British ]ournal of Dermatology 1997; 136: 498-501 .

Predictors of atopic dermatitis in Leicester children

J.BERTH-JONES, S.GEORGE AND R.A.C.GRAHAM-BROWNDepartment of Dermatology. Leicester Royal Infirmary. Leicester LEI 5WW. U.K.

Accepted for publication 9 September 1996

Summary There is little contemporary data available on the prevalence of atopic dermatitis (AD) or the riskfactors associated with this disease. We therefore performed a prospective study of 1-year-oId childrenbased on a cohort of consecutive births in Leicester hospitals.

Parents of 1800 children born between March and May 1992 were asked at the time of the birth toallow their child to be entered on a register. A sample of 499 of these children were invited forinterview and examination at 1 year of age. Data were collected on gestational maturity, birthweight, feeding pattern, family history of eczema and atopy, social class and other parameters.

Eour hundred and thirteen of the 499 children were examined (83%). The overall point prevalenceof AD was 10-7% (95% confidence interval, 7-7%-13-7%). The most significant risk factor for achild developing AD was a parental history of eczema.

The available evidence indicates that atopic dermatitis(AD) has increased in prevalence in recent years. ̂A community-based study undertaken among childrenaged 1-4 years, in Leicester, showed an overall pointprevalence of 14-0% (95% confidence interval (Cl),10-2%-17-8%).^ It is therefore not surprising thatthis disease accounts for 6% of referrals to ourdepartment.^ However, there are still insufficient con-temporary prevalence data from the U.K., based onexamination, by a dermatologist, of a prospectivelydefined population.

We have undertaken a prevalence study based on acohort of consecutive births in Leicester hospitals inorder, primarily, to provide a further estimate of theprevalence of the disease in the community and, secondly,to provide further data on a number of possible riskfactors including family history of atopic illness,'*"^ mater-nal age,^ birth weight,^'' gestational maturity,'' breastfeeding pattern^'^ and social class.^ We examined somefactors which may infiuence exposure to house dust mite,such as the use of central heating and the frequency ofdusting and vacuuming. Possible ethnic differences werealso examined and these are published separately. ̂ °

Methods

Birth registration, interview and examination

A register of consecutive live births was compiled in thetwo major Leicester obstetric units and a sample was

Correspondence: Dr Berth-Jones, Department of Dermatology, WalsgraveHospital, Coventry CV2 2DX, U.K.

drawn, interviewed and examined at 1 year of age asdescribed elsewhere. ̂ ° A structured questionnaire wasused to record data on possible risk factors.

Enquiry was made regarding the medical history ofthe child and family, with particular emphasis on atopicillness. Other data recorded included ethnic origin, socialclass, feeding pattern and diet. Each child was classifiedinto one of four groups according to whether the breastfeeding pattern adopted during the first 4 months wasbest described as 'not breast fed at all', 'breast fed inter-mittently with regular bottle feeds', 'breast fed regularlywith occasional bottle feeds' or 'exclusively breastfed'. The total duration of breast feeding was alsorecorded. Enquiry into environmental factors at homeincluded whether central heating was fitted, and theaverage intervals at which dusting and vacuumingwere performed.

For children who had suffered from a rash, systematicenquiry was made into the history, aggravating factorsand sources from which advice had been sought, asdetailed elsewhere.^° Every child was examined. Ifeczema was present, details of the distribution andseverity were recorded. Criteria for diagnosis of ADand assessment of severity have also been describedelsewhere.^°"^'^ The study was approved by the Leices-ter Research Ethics Committee.

Results

Demographic data

One thousand and eight hundred births took place

498 © 1997 British Association of Dermatologists

PREDICTING ATOPIC DERMATITIS 499

Table 1. Family history of atopic illness. Comparison of subjects withand without diagnosis of atopic dermatitis

Eczema

MotherFatherSiblingAny first

degree relativeAny relative

AsthmaMotherFatherSiblingAny first

degree relativeAny relative

Hay fever

MotherFatherSiblingAny first

degree relativeAny relative

All atopic disease

MotherFatherSiblingAny first

degree relativeAny relative

Atopic dermatitis (%)(11 = 44)

13 (30)11(25)8(18)

24(55)25(57)

3(7)3(7)4(9)

9(21)20 (46)

7(16)7(16)2(5)

16(36)21 (48)

16(36)18(41)10(23)

32 (73)35 (80)

Normal (%)(n = 369)

48 (13)14(4)44(12)

93 (25)122 (33)

27(7-3)28(8)39(11)

87(24)149 (40)

63(17)58 (16)16(4)

123(33)159 (43)

107(29)78(21)77(21)

200 (54)262 (71)

P(chi~ test)

0-007<0-00001

0-34

0-000090-003

NSNSNS

NSNS

NSNSNS

NSNS

NS0-006

NS

0-029NS

NS, not significant.

during the period of registration, which extended from30 March 1992 until 31 May 1992. In only 13 caseswas permission for registration refused. A further eightchildren who were adopted or died during the perinatalperiod were excluded. The register therefore contained1779 births.

One year later, a sample of 499 of the registeredchildren were sent appointments. Sixty-five had movedaway from Leicester, three had died and further parti-cipation was refused in eight. In 10 cases no contactcould be established. Therefore, 413 children wereexamined and the parents interviewed. The mean andmedian ages were 58 and 57 weeks, respectively.

Prevalence and severity of atopic dermatitis

Atopic dermatitis was diagnosed in a total of 44children - an overall point prevalence of 10-7% (95%

CI, 7-7%-13-7%). The prevalence values were 10-4%in males and 11-0% in females, a difference of 0-6%(95% CI, -5-4% to 6-6%).

