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