The Relationship between Breast-feeding and the Prevalence of Asthma Yousuke Takemura, MD, PhD Associate Professor Dept. of Family and Community Medicine.

The Relationship between The Relationship between Breast-feeding and Breast-feeding and

the Prevalence of Asthmathe Prevalence of Asthma

Yousuke Takemura, MD, PhDYousuke Takemura, MD, PhDAssociate ProfessorAssociate Professor

Dept. of Family and Community MedicineDept. of Family and Community MedicineMie University School of MedicineMie University School of Medicine

JapanJapan

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Yousuke Takemura,Yousuke Takemura, MD, PhDMD, PhDAssociate ProfessorAssociate ProfessorDepartment of Family and Community MeDepartment of Family and Community MedicinedicineMie University School of MedicineMie University School of Medicine2-174 Edobashi, 2-174 Edobashi, Tsu, Mie 514-8507Tsu, Mie 514-8507JAPANJAPANE-mail: E-mail: [email protected]

IntroductionIntroduction

There is growing evidence that asthma is becoming more common in the western countries.

Because treatment of asthma is somewhat difficult, prophylaxes have been sought.

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Many risk factors for asthma:Many risk factors for asthma:ageage, , gendergender, , parental smokingparental smoking, , and and family history of asthmafamily history of asthma

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Many studies on the role of breaMany studies on the role of breast-feeding in the prevention of chst-feeding in the prevention of childhood asthma:ildhood asthma:

1. 1. Positive associationPositive association2. 2. No associationNo association3. 3. Negative associationNegative association

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TABLE 1. The previous studies on the association betweenchildhood asthma and breast-feeding

Investigators N Agerange

Measurement ofbreast-feeding

Measurementof asthma

Negative associationSaarinen et al. 256 0-3 yr Feeding history

at clinicsWheezinghistory atclinics

Hide et al. 843 12 mo Questionnaire Questionnaire(asthma orbronchitis)

Raisler et al. 7,092 6 mo Questionnaire Questionnaire(cough orwheeze)

N: number of subjects, yr: year-old, mo: month-old

Investigators N Agerange

Measurement ofbreast-feeding

Measurement of asthma

No associationHalpern et al. 1,753 6 mo-

7 yrFeeding history atclinics

MD-diagnosed (asthma)

Gordon et al. 250 2 yr Feeding history atclinics

MD-diagnosed (eczema-asthma syndrome)

Golding et al. 13,135 5 yr Questionnaire Patients’ report (asthma)Fergusson et al. 1,110 4 yr Structured

interviewStructured interview (asthma)

Taylor et al. 13,135 -5 yr Questionnaire Structured interview (asthma)Midwinter et al. 457 5 yr Questionnaire Structured interview (asthma)Cogswell et al. 73 5 yr Diary MD-diagnosed (wheeze)Zeiger et al. 288 2 yr (Follow up study) MD-diagnosed (asthma)Lucas et al. 777 18 mo (Follow up study) MD-diagnosed (asthma or

wheeze)Gustaffson et al. 736 7 yr (Follow up study) Medical record review

(asthma)

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TABLE 1. The previous studies on the association betweenchildhood asthma and breast-feeding (continue)

Investigators N Agerange

Measurement ofbreast-feeding

Measurementof asthma

Positive associationMartin et al. 342 21 yr Questionnaire MD-

diagnosed(asthma)

Savilahti et al. 183 2 yr Feeding historyat clinics

Wheezehistory takenat clinic

N: number of subjects, yr: year-old, MD: physician

Many of these studies were based on relMany of these studies were based on relatively atively small sample populationsmall sample population, and , and did not adjust for confounding factorsdid not adjust for confounding factors s sufficiently. ufficiently. The present study examines the relationThe present study examines the relationship between breast-feeding and ‘ever hship between breast-feeding and ‘ever having asthma’ by aving asthma’ by population based casepopulation based case-control study-control study in Japan.in Japan.

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Materials and MethodsMaterials and Methods

Study PopulationStudy Population

33 public elementary schools (grades 1 – 6)33 public elementary schools (grades 1 – 6)15 public junior high schools (grades 1 – 3)15 public junior high schools (grades 1 – 3)

25,767 subjects25,767 subjects responded to the questionna responded to the questionnaire among 28,848 students.ire among 28,848 students.((the response rate = 89.3%the response rate = 89.3%))

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MeasurementMeasurement

the American Thoracic Society and Divisthe American Thoracic Society and Division of Lung Diseases, National Heart, Luion of Lung Diseases, National Heart, Lung, and Blood Institute (ATS-DLD) quesng, and Blood Institute (ATS-DLD) questionnairetionnaire for children (Japanese version)for children (Japanese version)

The reliability and validity of the ATS-DLD questionnaire to identify children with asthma has been well established. Y. Takemura et al.

Asthma: “yes” response to all of the following questions(1) Has your child ever had an attack of wheezing that has caused him/her to be short of breath? (2) Has your child had such an attack twice or more? (3) Has a physician ever informed you that your child has asthma? and (4) If so, at that time, did your child have shortness of breath with wheezing?