In addition to these cases where AD was present onthe date of examination, there was a history compatiblewith AD in 20 children. The cumulative incidence cantherefore be estimated at 15-5% (95% CI, 12-0%-19-0%).

The severity of the AD was low. The mean sign(SASSAD) score was 7 (n = 44; range, 1-16; standarddeviation (SD), 3-6). The overall severity grades weremild in 36 (82%) and moderate in eight (18%).

Possible risk factors

There was a positive family history of at least one atopicdisease in at least one relative in 297 (72%) of thesample. Breakdown of these data into individual atopicdiseases is shown in Table 1. A positive family history ofeczema was significantly more common in mothers,fathers, all first degree relatives and all relatives ofsubjects with AD, than those without. In contrast,neither asthma nor hay fever was significantly morecommon in any group of relations.

The mean maternal age at time of delivery was 27-0years {n - 413; SD, 4-9). Mothers of children who laterdeveloped AD had a mean age of 26-9 (n - 44; SD, 4-8)and the others 27-0 (n = 369; SD, 5-0). This differencewas not statistically significant.

There were no significant differences in birth weightor gestational maturity between those children whodeveloped AD and those who did not. The mean birthweights were 3-4 kg (SD, 0-39) in those children whodeveloped AD, and 3-2 (SD, 0-56) in those who did not.Those children who developed AD were born at 3 - 3 days(SD, 8-9) post-term, and those who did not were born at4-3 days (SD, 13-1) post-term.

When children who developed AD were comparedwith the others they were slightly more likely to havebeen breast fed (66% vs. 57%). Of those who were breastfed, children with AD had been breast fed for slightlylonger than those without AD (6-2 vs. 5-7 months, notstatistically significant), but the proportion who receivedexclusive breast feeding was lower among those withAD (28% vs. 46%, P = 0.10, chi-squared). Vegetariandiets were adopted for 49 children, including seven ofthose with AD. This did not appear to influence therisk of developing AD.

There was an apparent tendency for AD to sparechildren born to families where the head of the house-hold was not employed. Only 4% of children born insuch households developed AD. The prevalence of AD

I 1997 British Association of Dermatologists. British Journal of Dermatology, 136. 498-501

500 J. BERTH-JONES et al.

did not otherwise seem to be affected by social class, butdifferences would have to have been very large to bedetected given the sample size examined.

Central heating was fitted in the vast majority 360(87%) of the 413 households in the sample; 82% ofhouseholds of children with AD and 88% of householdsof children without AD. There was no significant differ-ence between AD sufferers and non-sufferers.

Mean dusting and vacuuming intervals were 2 '9 (SD.2'7) and 1-8 days (SD, 1-6), respectively, in householdsof atopies and 4-0 (SD, 5-6) and 2'2 (SD, 2-4) inother households. These differences are not statisticallysignificant.

Discussion

The overall point prevalence of AD in this study, 10-7%,was high relative to earlier studies,^^"^^ although com-parable with more recent data from England^^ andScotland.^'' In view of the high prevalence found inthis study it is important to examine possible sources ofbias in the sample. It is possible that those parentsrefusing to allow examination of their child lackedinterest because their children had normal skin. How-ever, these were such a small proportion of the samplethat any resultant error would be minimal. It is alsopossible that bias was introduced by those subjects whohad moved away from the city, but we have no reason tosuppose that those with a child affected by AD would bemore or less likely to move.

We therefore believe this estimate to be representativeof the prevalence of AD, in children of this age, in thecity of Leicester. Considerable caution is required if theresults are to be extrapolated to a wider population.There may be geographical variation in the prevalenceof AD within the U.K.̂ Leicester is an affluent industrialcity and it is possible that urban populations are morevulnerable to atopic disease than rural populations.^This hypothesis is supported by the demonstration ofa higher prevalence of positive prick tests in thosedwelling in an urban environment in the U.S.A.̂ ^

Comparisons between different prevalence studiesare fraught with difficulty since different methodologiesmay produce divergent results.^ However, consideringthe confidence intervals and the difference in age groupsampled, this result seems compatible with a previousrecent estimate from a community-based survey ofLeicester children aged 1-4 years, in which the overallpoint prevalence, based on examination of the children,was 14-0%.^ These data support the hypothesis thatthe prevalence of AD is increasing.^

In this study we have obtained information on anumber of environmental and biological factors whichpreviously have been suggested to infiuence the risk ofAD.*~^ Our data do not indicate any strong relationshipbetween the risk of AD and sex, maternal age, birthweight, gestational age, breast feeding pattern, vegetariandiet or central heating. Weak relationships with thesefactors cannot be excluded without examining a largersample.

Our finding that a family history of eczema representsa strong risk factor for the development of AD in a childwas anticipated. It is perhaps more surprising thatneither asthma nor hay fever in relatives appeared toincrease the risk of developing AD. This apparent lackof association of AD with a family history of asthmacontrasts with the findings in a large national birthcohort study, ̂ although other investigators have noteda similar tendency for specificity in the inheritance ofatopic diseases.'^'^^'^^ The risk appeared greater tochildren of fathers than of mothers with eczema. Thesedata would therefore appear to conflict with previousreports suggesting that maternal atopy carries a greaterrisk of inheritance of atopy^^ and AD.̂ ^

Acknowledgments

This study was sponsored by the LeicestershireDermatology Research Foundation. The authors thankDr John Thompson PhD, Department of Ophthalmology,University of Leicester, for statistical advice.

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© 1997 British Association of Dermatologists, British Journal of Dermatology. 136, 498-501