Week Two - Diet Assessment methods

Question 1

common approach in large epidemiologic studies:

Answer 1

FFQ and 24 hour recall ( to help calibrate FFQ)

Question 2

a source of measurement error in which measurements consistently depart from true value in same direction; affects sample mean as well as percentiles and can result in incorrect estimates and conclusions

Answer 2

bias (systematic error)

Question 3

measurable substance in an organism whose presence is indicative of some phenomenon such as disease, infection, or enviro exposure

Answer 3

biomarker

Question 4

process of using equations to rescale data obtained from more-biased, less-accurate instrument based on info obtained from less-biased, more-accurate instrument

Answer 4

calibration

Question 5

study that compares two groups of ppl: those with disease or condition under study, and a very similar group of ppl who don’‘t have disease/condition

Answer 5

case control study

Question 6

study that includes measurements on a group of individuals at a single interval in time

Answer 6

cross-sectional study

Question 7

reporting error that is diff in nature or magnitude between two groups

Answer 7

differential response bias (differential error)

Question 8

the explanatory variable, also referred to as independent variable in regression model–often a behaviour such as diet

Answer 8

exposure

Question 9

the target variable, also referred to as the dependent variable in regression model; often a health outcome like the occurrence of a specific disease

Answer 9

outcome

Question 10

what is reactivity?

Answer 10

change in behaviour due to awareness that behaviour is being measured–may bias result

Question 11

type of biomarker directly related to intake and not subject to homeostasis or substantial inter-individual diffs in metabolism

Answer 11

recovery biomarker (ie. doubly labelled water, urinary nitrogen)

Question 12

probability that a test correctly rejects null hypothesis when alternative hypothesis is true

Answer 12

statistical power

Question 13

deviation from accurate report related to a variety of factors that affect an individual as they respond to verbal/written question

Answer 13

response bias

Question 14

stat method for correcting estimated regression coefficients for bias due to measurement error in one or more continuous covariates. Used to adjust relative risk estimates for measurement error in studies of the association of diet and health outcomes

Answer 14

regression calibration

Question 15

the Primer made for clinic or research?

Answer 15

research

Question 16

random vs systematic?

Answer 16

unpredictable (day to day fluctuations) and can be adjusted for using repeat measures and stat modelling; measurement consistently depart from true value in same direction (eg. underreport sweets), cannottbe adjusted for without availability of reference measure that contains no or error or only random error

Question 17

systematic error in food diary?

Answer 17

subject burden–>lower quality data, record consumption less often so be like a recall, reactivity

Question 18

food records good for:

Answer 18

describe diet intake and examine association between diet and other variables, support individuals to make recommended diet changes

Question 19

error in 24 hour recall?

Answer 19

day to day variation (random), underestimate energy intake,

Question 20

why is 24 hour recall considered least biased of self report instruments?

Answer 20

no reactivity bias

Question 21

systematic error of FFQ?

Answer 21

not capture entire diet, difficulty of recall task

Question 22

FFQ are popular in ___ because ___

Answer 22

large prospective epidemiological studies/retrospective case control; ease of administration, low cost, asks about diet retrospectively, gets less frequently consumed foods

Question 23

common use of screeners?

Answer 23

large cross-sectional studies when interview time/resources limited for a few diet factors

Question 24

4 research objectives?

Answer 24

describe diet intake, examine association between diet and dependent variable, examine association between independent variable and diet as dependent variable, and examine effect of intervention

Question 25

best method for describing population’s diet intake?

Answer 25

24-hr recall (most accurate)

Question 26

best method for diet as independent on dependent variable (prospective and cross-sectional)

Answer 26

multi 24-hr recalls and FFQ

Question 27

best method for diet as dependent variable

Answer 27

similar for when diet is independent, but caution that differential response bias can be significant (independent variable is associated with other variables that affect dietary reporting error)

Question 28

best method for evaluating intervention effect on diet

Answer 28

biomarkers (if not feasible, then 24-hr recall)

Question 29

___ + ___ = estimate of intake of nutrients or food components of interest

Answer 29

food consumption data ; nutrient composition of food

Question 30

why care about measuring diet?

