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The impact of recall bias on the accuracy of dietary information

Thesis (MNutr)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Background: A number of observational studies where information was obtained
retrospectively have been used in the past to inform guidelines regarding allergy prevention.
Studies looking at the causative/protective properties of infant dietary factors on diseases
that occur later in life also rely on maternal recall many years later. It is unclear however
what the effect of the recall bias was on the accuracy/quality of the information obtained.
Objectives: The aim of the study was to determine the impact of recall bias 10 years
retrospectively on the accuracy of dietary information in relation to breast feeding, weaning
age and introduction of allergenic foods. A literature review was performed into studies
assessing the accuracy of data obtained retrospectively and into studies using retrospective
data to draw conclusions on the protective/causative factors of infant feeding in relation to
food allergy.
Methodology: An infant feeding questionnaire was developed from some of the same
questions that were asked by mothers recruited into the FAIR study, a prospective birth
cohort on the Isle of Wight. Families had been recruited and followed up since 2001/2002
and data has been gathered when the mothers were 36 weeks pregnant, and then when
their child was 3, 6, 9 months and 1 and 2 years old. Mothers were asked in 2012, when their
children were 10 years of age, to complete this questionnaire. Agreement of answers was
computed using Kappa coefficients, Spearman’s correlation and percentage agreement. Results: One hundred and twenty five mothers completed the questionnaire. There was
substantial agreement for recall of whether mothers breast fed, the duration of EBF and
breast feeding 10 years earlier (k = 0.79, r = 0.70 and r = 0.84 respectively). Seven per cent
(n = 9) of mothers however who did breast feed reported not to have. Eighty four per cent (n
= 103) of mothers recorded correctly whether their child had a bottle of formula milk in
hospital. Ninety four per cent (n = 116) of mothers recalled accurately that their child had
received formula milk at some stage of their infancy. The exact age at which formula milk
was first given to their child was answered accurately (r = 0.63). The brand of formula milk
provided was poorly recalled. Answers to when mothers first introduced solid foods into their child’s diet were not accurate (r = 0.16). The age of introduction of peanuts was the
only food allergen that mothers recalled accurately for when they first introduced this into
their child’s diet (86% correct answers). Recall of whether peanuts were consumed during
pregnancy was accurate after two years (k = 0.64) but not after 8 years (k = 0.39).
Conclusion: The study highlights the importance of possible recall bias of infant feeding
practices by mothers over a period of 10 years. Recall related to breast feeding and formula
feeding were accurately recorded for, but not for age of introduction of solid foods and
introduction of allergenic foods. Studies relying on maternal recall of weaning questions
need to be cautious. / AFRIKAANSE OPSOMMING: Agtergrond: ’n Aantal waarnemingstudies waarin inligting op retrospektiewe wyse of
terugwerkend bekom is, is in die verlede gebruik om riglyne oor die voorkoming van allergie
neer te lê. Studies oor die veroorsakende/beskermende kenmerke wat
kindervoedingsfaktore op latere siektes het, steun verder op die herinneringe wat die
moeder baie jare later kan oproep. Dit is egter onduidelik watter uitwerking hierdie
oproepvooroordeel op die akkuraatheid/gehalte van die versamelde inligting het.
Oogmerke: Die oogmerk met die studie was om die impak te bepaal wat oproepvooroordeel
met terugwerkende effek van 10 jaar op die akkuraatheid van voedingsinligting oor
borsvoeding, speenouderdom en die insluiting van allergeniese voedselsoorte uitoefen. ’n
Literatuuroorsig was onderneem van studies wat die akkuraatheid evalueer van data wat
retrospektief bekom is, asook studies wat retrospektiewe data gebruik om gevolgtrekkings
oor die beskermende/veroorsakende kenmerke van kindervoeding met betrekking tot
voedselallergie te maak.
Metodologie: ’n Kindervoedingsvraelys is saamgestel vanaf sommige van die vrae wat aan
gewerfde moeders voorheen in die FAIR-studie, ’n voornemende geboortekohort op die
eiland Wight, gestel is. Gesinne is in 2001/2002 gewerf en opgevolg, en data is versamel toe
die moeders 36 weke swanger was; en weer toe hulle kinders die ouderdom van 3, 6, 9
maande en 1 en 2 jaar bereik het. In 2012, toe hulle kinders 10 jaar oud was, is die moeders
weer versoek om hierdie vraelys in te vul. Ooreenstemming tussen antwoorde is bepaal deur
Kappa koeffisiënte, Spearman korrelasies en persentasie ooreenstemming. Resultate: Eenhonderd vyf-en-twintig moeders het die vraelys ingevul. Daar was beduidende
ooreenkoms in die moeders se oproep oor die vraag of hulle borsvoeding gegee het, hoe
lank eksklusiewe borsvoeding (EBV) geduur het, asook borsvoeding 10 jaar vantevore (k =
0.79, r = 0.70 en r = 0.84 onderskeidelik). Sewe persent (n = 9) van die moeders wat wel
borsvoeding gegee het, het egter geantwoord dat hulle dit nie gegee het nie. Vier-en-tagtig
persent (n = 103) van die moeders het akkuraat geantwoord op die vraag of hulle kinders
bottelvoeding met ’n melkformule in die hospitaal ontvang het. Vier-en-negentig persent (n =116) van die moeders kon akkuraat oproep dat hulle kinders in ’n sekere stadium van hulle
kindertyd melkformule ontvang het. Die vraag oor presies hoe oud die kinders was toe hulle
die eerste maal melkformule ontvang het, is akkuraat beantwoord (r = 0.63). Die
handelsnaam van die melkformule kon nie goed herroep word nie. Antwoorde oor wanneer
moeders die eerste maal vaste voedsel by hulle kinders se dieet ingesluit het, was nie baie
akkuraat nie (r = 0.16). Die ouderdom waarop grondboontjies ingesluit is, was die enigste
antwoord wat moeders akkuraat kon oproep (86% korrekte antwoorde) op die vraag
wanneer hulle die eerste maal ’n voedselallergeen by hulle kinders se dieet ingesluit het. Die
antwoord op die vraag of hulle tydens hul swangerskap grondboontjies geëet het, was
akkuraat na twee jaar (k = 0.64), maar nie na agt jaar (k = 0.39) nie.
Gevolgtrekking: Die studie onderstreep die belang van moontlike oproepvooroordeel
rakende kindervoedingspraktyke by moeders oor ’n tydperk van 10 jaar. Die oproep oor
borsvoeding en formulevoeding is korrek aangedui, maar nie vir die ouderdom waarop vaste
voedselsoorte en allergeniese voedselsoorte ingesluit is nie. Studies wat op moederoproep
oor speningsvrae staatmaak, moet omsigtig gedoen word.

Identiferoai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86429
Date04 1900
CreatorsVan Zyl, Zoe
ContributorsVenter, Carina, Blaauw, Renee, Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Interdisciplinary Health Sciences. Division of Human Nutrition.
PublisherStellenbosch : Stellenbosch University
Source SetsSouth African National ETD Portal
Languageen_ZA
Detected LanguageUnknown
TypeThesis
Format1 v. (various pagings)
RightsStellenbosch University

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