Presentation on theme: "National Diet and Nutrition Survey (NDNS) rolling programme"— Presentation transcript:
1National Diet and Nutrition Survey (NDNS) rolling programme Gillian SwanNutrition DivisionFood Standards AgencyThanks for invitation to speakThis talk to focus on NDNS programme. Will cover programme as it was and features of new rolling programme being set up.I will highlight some of the features of NDNS and differences between it and EFS and HSE which you heard about earlier.
2Food Standards Agency Aims include: To make it easier for all consumers to choose a healthy diet and so improve quality of life by reducing diet-related diseaseTo continue to reduce food-borne illness and the risks to consumers from chemical contamination of food throughout the UK.NDNS is funded and managed by FSA with DHFSA: Independent Government department set up to protect public health and consumers’ interests in relation to food.Aims:Both aims require dietary survey data to support work on nutrition and food chemical exposure assessment
3National Diet and Nutrition Survey programme (NDNS) Major component of Agency’s dietary survey programme.In its previous form - a series of cross-sectional surveys of different age groupsNow setting up a rolling programme to collect data continuouslySurveys of individuals
4NDNS programme as it was Series of cross-sectional surveys of diet and nutritional status covering discrete population age groupsDietary assessment - weighed record for four or seven daysBlood and urine sampleContextual information – physical measurements, physical activity, lifestyle characteristicsUsed weighed records in all age groups (4 or 7 days)Estimated record for foods eaten outside home.Blood sample – range of micronutrientsUrine sample – saltPhysical measurements – height, weight, blood pressure
5National Diet and Nutrition Survey Programme Slide shows surveys carried out in NDNS programmepre-school children early 1990sfollowed by:older adults 65 and over - mid 1990schildren and young people 4-18 yearslatest survey:adults yearsEach survey sample size N=Each survey published as printed report. Available from TSOIn addition reports of most recent survey of adults available on FSA websiteAll datasets available to researchers from the Data Archive
6Features of the NDNS Cross-sectional Data collected on individuals Detailed food consumption dataLinked data on food, nutrient intake, nutritional status and contextual information in individualsCross-sectional – no longitudinal element. Limitation for some types of analyses. Need care when analysing associations between diet and health measures eg diet and obesityIndividuals not households (EFS household purchases)Food consumption – food eaten not purchases
7Need for NDNS dataUnderpins Agency’s work to protect consumer safety & promote healthy diets.Detailed food consumption data essential for assessing exposure to food chemicalsAssess nutritional issues in the population and identify where action neededMeans of measuring progress towards Government targets and objectivesDetailed food consumption data for individuals essential for food chemical exposure assessments - part of risk assessment - risk management and communication. Protect consumers by making rapid and proportionate risk assessments. Eg. Mercury levels in oily fish. NDNS data identify population groups at risk so advice could be targeted at at risk groups.Agency targets to reduce salt and sat fat intakes by 2010.Compare intakes with nutrient intake recommendationsModel policy options eg. Fortification with folic acidSalt reduction strategy - needs data on contributors to salt intakes
8Why change the approach? Concerns about current programmeLack of timeliness - 15 year gap between surveysLack of flexibilityDeclining response ratesData quality (under-reporting)Agreement from Agency’s Board to move to rolling programmeI have outlined the features of the NDNS programme in its original form. Now move on to rolling programme. Why are we changing approach?Review following NDNS adults – highlighted some limitations of programmeResponse rates 80% 1986/ % 2000Response rates declining in all surveys.Lack of trend data – 15 year gap between 2 adult surveys. Increasing profile of nutrition – need to track changes in individuals
9Features of rolling programme Survey runs continuously - fieldwork every yearData points generated more frequently - better tracking of trends over timeGreater flexibility to collect additional data or boost sample for specific groups
10Features of rolling programme Core programme people per year (adults and children)All ages from 1½ years upwardsDesigned to be representative of the UK populationExcludes infants, pregnant women, people in institutionsSample adults and children every yearSample size minimum acceptable.RP will include Northern Ireland (not in previous NDNS)Considering sample boosts in devolved countries subject to funding. Possibility of other boosts e.g. ethnic minorities later
11Rolling programme – components (1) Face to face interviewDietary assessmentPhysical measurementsheightweightwaist and hip circumferencemid-upper arm circumference (children)Blood pressureComponents very similar to previous NDNSMeasurements by trained fieldworkers - interviewers / nurses in people’s homesDietary assessment – will say more about this later
12Rolling programme - components (2) Blood sample analysed for range of nutritional status indices24-hour urine collection (salt intake)Physical activity questionnairePhysical activity - relationship between intake and expenditure. Monitor under-reporting.Difficult to collect physical activity data by questionnaire especially in children. Piloting use of Actigraph monitors to measure physical activity (movement) in children.
13Dietary assessmentRequire detailed quantitative data on food consumed by each respondentWeighed record used for previous NDNS - but high respondent burdenResponse rates decliningConcern about under-reportingNow will say a bit more about dietary assessment.Response rates decliningweighed record method thought to be a factor - burdennon-response bias - are the data representative of UK population? Are diets of non-responders different from those of responders?Concern about under-reportingdoubly labelled water studies in previous NDNS indicate under-reporting at 25% of energy requirements on average.Occurs with all dietary assessment methods - not possible to prevent it entirelyNo accepted methods for correcting survey datasets for under-reporting
14Choice of Dietary Assessment Method Pilot work to compare two methodsMultiple pass 24 hour recall4 non-consecutive daysUnweighed diary4 consecutive daysCompare response rates and data quality to decide on best methodAbout to start pilot work to compare two methods:Multiple-pass 24 hour recallrepeated on 4 non-consecutive daysused in US NHANESused in UK low income surveyless burden for participants - response rates should be higherUn-weighed diary (4 days)Less burdensome than weighed recordHigher response rates?Never used in a national survey in the UKCheaper than recall - fewer fieldworker visitsBoth methods will collect 4 days data (consecutive / non-consecutive)On-going assessment of under-reportingphysical activityDLW
15NDNS rolling programme timetable Comparison study to choose dietary assessment method – spring 2007Dress rehearsal - early 2008Rolling programme fieldwork commences April 2008Results for first year 2008/09 available end of 2009Contract awarded end of last year to a consortium led by NatCen with UCL dept of epidemiology and public health and MRC HNR.
16Reports and DatasetsKey results published on FSA website annually (www.food.gov.uk)Datasets sent to the Data Archive annuallyPrinted report with commentary to cover first four years resultsWebsite – haven’t worked out format but likely to be tables that can be updated annually.
17How can the data be used? Monitor trends & progress towards targets Compare intakes with recommendationsDescribe characteristics of people with low (or high) intakes/statusModelling changes in diet or compositionOther uses ……..As sample size only 1000 per year will need to wait for few years for sample size to build up sufficiently to monitor trends. Possibility of sample boosts.eg. what do high salt consumers eatwhat do people with poor micronutrient status eatPeople with high vitamin A intakes – main dietary sourcesModelling - folate