a given year from the FAOtakes into account production, changes in stocks, imports & exports, agricultural & industrial use of foodstuffsrelates only to primary producegive trends in food supply over time both within & between countries Relates to national average, provides estimates per kg of food per head per year OR per grams of food per head per day.Important– food availability data is not the same as food consumption data (i.e. Information on the availability of food does not tell us how much food is actually eaten).
  • To compare trends in ‘apparent’ food consumption over time: Still an estimate as not measuring actual intake at the household levelApparent Consumption Data Derived by ABS in way similar to food balance sheets, however reporting is not limited to primary produce Not used for all food products e.g. if there was a better way of deriving consumption or for foods for which all components of the equation were not available (some milk products, beer, eggs, wine, cheese etc)Gives overall trends & correlationsData is useful in nutrition planningLong term data minimizes daily & seasonal variationsLarge sample populations increase validity of conclusionsNo placebo effectNo participant error
  • ABS Household Expenditure Survey – food available not actual food consumed nor nutrients consumedRetail food salesHousehold food expenditureability to get data on volumes purchased increases participant burdenallows for analysis of trends over timecomparisons of expenditure patterns b/n households from different areas, households with different composition & households with different levels of income
  • There are many implications associated with the adoption of the NRVS. These include:Ongoing education of health professionals and food industry professionals in the use of NRVS and the related tools for their use;Need to update: The NHMRC Core Food Groups analysis, the Australian Guide to Healthy Eating, the Dietary Guidelines for Australian Adults, the Australian Guidelines for Children and Adolescents in Australia and the Dietary Guidelines for Older Australians;Need for regular monitoring of dietary intake and nutrient status in the population, including the use of fortified foods and supplements to assist in ongoing revisions of the NRVs, especially the AI values which are often based on population median dietary intakes;Need to update and expand existing food databases for the analysis of national nutrition surveys data, including levels of fortification in foods;The need to change computerised dietary analysis programs that use the existing RDI values as reference values;The need for the redevelopment of relevant standards for the use of NRVs for food legislative purposes, including issues such as food labelling and food fortification;The need to consider the implications of changes in the NRVs for the food and dietary supplementation industry.
  • Validity is therefore how ‘accurately’ a measure is quantifying what it is designed to measure.  There are many instances in dietary and physical activity research where error may affect our estimates of the population’s behaviours: Mistakes in the handling of mixed dishes: may lead to incorrect estimates of their nutrient content.
  • Random error is just that: random. It can occur during data collection, coding, transfer, or analyses. Examples of random error include: poorly worded questions, a misunderstanding in interpreting an individual answer from a particular respondent, or a typographical error during coding. Random error affects measurement in a transient, inconsistent manner, and it is impossible to correct for random error. Precision in epidemiological variables is a measure of random error. Precision is also inversely related to random error, so that to reduce random error is to increase precision. Confidence intervals are computed to demonstrate the precision of an estimated ‘true’ value. The narrower the confidence intervals, the more precise the estimate. To reduce random error: Increase the sample size of the study (theory behind this is that with a large enough sample size the degree of under-estimation will equal the degree of over-estimation, and therefore cancel each other out). - Reduce the variability in measurement (use a more precise measuring device or by increasing the number of measurements).
  • A systematic error is when a measure mis-estimates a ‘true’ value, and this mis-estimation is either consistently lower or consistently higher than the true value (e.g. if a food frequency questionnaire consistently under-estimates fat intake compared to ‘true’ fat intake). Because the error happens in the same direction in every instance, it is regarded as ‘systematic’. Systematic error is of greater concern than random error in population-based studies, as it is more likely to contribute to incorrect clinical judgments about the population’s health and health-related behaviours. One of the best ways to deal with systematic errors, is to use multiple measures of the same construct

Transcript

  • 1. THE EPIDEMIOLOGY OF PHYSICAL ACTIVITY AND NUTRITION IN AUSTRALIA XNN001 Population nutrition and physical activity assessment
  • 2. Chronic conditions internationally  35% of adults over 20 years overweight, 12% obese  Global prevalence of diabetes estimated to be 10% in adults aged 25+ years (221 million people)  151 million with osteoarthritis  64 million with chronic obstructive pulmonary disease (symptomatic cases)  54 million with angina pectoris  31 million were stroke survivors
  • 3. Chronic conditions in Australia  28% of adults 18 years and over obese, 35% overweight  17 per cent of boys and girls overweight; 6 per cent obese  17% of the population have one or more long term conditions of the circulatory system  32% of the population have hypertension  Chronic conditions account for 80% of the total burden of disease
  • 4. Chronic conditions and modifiable risk factors (AIHW, 2012) 4
