Determinants of cariogenicsnacking in adolescentsin Belfast and HelsinkiFreeman R, Heimonen H, Speedy P, Tuutti H. Determinants of cariogenicsnacking in adolescents in Belfast and Helsinki. Eur J Oral Sci 2000; 108: 504±510.# Eur J Oral Sci, 2000

The aim of the study was to investigate the determinants of reported snackconsumption in adolescents residing in Belfast, Northern Ireland and Helsinki,Finland. Ten % random samples of 14±15 yr old Belfast (n~628) and Helsinki(n~600) adolescents were obtained. A questionnaire assessed their demography,oral health knowledge, attitudes and the consumption of cariogenic snackscontaining non-milk extrinsic sugars (NMES). Five hundred and eighty-nine (94%)questionnaires were returned in Belfast and 441 (74%) questionnaires in Helsinki.Belfast adolescents had signi®cantly higher levels of oral health knowledge andhigher consumption rates for snacks containing NMES. The Helsinki adolescentshad more positive attitudes towards their oral health. Multivariant analysisshowed that demography was the most direct determinant of cariogenic snacking.The acquisition of oral health knowledge played a minor role. There is a need todevelop tailored and focused programmes to promote healthier snacking regimesin adolescents.

Ruth Freeman1, Harri Heimonen2,Patti Speedy1,3, Heikki Tuutti2

1Dental Public Health Research Group,School of Clinical Dentistry, The Queen'sUniversity of Belfast, Northern Ireland, UK,2Helsinki International Institute of Oral Health,Faculty of Medicine, University of Helsinki,Helsinki, Finland, 3Oral Health Promotion,Dental Department, Eastern Health and SocialServices Board, Belfast, Northern Ireland, UK

Dr. R. Freeman, Dental Public HealthResearch Group, School of Clinical Dentistry,The Queen's University of Belfast, RGH,Grosvenor Road, Belfast BT12 6BP,Northern Ireland, UK

Telefax: +44±28±90438861E-mail: r.freeman@qub.ac.uk

Key words: adolescence; dietary behaviours;oral health promotion

Accepted for publication September 2000

Over the past 30 yr the political con¯ict inNorthern Ireland has, according to OPPENHEIM

(1), resulted in the Province being recognised asbeing one of the most disadvantaged and deprivedregions in Europe. OPPENHEIM (1) has suggestedthat social unrest exacerbates the e�ects of socialdisadvantage and deprivation (gender, age, com-munity background, lack of education, unemploy-ment, poor housing and nutrition) upon health,resulting in increased morbidity. OPPENHEIM'S (1)view ®nds support in the dental caries prevalence ofthe children and adolescents resident in NorthernIreland. These children not only have the highestprevalence of dental caries in the United Kingdom(2±4), but also the consumption of snacks contain-ing non-milk extrinsic sugars (cariogenic snacking)is related to social disadvantage and deprivation(5, 6).

Other in¯uences upon health behaviours are saidto include health knowledge and attitudes (7).Previous research examining the role of knowledgeand attitudes has questioned the importance ofhealth knowledge (7) while implicating attitudes asa factor (8) in the adoption of healthier behaviours

by adolescents. The voluntary adoption ofhealthier behaviours has been associated withhealth-related attitudes (9) such as appearanceand self-regard (10). This suggested that healthknowledge may not be as important as oncethought in the determination of oral healthbehaviours.

It seemed that a schism existed in which onegroup of researchers suggested (1, 11) that demo-graphy in the guise of parental unemploymentstatus, age, gender and place of residence was theover-riding in¯uence, while other researchersdecried the role of demography and implicatedfactors speci®c to the individual (their healthknowledge, attitudes and beliefs) as determinantsof health behaviours (8±10). The question remainedwhat were the important in¯uences upon oralhealth actions and, more speci®cally, how diddemography and/or health knowledge and attitudesindividually or collectively determine the adoptionof oral health lifestyle habits in adolescence.

