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National Diet and Nutrition Survey (NDNS) rolling programme

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Presentation on theme: "National Diet and Nutrition Survey (NDNS) rolling programme"— Presentation transcript:

1 National Diet and Nutrition Survey (NDNS) rolling programme
Gillian Swan Nutrition Division Food Standards Agency Thanks for invitation to speak This 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.

2 Food 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 disease To 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 DH FSA: 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

3 National 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 groups Now setting up a rolling programme to collect data continuously Surveys of individuals

4 NDNS programme as it was
Series of cross-sectional surveys of diet and nutritional status covering discrete population age groups Dietary assessment - weighed record for four or seven days Blood and urine sample Contextual information – physical measurements, physical activity, lifestyle characteristics Used weighed records in all age groups (4 or 7 days) Estimated record for foods eaten outside home. Blood sample – range of micronutrients Urine sample – salt Physical measurements – height, weight, blood pressure

5 National Diet and Nutrition Survey Programme
Slide shows surveys carried out in NDNS programme pre-school children early 1990s followed by: older adults 65 and over - mid 1990s children and young people 4-18 years latest survey: adults years Each survey sample size N= Each survey published as printed report. Available from TSO In addition reports of most recent survey of adults available on FSA website All datasets available to researchers from the Data Archive

6 Features of the NDNS Cross-sectional Data collected on individuals
Detailed food consumption data Linked data on food, nutrient intake, nutritional status and contextual information in individuals Cross-sectional – no longitudinal element. Limitation for some types of analyses. Need care when analysing associations between diet and health measures eg diet and obesity Individuals not households (EFS household purchases) Food consumption – food eaten not purchases

7 Need for NDNS data Underpins Agency’s work to protect consumer safety & promote healthy diets. Detailed food consumption data essential for assessing exposure to food chemicals Assess nutritional issues in the population and identify where action needed Means of measuring progress towards Government targets and objectives Detailed 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 recommendations Model policy options eg. Fortification with folic acid Salt reduction strategy - needs data on contributors to salt intakes

8 Why change the approach?
Concerns about current programme Lack of timeliness - 15 year gap between surveys Lack of flexibility Declining response rates Data quality (under-reporting) Agreement from Agency’s Board to move to rolling programme I 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 programme Response rates 80% 1986/ % 2000 Response 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

9 Features of rolling programme
Survey runs continuously - fieldwork every year Data points generated more frequently - better tracking of trends over time Greater flexibility to collect additional data or boost sample for specific groups

10 Features of rolling programme
Core programme people per year (adults and children) All ages from 1½ years upwards Designed to be representative of the UK population Excludes infants, pregnant women, people in institutions Sample adults and children every year Sample 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

11 Rolling programme – components (1)
Face to face interview Dietary assessment Physical measurements height weight waist and hip circumference mid-upper arm circumference (children) Blood pressure Components very similar to previous NDNS Measurements by trained fieldworkers - interviewers / nurses in people’s homes Dietary assessment – will say more about this later

12 Rolling programme - components (2)
Blood sample analysed for range of nutritional status indices 24-hour urine collection (salt intake) Physical activity questionnaire Physical 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.

13 Dietary assessment Require detailed quantitative data on food consumed by each respondent Weighed record used for previous NDNS - but high respondent burden Response rates declining Concern about under-reporting Now will say a bit more about dietary assessment. Response rates declining weighed record method thought to be a factor - burden non-response bias - are the data representative of UK population? Are diets of non-responders different from those of responders? Concern about under-reporting doubly 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 entirely No accepted methods for correcting survey datasets for under-reporting

14 Choice of Dietary Assessment Method
Pilot work to compare two methods Multiple pass 24 hour recall 4 non-consecutive days Unweighed diary 4 consecutive days Compare response rates and data quality to decide on best method About to start pilot work to compare two methods: Multiple-pass 24 hour recall repeated on 4 non-consecutive days used in US NHANES used in UK low income survey less burden for participants - response rates should be higher Un-weighed diary (4 days) Less burdensome than weighed record Higher response rates? Never used in a national survey in the UK Cheaper than recall - fewer fieldworker visits Both methods will collect 4 days data (consecutive / non-consecutive) On-going assessment of under-reporting physical activity DLW

15 NDNS rolling programme timetable
Comparison study to choose dietary assessment method – spring 2007 Dress rehearsal - early 2008 Rolling programme fieldwork commences April 2008 Results for first year 2008/09 available end of 2009 Contract awarded end of last year to a consortium led by NatCen with UCL dept of epidemiology and public health and MRC HNR.

16 Reports and Datasets Key results published on FSA website annually ( Datasets sent to the Data Archive annually Printed report with commentary to cover first four years results Website – haven’t worked out format but likely to be tables that can be updated annually.

17 How can the data be used? Monitor trends & progress towards targets
Compare intakes with recommendations Describe characteristics of people with low (or high) intakes/status Modelling changes in diet or composition Other 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 eat what do people with poor micronutrient status eat People with high vitamin A intakes – main dietary sources Modelling - folate

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