  • 5. Population-level dietary and PA data in Australia  Often collected as a component of broad surveys (e.g. National Health Surveys)  Changing measures and sampling methods- limited evaluations of trends  No systematic data collection
  • 6. National Health Survey  Alcohol consumption  Fruit & vegetable intake  Physical activity level  Household food security
  • 7. Nutrition Surveys in Australia  National dietary surveys among adults- 1983, 1995, 2011-12  Children’s surveys 1985, 1995, 2007  Conducted by different agencies – different sampling & data collection methods, different food composition tables
  • 8. Diet  48% met recommendations for fruit  9% met recommendations for vegetables  ~ 5% meet recommendations for both fruit and vegetable  Total fat intake provided ~32% of energy  SF 13% total energy (1995 NNS)  <5% of households food insecure ((2004/05 NHS)
  • 9. Diet children  Low proportion meeting recommendations for F&V  Saturated fat intake high  Intakes of some micronutrients high
  • 10. Physical activity  67% adults had sedentary or low levels of physical activity  66% of school children participated in PA, however for most this was less than 2 hours per week  95% of school children participated in sedentary leisure time activities, for most this made up 10 – 19 hours
  • 11. State-level data  Differs by state  QLD- no systematic approach to collecting information about population diet and PA  Qld Omnibus survey  Qld cancer council risk study (2004)  NSW & Vic- regular Population Health surveys
  • 12. Extending beyond surveys of individuals  Food supply data  Nutrient composition of foods  Australian Household Expenditure Survey  International comparisons
  • 13. Food supply data  To calculate ‘available food for consumption’ – Food balance sheets  Information on amounts of food (raw commodities) available for consumption per year Food available for use = production + imports – exports  Food available for consumption =  production + imports – exports – industrial use – animal use  Important – food available for consumption does NOT tell us how much food is actually eaten!
  • 14. Food supply data  To compare food trends within Australia Apparent food consumption data Apparent consumption = (commercial production + estimated home production + imports + opening stocks) (exports + usage for processed foods + non-food usage + wastage + closing stocks) MINUS
  • 15. Tables of food composition  Used to:  Convert information about food intake to nutrient intake  Contain:  Nutrient data that is an average of nutrients in a particular sample of foods & ingredients, determined at a particular time  Need to:  Be current  Match the food supply NOTE: The nutrient composition of foods & ingredients can vary substantially over different batches, & between brands because of a number of factors including: • Changes in season • Processing practices • Ingredient source
  • 16. Limitations of food composition tables  Limitations:  Food supply changes quickly  Biological variation of foods  Single values representing range  Incomplete data – missing foods & nutrients  Bioavailability not considered  Potential measurement & data entry error  Relate to food supply of that country
  • 17. Food purchasing and acquisition  Household food expenditure  budget surveys  provides data on amount of money/proportion of income spent on food by different kinds of households  provides weighting figures for CPI (Consumer Price Index)  not measuring foods or nutrients
  • 18. Population-based recommendations  Nutrient reference values (NRVs)  Food-based dietary guidelines  Physical activity guidelines- children, adults, older adults
  • 19. Nutrient Reference Values  Retain the concept of the RDI  Provide more complete information for decision making about nutritional status of individuals and groups  Outline the levels of intake of essential nutrients considered to be adequate to meet the known nutritional needs of practically all healthy people for prevention of deficiency states.
  • 20. Nutrient Reference Values  The document can be used by health professionals to assess the likelihood of inadequate intake in individuals or groups of people.  NRV is ‘umbrella term’, there are different NRV values for different nutrients: • EAR – Estimated Average Requirement • AI – Adequate Intake • RDI – Recommended Dietary Intake • UL – Upper Limit of Intake • EER – Estimated Energy Requirement • SDTs – Suggested Dietary Target • AMDRs – Acceptable Macronutrient Distribution
  • 21. Nutrient requirements  Developed using reference (standard) body weights for different age groups  Estimated Energy Requirements (EERs) include physical activity level (PAL) consideration but refer to standardised weight for age  Adults well above and below the reference standard will have slightly different nutrient requirements (use RDI)
  • 22. Estimate Average Requirement – EAR  Daily nutrient level estimated to meet the requirement of half the healthy individuals in a life stage/gender group (ie median value)  Uses: Individuals: use to examine the probability that usual intake is inadequate Groups: use to estimate the prevalence of inadequate intakes within a group
  • 23. Recommended Dietary Intake -RDI  Average daily dietary level sufficient to meet the nutrient requirements of NEARLY ALL (97-98%) healthy individuals in a life stage & gender group  Uses: Individuals: usual intake at or above this level has a low probability of inadequacy Groups: DO NOT USE TO ASSESS GROUPS
  • 24. Adequate Intake – AI  Average daily intake based on observed or experimentally-determined approximations or estimates of nutrient intake by a group of apparently healthy people that are assumed to be adequate  Used when an RDI can not be determined  Uses: Individuals: can be used as a goal for individual intake but use with caution if nutrient level is based on median intakes of healthy populations Groups: if mean intake is at or above this level, a low prevalence of inadequacy is likely