This is an important area of investigation, sincethere is a need to understand the competing rolesof demography, health knowledge and attitudes

Eur J Oral Sci 2000; 108: 504±510Printed in UK. All rights reserved

as determinants of cariogenic snacking in adoles-cence. If oral health promotion strategies are to bedeveloped to reduce caries prevalence and promotehealthier snacking in Northern Ireland, then it isnecessary to compare and contrast the demography(place of residence, age, gender and parentalemployment status), oral health knowledge andattitudes with a country which has a low cariesprevalence such as Finland (12).In order to gain a greater understanding of the

basis of cariogenic snacking in adolescence, thereis the need to use a methodology which will allowthe simultaneous examination of demography withoral health knowledge and attitudes in this regard.While acknowledging the place for single-act cri-terion (13) to explain health behaviours, its appro-priateness when studying more complex actionssuch as dietary behaviours has been questioned.It has been proposed (14) that when studyingbehaviours such as cariogenic snacking, it isnecessary to use a multiple-act criteria frameworkwhich has the potential to incorporate health know-ledge and attitudes with demography (gender, age,parental employment status and place of residence).In this way the role of demography, oral healthknowledge and attitudes can be examined asdeterminants of dietary behaviours in adolescence.The aim of this study was to investigate the role ofdemography, oral health knowledge and attitudesas determinants of cariogenic snacking in adoles-cents residing in Belfast, Northern Ireland andHelsinki, Finland, in order to discover the salientfactors in promoting healthier snacking.

Material and methods

Sample

A 10% sample of adolescents from Belfast in their4th year of post-primary education was obtainedusing the same sample frame provided by theBritish Association for the Study of CommunityDentistry, for their survey of 14-yr-old adolescents(2). Twenty schools from the Belfast area werecontacted and parents sent positive consent letters.Six hundred and twenty-eight pupils were invitedto take part. Although the same schools whichtook part in the survey (2) were included, theadolescents who completed the questionnaire werenot the same. The teachers were asked to give thequestionnaire to their pupils for completion duringtheir personal study time.The Finnish National Population Register

Centre obtained a valid 10% random sample ofadolescents in their 4th year of post-primaryeducation residing in Helsinki. Six hundred adoles-cents and their parents who resided in Helsinki

were contacted. The parents were sent a positiveconsent letter, which included a copy of thequestionnaire. The parents were asked to give thequestionnaire to their child for completion duringtheir homework study period.

Ethical approval for the study was given on theunderstanding that the adolescents and theirfamilies would be untraceable. This meant that itwas not possible to contact those adolescents whoseparent/guardian did not consent for them toparticipate in the investigation.

Questionnaire

The questionnaire was divided into four parts. The®rst part of the questionnaire inquired of thesubjects' gender, age, parental employment status,and city of residence.

The second part examined knowledge of thecauses of dental caries and periodontal diseaseand the e�ects of smoking upon the oral cavity. Inorder to ensure the scienti®c reliability of the ques-tions and answers, the report of the `Committee Onthe Medical Aspects of Food Policy on DietarySugars and Human Disease' (15) and the `Scienti®cBasis of Dental Health Education' (16) were usedto validate the questions and to identify the correctresponses for the prevention of dental caries. The`Scienti®c Basis of Dental Health Education' (16)was used to validate the questions and identify thecorrect responses for the prevention of periodontaldisease and LAMEY & LEWIS's `A Clinical Guide toOral Medicine' (17) was used for the questionon smoking and oral health.