Answer 30

assess/monitor food and nutrient intake, formulate and evaluate gov health and ag policy, using data for commercial purposes, conduct epidemiological research, improve human health!

Question 31

purpose for measuring diet intake:

Answer 31

compare average nutrient intakes of diff groups, rank individuals within group, estimate individuals usual intake

Question 32

SDA automated multiple pass method 5 step approach:

Answer 32

1) quick list, purpose: collect list of foods and beverages consumed previous day
2) probe for foods forgotten
3) review/record time and eating occasion for each food/bev item
4) cycle through in detail, inquire about detailed description of food, amount, condiments, cooking methods, brands, other relevant info, review
5) final probe

Question 33

strengths of 24 hour recall?

Answer 33

short, inexpensive, easy to administer, can provide detailed info on types of food consumed, low respondent burden, used estimate nutrient intake of groups, multi recalls can be used to estimate nutrient intake in individuals, more objective than diet history, doesn’t alter usual diet, useful in clinical

Question 34

limitations of 24 hour recall?

Answer 34

seldom representative of usual intake, underreporting, relies on memory, omissions of dressings/sauces/beverages, data entry labour intensive

Question 35

two types of food records

Answer 35

weighed, estimated

Question 36

strengths of food records?

Answer 36

not depend on memory, provide detailed intake data, provide data about eating habits, multi day data more representative of usual intake, valid up to 5 days

Question 37

limitations of food records?

Answer 37

lots of work, response burden lead to low response rates, requires literacy, takes more time, reactivity, analysis is labour intensive and expensive, training required to increase reliability of measurements

Question 38

FFQ formats:

Answer 38

simple non-quantitative, semiquantitative (add portion sizes), quantitative (serving size relative to standard serving size)

Question 39

common FFQ questionnaires:

Answer 39

willed questionaire, block HHHQ, Diet History Questionnaire, NHANES

Question 40

what are the advantages of targeted FFQ “screeners” to normal FFQ?

Answer 40

do not require assess total diet, don’t always require quantitative accuracy, shorter (lower respondent burden)

Question 41

FFQ strengths?

Answer 41

can be self administered, machine readable, modest demand on respondents, relatively inexpensive for large sample, more representative of usual intake than few days of records, based on large population data, method of choice for research

Question 42

FFQ limitations?

Answer 42

not represent usual foods/portion sizes chosen by respondents, intake data compromised when multiple foods groups within single listings, depends on ability of subject to describe diet, requires memory, can be burdensome

Question 43

used to assess an individual’s usual diet intake over extended period of time

Answer 43

diet history

Question 44

traditional diet history:

Answer 44

1. collect general info about health habits
2. usual eating habits (24 hr recall)
3. cross check on data in step 2
4. complete 3 day food record

Question 45

examples of food related general health info:

Answer 45

number of meals per day (frequency of eating), dislikes, general appetite, barrier/symptoms to intake, use of nutrition supplements

Question 46

examples of lifestyle related general health info:

Answer 46

sleep/rest, work, physical activity, smoking, drugs, alcohol, finances

Question 47

strengths of diet hx:

Answer 47

assesses usual nutrient intake, can detect seasonal changes, data on all nutrients can be obtained, can correlate well with biochem measures

Question 48

limitations of diet hx

Answer 48

lengthy interview, highly trained interviewers, expensive and difficult to code, may overestimate nutrient intake, requires cooperative respondent with ability recall usual diet

Question 49

strengths of digital imaging?

Answer 49

good validity, takes less time than 24-hr recall or food records, respondent burden lower, acceptability to subjects, eating habits less affected by recording

Question 50

limitations of digital imaging:

Answer 50

large initial expense invovlved, periodic revalidation’s, unable distinguish visually similar foods or document prep methods, subject to technical probs