  • 25. Upper Limit – UL  Highest level of continuing daily nutrient intake likely to pose no adverse health effects in almost all individuals  Uses: Individuals: usual intake above this level may place an individual at risk of adverse effects from excessive nutrient intake Groups: use to estimate the % of the population at potential risk of adverse effects from excessive nutrient intake
  • 26. Summary of the uses for the NRVs NRV Individuals Groups EAR Use to determine probability usual intake is inadequate Use to estimate prevalence of inadequate intakes within group RDI Usual intake at or above this level has a low probability of inadequacy DO NOT USE TO ASSESS INTAKES OF GROUPS AI Usual intake at or above has a low probability of inadequacy. When AI is based on median intakes of healthy population, interpret with caution. Mean usual intake at or above this level implies a low prevalence of inadequate intake. When AI is based on median intakes of healthy population, interpret with caution. UL Usual intake above this level may place individual at risk of adverse effects from excessive intake Use to estimate % of population at potential risk of adverse effects from excessive nutrient intake
  • 27. Dietary Guidelines 2013 (NHMRC)  Recommendations (‘guidelines’) which encourage healthy lifestyles that will minimise the risk of the development of diet related diseases within the Australian population  Highlight the groups of foods and lifestyle patterns that promote good nutrition and health  Available in ‘Eat for Health’ publication
  • 28. Dietary Guidelines 2013  Focus on:  Contribution of core foods & major sources of energy (fat, starch & sugar) to the overall diet  Provide:  A practical way of informing consumers about food choices that are consistent with current dietary recommendations  Separate guidelines for adults and children & adolescents
  • 29. Dietary guidelines 2013  Outlines how many serves a person should have of each food group based on their:  age  gender  body size (to a degree)  activity level (to a degree)  Provides examples
  • 30. Dietary Guidelines 2013 – notes for use  Summarise current nutrition knowledge  Trigger more comprehensive education programs  Represent best consensus of scientific knowledge  For use by healthy adults  Apply to whole diet not to individual foods  Guidelines are meant to be complementary not separate items  Not appropriate for cross cultural issues or unusual habits
  • 31. PA recommendations Australia’s Physical Activity Recommendations for 5-12 year olds  For infants (birth to one year) physical activity – particularly supervised floor-based play in safe environments – should be encouraged from birth.  Toddlers (1 to 3 years) & Pre-schoolers (3 to 5 years) should be physically active every day for at least three hours, spread throughout the day.  Children younger than 2 years of age should not spend any time watching television or using other electronic media (DVDs, computer and other electronic games) and for children 2 to 5 years of age these activities should be limited to less than one hour per day.  Infants, toddlers and pre-schoolers should not be sedentary, restrained, or kept inactive, for more than one hour at a
  • 32. PA recommendations Australia’s Physical Activity Recommendations for 5- 12 year olds  Children need at least 60 minutes (and up to several hours) of moderate to vigorous physical activity every day;  Children should not spend more than two hours a day using electronic media for entertainment (e.g. computer games, TV, Internet), particularly during daylight hours. Australia’s Physical Activity Recommendations for 12-18 year olds  -12-18 year olds should be doing at least 60 minutes of moderate to vigorous physical activity every day to keep healthy;
  • 33. PA recommendations National Physical Activity Guidelines for Adults  Think of movement as an opportunity, not an inconvenience;  Be active every day in as many ways as you can;  Put together at least 30 minutes of moderate- intensity physical activity on most, preferably all, days;  If you can, also enjoy some regular, vigorous activity for extra health and fitness.
  • 34. PA recommendations Recommendations for Physical Activity for Health for Older Australians  Older people should do some form of physical activity, no matter what their age, weight, health problems or abilities;  Older people should be active every day in as many ways as possible, doing a range of physical activities that incorporate fitness, strength, balance and flexibility;  Older people should accumulate at least 30 minutes of moderate intensity physical activity on most, preferably all, days;  Older people who have stopped physical activity, or who are starting a new physical activity, should start at a level that is easily manageable and gradually build up the recommended amount, type and frequency of activity;  Older people who continue to enjoy a lifetime of vigorous physical activity should carry on doing so in a manner suited to their capability into later life, provided recommended safety procedures and guidelines are adhered to.
  • 35. Measurement issues  Error- validity  when an estimate (eg, incidence, prevalence, mortality) or association (RR, OR) deviates from ‘true’ situation in nature  May be introduced at any point during the study: Study design (quality) sampling Measurement Analysis Random error Systematic bias
  • 36. Random error  Fluctuations around a true value  Related to poor precision  Sources individual biological variation (always present)  sampling variation measurement variation (protocols and training)  Reduced by:  larger sample sizes  standard protocols and equipment
  • 37. Systematic bias  Any systematic error in the design, conduct or analysis of a study that results in a mistaken estimate of an exposure’s effect on the risk of a disease  Due to causes other than random error  Problem of validity  internal and/or external validity