Three questions assessed the adolescents' know-ledge about diet in the prevention of dental caries.The ®rst question asked `What is the main causeof tooth decay?' There were 5 options to thequestion. These were `not brushing properly',`eating too much sugar', `eating sugary foods anddrinks too often' (the correct option), `not goingto the dentist', and `weak enamel'. A secondquestion asked `How should you eat your sweets?'There were 2 responses `all at once' (correct option)or `slowly in small amounts during the day'. Thelast question asked `When is sugar most damagingto your teeth?' There were 5 possible responses(`at mealtimes', `in the morning after breakfast',`between meals' and `at bedtime' and `don't know').The 3 correct options were `in the morning afterbreakfast', `between meals' and `at bedtime' (16).A score of 1 was awarded for each correct option.This gave a range of scores from 0 (no correctanswers) to 5 (all answers correct) (16). This scoringallowed the division of the adolescents into twoprevention of caries knowledge groups: All thosewho scored 5 were designated as being correct

Factors in¯uencing adolescents' cariogenic snacking 505

compared with those who scored between 0 and 4,who were designated as being incorrect in theirknowledge of the prevention of dental caries.

The adolescents' periodontal health knowledgewas assessed by asking them `Which of the fol-lowing would you use to prevent your gums frombleeding?' There were 8 possible options of whichonly 4 were identi®ed as being correct (16). Thesewere `removing plaque', `brushing teeth', `usingdental ¯oss' and `using toothpaste'. Each timea correct answer was checked, a score of 1 wasawarded. This allowed a range of scores from 0 (nocorrect responses) to 4 (all correct responses). Thisallowed the division of the adolescents into twoperiodontal prevention knowledge groups. All thosewho scored 4 were designated as being correctcompared with those who scored between 0 and 3,who were designated as being incorrect in theirknowledge of the prevention of periodontal disease.

Finally the adolescents were asked `Which of thefollowing do you think are associated with smok-ing?' The options included `mouth ulcers', gumdisease', `tooth decay', `mouth cancer', `furredtongue', `bad breath' and `no e�ects'. The correctoptions were `mouth ulcers, gum disease, oralcancer, furred tongue, bad breath' (17). Each timea correct response was checked a score of 1 wasawarded. This allowed a range of scores from 0 (nocorrect responses) to 5 (all correct responses). Thisallowed the division of the adolescents into twosmoking and oral health knowledge groups:All those who scored 5 were designated as beingcorrect compared with those who scored between0 and 4, who were designated as being incorrect intheir knowledge of smoking and oral health.

The third section assessed oral health attitudes.The oral health attitudes were the adolescents'`opinion of their dental health', their `satisfactionwith the appearance of their teeth', their `wish tokeep teeth for life', their `concerns about the needfor dentures in the future', and, `taking responsi-bility for their own dental health'. These attitudinalquestions were assessed individually on a 5-pointLikert scale, ranging' from strongly disagree(scoring 1) to strongly agree (scoring 5).

A further question asked the adolescents `Whichof the following do you think are important reasonsfor looking after your teeth?' Scoring 1 for `yes' or0 for `no', the responses included `to be attractiveto others', `for my teeth to look nice', `to avoid falseteeth', `I like my breath to smell fresh', `to avoidtoothache', `to avoid dental treatment', and `I likemy mouth to feel fresh'.

All the scores for the reasons for caring forteeth were subjected to a principal componentsfactor analysis using a varimax orthogonal rotationprocedure. Two factors were extracted (adopting

the convention of accepting factors with greaterthan unitary eigenvalues) (18). The ®rst factor wascomposed of `to avoid false teeth', `to avoid tooth-ache' and `to avoid dental treatment', havingan eigenvalue of 2.59. It explained 43% of thevariance. A second factor, with an eigenvalue of2.58, was composed of `teeth looking nice', `freshbreath', `looking attractive' and `fresh mouth'. Thisexplained 43% of the variance. These two factorsdescribed, ®rst, health reasons (avoiding dentures,toothache and dental treatment) directed towardsmaintaining their physical dental health (health-directed; Factor 1) and, secondly, psycho-socialreasons related (feeling and looking good) tomaintaining their physical dental health (health-related; Factor 2). The health-directed scalepossessed a Cronbach alpha coe�cient of 0.90,and the health-related scale possessed a Cronbachalpha coe�cient of 0.94. This demonstrated a goodinternal consistency to allow for group compar-isons. The range of scores for the health-directedfactor scale was between 0 (no reasons checked) to 3(all reasons checked). The range of scores forthe health-related factor scale was between 0 (noreasons checked) to 4 (all reasons checked).