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Total: Total: 12,105 boys12,105 boys + + 11,723 girls11,723 girls, , aged 6 to 15 yrs aged 6 to 15 yrs

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Feeding patterns from the age of 1 to 3 monthFeeding patterns from the age of 1 to 3 monthss““breast-feeding onlybreast-feeding only”, “”, “mixedmixed”, or “”, or “artificial artificial feedingfeeding””

Parental smokingParental smoking: Having mother or father : Having mother or father who smoked one or more cigarettes per day who smoked one or more cigarettes per day Parental history of asthmaParental history of asthma: Subjects whose m: Subjects whose mother or father had ever been treated for asthother or father had ever been treated for asthmama

Statistical AnalysisStatistical Analysis

The characteristics of subjects with or withThe characteristics of subjects with or without asthma: out asthma: the chi-squared testthe chi-squared test or or Student’s t-testStudent’s t-testTo control for confounding factors such as To control for confounding factors such as age, gender, parental smoking, and parentage, gender, parental smoking, and parental history of asthma:al history of asthma: multiple logistic regression analysismultiple logistic regression analysis Dose-response relationship: Dose-response relationship: test of trendtest of trend Y. Takemura et al.

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ResultsResults

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Variables Asthma (%) Control (%) p value(n = 2,315) (n = 21,513)

Age (year-old) 10.71ｱ2.45 10.77ｱ2.53 0.30**Gender <0.01*** Male 1,429 (61.7) 10,676 (49.6) Female 886 (38.3) 10,837 (50.4)Parental smoking 0.14***

(+) 1,254 (54.2) 11,997 (55.8)(-) 1,061 (45.8) 9,516 (44.2)

Parental history of asthma <0.01***(+) 522 (22.6) 1,898 ( 8.8)(-) 1,793 (77.4) 19,615 (91.2)

Feeding pattern <0.01***Breast-feeding

only992 (42.9) 8,620 (40.1)

Mixed 966 (41.7) 9,134 (42.4) Artificialfeeding

357 (15.4) 3,759 (17.5)

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Variables Adjusted oddsratio

95% CI p value

Age1.000 0.986, 1.020 0.75

Gender Male 1.653 1.513, 1.808 <0.01 Female 1.000Parental smoking (+) 0.945 0.866, 1.032 0.21 ( - ) 1.000Parental history of Asthma (+) 3.028 2.714, 3.377 <0.01 ( - ) 1.000Feeding patterns Breast-feedingonly

1.198 1.054, 1.363 <0.01

Mixed 1.090 0.958, 1.239 0.19

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T A B L E 4 . T h e r e l a t i o n s h i p b e tw e e n f e e d i n g p a t t e r n s a n d p r e v a l e n c e o f a s th ma

F e e d i n g p a t t e r n s P r e v a l e n c e o f a s t h m a ( % )

B r e a s t - f e e d i n g o n l y 1 0 . 3 2 M i x e d 9 . 5 6 A r t i f i c i a l f e e d i n g 8 . 6 7

P f o r t r e n d < 0 . 0 1

DiscussionDiscussion

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The The mechanismmechanism of the unfavorable of the unfavorable effect of breast-feeding on asthmaeffect of breast-feeding on asthma

1. 1. Fat soluble chemicalsFat soluble chemicals accumulating in breast milk accumulating in breast milk 2. 2. Sensitization through Sensitization through breast milk breast milk

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Fat soluble chemicals in breast milk: If this mechanism is correct, children higher in the birth order would be more likely to have asthma. However, additional adjustment for birth order did not affect the association between asthma and breast feeding (adjusted odds ratio: 1.212; 95 percent confidence interval: 1.057, 1.389; p < 0.01).

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Sensitization through breast milk:Foreign protein antigens can be transmitted in breast milk. These antigens may provoke hypersensitivity. In fact, a study showed that this type of sensitization was seen in 10 percents of breast fed infants.

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AdvantageAdvantage

1. The 1. The large numberlarge number of subjects of subjects 2. Several aspects of 2. Several aspects of homogeneithomogeneityy 3. 3. AdjustmentAdjustment for confounding for confounding

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Limitation(1)Limitation(1)

Parental recallParental recall

Limitation(2)Limitation(2)

the small number of the referencethe small number of the reference

Although the reference is prefer to large nuAlthough the reference is prefer to large number, we used artificial milk users as the rember, we used artificial milk users as the reference since we would like to know the effeference since we would like to know the effects of ‘any exposure to breast-milk’ vs none cts of ‘any exposure to breast-milk’ vs none on the prevalence of asthma.on the prevalence of asthma.

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Limitation(3)Limitation(3)

duration of breast-feedingduration of breast-feeding

We used three months as cut-off point of dWe used three months as cut-off point of duration of breast-feeding since several stuuration of breast-feeding since several studies used three months as the criteria of thdies used three months as the criteria of the duration.e duration.

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ConclusionConclusion

Breast-feeding in infancy mighBreast-feeding in infancy might be related to the higher prevalent be related to the higher prevalence of asthma during pre-adolescence of asthma during pre-adolescence.ce.

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This study was published in This study was published in American Journal of Epidemiology American Journal of Epidemiology 2001;154(2):115-119.2001;154(2):115-119.