Finally, the adolescents were asked to identifythe type and report the frequency of the snacksthey ate to assess their consumption. A snackcheck-list included foods and drinks, which con-tained non-milk extrinsic sugars (NMES) (15) suchas chocolate and confectionery, cakes and biscuits,hot drinks with sugar, fruit juice, fruit squashwith sugar and carbonated (®zzy) drinks withsugar. The frequency of cariogenic snacking wasassessed on a 6-point scale ranging from neversnacking (scoring 0) to several times a day(scoring 6). Using the same methodology asdescribed by AÊ STRùM (19), all foods and drinkscontaining NMES were combined together to forma total cariogenic snacking score (19). This rangedfrom 0 (no NMES containing snacks eaten) to 36(all NMES snacks consumed several times a day).The total cariogenic snacking scale possessedCronbach alpha coe�cient of 0.61 which accordingto NUNNALLY (20) is reasonable to allow for groupcomparisons.

The questionnaires were posted to the schoolsinvolved and administered to the pupils in Belfastby their teachers during their personal study period.In Helsinki, the adolescents were requested tocomplete the questionnaire sent to their homesduring their homework study period. Parents andteachers were instructed not to provide anyassistance with the completion of the questionnaire.The completed questionnaires were returned to theresearchers in Belfast and Helsinki in the pre-paidenvelopes provided.

506 Freeman et al.

Statistical analysis

Each questionnaire was coded prior to entry ontoa PC computer. The data was entered ontoSPSS.PC+ and subjected to the following statist-ical analysis: chi-square analysis, t-tests andstepwise regression analysis.

Results

Six hundred and twenty-eight questionnaires weresent to schools in Belfast. Five hundred andeighty-nine questionnaires were returned giving aresponse rate of 94%. Six hundred questionnaireswere sent to the homes of adolescents in Helsinki.Four hundred and forty-one were returned givinga response rate of 74%.The ages of the adolescents for the entire sample

ranged from 14±16 yr with the majority of theadolescents (62%) aged 15 yr old. The mean age ofthe Belfast adolescents was 14.75 (¡0.46) and forthe Helsinki adolescents 14.62 (¡0.62). Equivalentproportions of adolescents in Belfast (57%) andHelsinki (55%) were female (w2~0.59; P>0.05).Fourteen % (136) of the total sample of adolescentshad parents who were unemployed. Greater pro-portions of adolescents in Belfast (21%) comparedwith those in Helsinki (6%) stated that theirparent(s) were unemployed (w2~41.94; P50.001).Only 4 adolescents gave completely correct

answers to all of the questions on how to preventdental caries and periodontal disease. One hundredand seventy-six (17%) adolescents answered thequestion about smoking and oral health correctly.Twenty-®ve % (257) o�ered completely incorrectanswers about the prevention of periodontaldisease, and 7% (72) gave completely incorrectanswers about the prevention of dental caries.Signi®cantly larger proportions of adolescentsresiding in Belfast (5%) compared with thosein Helsinki (1%) gave completely correct answerson the prevention of dental caries (w2~12.35;P<0.001). Similarly for the prevention of perio-dontal disease (Belfast, 12% :Helsinki, 5%;

w2~18.06; P<0.001) and smoking and oral health(Belfast, 23% :Helsinki, 9%; w2~38.87; P<0.001),signi®cantly larger proportions of Belfast adoles-cents o�ered completely correct responses comparedwith those from Helsinki.

For all of the 1030 adolescents the mean score for`opinion of their dental health' was 3.51 (¡0.92),`feeling responsible for their own dental health'was 4.20 (¡0.88), `concerns about the need fordentures' was 4.15 (¡1.12), the wish `to retain alltheir teeth for life' was 2.70 (¡1.05) and `beingsatis®ed with the appearance of their teeth' was3.63 (¡0.96). When Helsinki and Belfast adoles-cents were compared, the Belfast adolescents hadsigni®cantly lower mean scores for the attitudes`opinion of their dental health', `being responsiblefor their own dental health', and `concerns aboutthe need for dentures' (Table 1). This reliable dif-ference was only moderate in the mean scores for`opinion of teeth' (5% di�erence between Helsinkiand Belfast mean scores), `concerns about the needfor dentures' (6% di�erence in Helsinki and Belfastmean scores), and being `responsible for their owndental health' (4% di�erence between Helsinki andBelfast mean scores).

The mean scores for health-directed reasons forcaring for teeth was 2.53 (¡0.66) for all of theadolescents in the sample. The mean score forhealth-related reasons for caring for teeth was 3.80(¡1.15). The Belfast compared with the Helsinkiadolescents had signi®cantly higher mean scores forthe health-directed and health-related reasons forcaring for teeth (Table 1). Although the di�erencesin mean scores between Helsinki and Belfast weresmall, they nevertheless represented a di�erenceof 11% for health-directed reasons and 10% forhealth-related reasons for caring for teeth. In viewof this it is reasonable to suggest that these ®ndingsrepresent a meaningful di�erence in mean scoresbetween Helsinki and Belfast.

Twenty-seven % (n~278) of the entire popula-tion of adolescents reported that they consumedchocolate and confectionery several times a day.Twenty-®ve % (n~258) stated that they drank

Table 1

Oral health attitudes: comparisons between Belfast and Helsinki

Oral health attitudeBelfast adolescents(n~589)6(SD)

Helsinki adolescents(n~441)6(SD) t P

Satisfaction with appearance 3.60 (0.95) 3.68 (0.97) 1.59 0.11Opinion of health teeth and gums 3.41 (0.86) 3.65 (0.86) 4.08 50.001Responsible for own dental health 4.14 (0.89) 4.34 (0.86) 3.60 50.001Normal to lose teeth with age 2.64 (1.05) 2.73 (1.05) ÿ1.38 0.18Concerns about needing dentures 4.03 (1.19) 4.93 (1.00) 4.08 50.001Health-directed reasons 2.67 (0.60) 2.34 (0.70) ÿ8.08 50.001Health-related reasons 3.60 (1.16) 4.00 (1.13) 2.79 0.005

Factors in¯uencing adolescents' cariogenic snacking 507

carbonated drinks with sugar, with slightly lowerproportions of adolescents admitting to consumingcakes (16%), hot drinks with sugar (17%) and fruitsquashes (15%) several times a day. Signi®cantlylarger proportions of adolescents from Belfastcompared with Helsinki stated that they consumedcariogenic snacks several times a day (Table 2).Belfast adolescents had signi®cantly higher meanscores (29.95¡4.64) for total reported cariogenicsnacking compared with those from Helsinki(19.52¡4.10) (t~19.87; P50.001).

Hierarchical multiple regression was adopted toexplain the variance in adolescent cariogenic snack-ing (operationalised by self-reported consumptionof snacks containing NMES). The independentvariables were introduced in three blocks. The ®rstblock consisted of demographic variables (parentalemployment status, gender and city of residence)de®ned by 3 dummy variables with the Belfastsample, parental unemployment, and female sub-ject acting as baseline. This block acted as a controlto remove demographic variance, and was forced

into the equation as a ®rst step. The second blockconsisted of health-directed and health-relatedreasons for caring for teeth. The attitudes `opinionof oral health', `responsibility for their own oralhealth', and `concerns about the need for dentures'were also included. The ®nal block was introducedto test for the remaining e�ect of the adolescents'oral health knowledge once demographics and oralhealth attitudes had been controlled for. Of thethree oral health education variables, only knowl-edge of smoking and oral health were able toexplain any additional variance of reported con-sumption of cariogenic snacks. The complete modelexplained over a third of the variance (36%) ofcariogenic snacking in the adolescents studied(Table 3).

Discussion

Adolescents in Northern Ireland have been identi-®ed as having the highest prevalence of dental

Table 2

Comparisons between Belfast and Helsinki adolescents daily frequency of cariogenic snacks consumed

Foods and drinks consumedat least daily

Belfast adolescents(n=589) n (%)

Helsinki adolescents(n=441) n (%) w2 P

Chocolate and confectionery 169 (70) 25 (30) 273.37 <0.001Cakes and biscuits 157 (98) 3 (2) 495.82 <0.001Hot drinks with sugar 64 (83) 33 (17) 98.91 <0.001Carbonated (®zzy) drinks with sugar 222 (88) 31 (12) 228.46 <0.001Fruit squash with sugar 107 (70) 45 (30) 79.92 <0.001Pure fruit juice 114 (51) 109 (49) 29.48 <0.001

Table 3

Multiple linear regression summary results of predicting the reported consumption of snacks containing non-milk extrinsic sugars inBelfast and Helsinki adolescents

B se t P DF DP

Constant 23.00{ 0.79 23.32 <0.001

Model 1: Demographya 186.10 <0.001Parental employment status ÿ1.20 0.29 ÿ4.18 <0.001Gender 1.45 0.25 5.80 <0.001City of residence ÿ5.37 0.28 ÿ19.39 <0.001

Model 2: Oral health attitudes (including reasons for caring for teeth) 112.83 <0.001Opinion of oral healthb ÿ0.41 0.14 ÿ3.02 0.003Oral health-related reasonsc 0.27 0.11 2.48 0.01

Model 3: Oral health knowledge 47.94 <0.001Smoking knowledged ÿ0.23 0.11 ÿ2.06 0.04

R Square~0.36, F(9, 1018)~64.89, P<0.001.{Only signi®cant values presented in Table 4.a0~parental unemployment, 1~parental employment. 0~female, 1~male. 0~Belfast, 1~Helsinki.bFive item scale, higher score denotes positive opinion of oral health.cFive item scale, higher score denotes positive health-related reasons.dHigh scores denotes greater knowledge about smoking and oral health.

508 Freeman et al.

caries in the UK (2±4). This has been related topoverty and deprivation, which has been exacer-bated by the political unrest over the past 30 yr (1).The aim of the work presented here was toinvestigate the role of demography, oral healthknowledge, and attitudes as determinants in cario-genic snacking in adolescents residing in Belfast,Northern Ireland and to compare them with anequivalent group in Helsinki, Finland, in order todiscover the salient factors involved in promotinghealthier snacking.With regard to the four aspects of demography

examined, greater proportions of parents in Belfastwere said to be unemployed compared withHelsinki. This was perhaps to be expected as theNorth and West of Belfast is considered to havethe highest social deprivation in Europe (19). Interms of their age and gender, the adolescentswere similar.The adolescents in Belfast had greater know-

ledge about the prevention of dental caries, perio-dontal disease and the e�ects of smoking uponthe oral mucosa, but had less positive attitudestowards their dental health. Although the dif-ferences were fairly small in mean attitude scores,reliable di�erences did exist between the two groups.The Helsinki adolescents consistently scored higherthan the Belfast adolescents for all 5 of the oralhealth attitudes, while the Belfast adolescentsscored 11% higher for health-directed and 10%higher for health-related reasons for caring for teeth.Nevertheless, despite the Belfast adolescents beingmore aware of the link between diet and dentaldecay, their wish to avoid dental disease andtreatment, and to look and feel good (9), theystill indulged in unhealthy snacking. Helsinkiadolescents had healthier snacking regimes despiteknowing less about the prevention of oral diseases.The prediction of cariogenic snacking in the

adolescents may provide the answer as to whythe Belfast adolescents maintained this unhealthylifestyle habit. Thirty-six % of the variance wasexplained by demography, oral health attitudes(including reasons for caring for teeth), and oralhealth knowledge. Thirty-®ve % of the variancewas explained by demographic factors, with oralhealth attitudes and reasons for caring for teethproviding an additional 0.7%. Only 0.3% of thevariance in cariogenic snacking was explainedby oral health knowledge, when demographicsand oral health attitudes had been controlled for.It would seem that demography (parental employ-ment status, city of residence and gender) was themost direct determinant of cariogenic snacking inadolescents who completed the questionnaire. Theiroral health attitudes (including reasons for caringfor teeth) and knowledge played a minor role.

NETTLETON & BUNTON (22), in their critique ofhealth promotion, have proposed that individualswho are `structurally disadvantaged', as thoseadolescents in Belfast, are unable to take advantageof their increased knowledge and health-relatedattitudes to change from less to more healthylifestyle behaviours. Their social deprivation wouldlimit their ability to act and voluntarily adopthealthier habits. NETTLETON & BUNTON (22) sug-gested that health promotion, which ignores thein¯uence of structural and social disadvantageupon health and lifestyle, `exacerbates existinghealth inequalities'. It would seem that when oralhealth education is promoted at the expense of otherstrategies in deprived communities to improve oralhealth, then inequalities not only remain but may beintensi®ed.

Considering that the Helsinki adolescents hadmore healthy snacking behaviours than theirBelfast counterparts, what lessons can be learnt topromote healthier snacking in adolescents residentin Northern Ireland? The need to put in placehealthy public policies, as those developed inFinland, to promote oral health must be supported.These have included the recognition by theMINISTRY OF SOCIAL AFFAIRS AND HEALTH of thee�ects of social disadvantage and deprivation uponoral health behaviours, the identi®cation ofnational targets for oral health, and the emphasisof school-based oral health promotion programmes(23, 24). The need to introduce school-basedprogrammes to promote empowerment and self-reliance has according to HONKALA (24) resulted inshifts in Finnish adolescents from less to morehealthy oral health behaviours as re¯ected in the®ndings of this study.

While the ®ndings of this study suggest the needin Northern Ireland to change from relying uponan educational model of health promotion (7) toone which incorporates and recognises the role ofdemography upon the voluntary adoption of healthbehaviours (11), it is necessary to acknowledge itslimitations. These are related to the method ofadministration of the questionnaire. Althoughevery precaution was undertaken to ensure thatneither parent or teacher assist in the completion ofthe questionnaire, it must be acknowledged thatthis is a possible source of experimental error withmailed questionnaires (25). Another disadvantageis identifying the respondents who drop out. Inthis study, due to restrictions of the ethicalcommittee, it was not possible to identify thoseadolescents who did not return their question-naires. However it has been suggested by DILLMAN

(26) that response rates in the order of 75%are appropriate when studying homogeneouspopulations in this manner.

Factors in¯uencing adolescents' cariogenic snacking 509

It is within these limitations that the followingconclusions are made. Health promotion policieswhich focus upon the acquisition of knowledgetend to be ine�ective in deprived communities asthe individual may not have the ability or power tochange (11, 22). There is the need to acknowledgethe con¯icting roles of demography, oral healthknowledge, and attitudes upon the cariogenicsnacking behaviours of adolescents. Programmestailored to address social deprivation and dis-advantage (23, 24) must be developed in NorthernIreland so that adolescents may use the informationavailable to them to act upon their positive health-related attitudes and so adopt healthier snackingregimes. By doing so, the promotion of healthiersnacking may be a reality for adolescents resident inBelfast, Northern Ireland.

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