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National Collaborating Centre for Women's and Children's Health (UK). Atopic Eczema in Children: Management of Atopic Eczema in Children from Birth up to the Age of 12 Years. London: RCOG Press; 2007 Dec. (NICE Clinical Guidelines, No. 57.)

5Epidemiology

Studies considered in this chapter

Studies focusing on the epidemiology of atopic eczema in children (prevalence, age of onset and resolution, frequency, location and extent of flares, associations with asthma, hay fever and food allergies, and variations in different ethnic groups) as their prime objective were considered for this section. Preference was given to reviews of observational studies and to data from the UK. Where data from the UK were not available, studies conducted in other countries were included. It is recognised that some epidemiological data may be reported in other publications which are not considered here because their primary objectives did not include investigation of the epidemiology of atopic eczema in children.

Overview of available evidence

Two reviews that were published as chapters in textbooks were identified. Literature searches for both reviews were undertaken systematically, but the eligibility criteria were not stated and therefore the reviews have been given a low evidence level.114,115 [EL = 3]

Point prevalence

Several studies have considered the epidemiology of atopic eczema in children. However, differences in study populations evaluated, in the definition of atopic eczema and in survey methods result in a wide range of prevalence estimates.

A review (end search date year 2000) found 30 studies that measured the prevalence of atopic eczema in the 1990s, 26 of which included children aged up to 12 years (solely or predominantly).114 In the five studies conducted in the UK (1992 to 1996), point prevalence rates ranged from 5.9% (using the UK Working Party Diagnostic Criteria in 3- to 11-year-olds, n = 1523) to 14.2% (dermatologist’s examination in 4-year-olds, n = 260). [EL = 3]

Two studies provided some data for trends in point prevalence rates over time for the UK, one of which was recently updated.116,117 One reported that in children aged 12 years in South Wales the prevalence of ever having had atopic eczema increased from 15.9% in 1988 to 23.1% in 2003 (n = 1148).117 The second study, in children aged 8–13 years in Aberdeen, found that the point prevalence of eczema increased from 5.3% in 1964 to 12% in 1989 (n = 2510 and 3403, respectively).116

Studies in Scandinavia, Germany and Japan that considered point prevalence or cumulative incidence of atopic eczema in children of the same age (6, 7, or 7–13 years) born in different years showed that the prevalence increased from the 1980s to the 1990s. The increases were from 8.6% to 13% in 6-year-olds,118 18.9% to 19.6% in 7-year-olds,119 13.2% to 19.7% in 7- to 13-year-olds,120 15% to 22.9% in 7- to 12-year-olds,121 8.6% to 11.8% in 9-year-olds,118 and 9.6% to 10.2% in 12-year-olds.118 [EL = 3]

Period prevalence

Two studies reported period prevalence of atopic eczema in children in the UK. A 1 year period prevalence of 11.5% was reported for schoolchildren aged 3–11 years in Birmingham (n = 1077).122 In a study in children aged 1–5 years, the 1 year period prevalence was 16.5% (n = 1523).123 The International Study of Asthma and Allergies in Childhood (ISAAC) found that the 12 month period prevalence in 6- to 7-year-olds in the UK was 13% (n = 1864). The worldwide figures ranged from under 2% in Iran to over 16% in Japan and Sweden (n = 256 410 in 90 centres).124,125

In a cohort of children in the UK followed from birth to 10 years of age, the period prevalence of atopic eczema was 9.6% at age 1 year, increasing to 10.3% at 2 years, 11.9% at 4 years and 14.3% at 10 years. Lifetime prevalence of atopic eczema was 41% at 10 years of age. Of the 41% of children who had ever had atopic eczema, 56.3% still had the condition at age 10 years (n = 1456).126 Another UK cohort study found that lifetime prevalence was 25.3% at age 8 years, with annual point prevalence ranging from 8.3 to 10.6%.127 [EL = 3]

Geographical variation in prevalence

Data from the 1958 British Birth Cohort study, showed regional differences in prevalence (n = 8278). The lifetime prevalence of parent-reported eczema (it was not stated whether the eczema was atopic) in 7-year-old children ranged from 5.3% in the North-West region of England to 10.8% in the Eastern region (prevalence rates in Scotland and Wales were within this range). The point prevalence of eczema examined by school medical officers was lower than for parent-reported eczema, ranging from 1.7% to 4.7%.128 [EL = 3] It is not known whether these regional prevalence figures reflect current patterns. The ISAAC study did not report prevalence rates by region. Potential reasons for geographical differences in the prevalence of atopic eczema could include differences in social class, pollution and water hardness. Factors that might trigger exacerbations of established atopic eczema are considered in Section 6.1.

Prevalence in different ethnic groups

Two observational studies from the UK considered the epidemiology of eczema in different ethnic groups. The first reported the prevalence of atopic eczema in Asian and non-Asian children in Leicester (n = 413).129 The study found no difference in the point prevalence or lifetime prevalence of atopic eczema in Asian and non-Asian children:

  • point prevalence 9% versus 11%, 95% CI for the difference −3.8% to 8.9%
  • lifetime prevalence 16% versus 15%, 95% CI for the difference −7% to 7%.

Similarly there was no significant difference in the severity of atopic eczema between Asian and non-Asian children (mean SASSAD score 6.3 (SD 3.7) versus 7.3 (SD 3.5)).129 [EL = 3]

In schoolchildren aged 3–11 years in London, the point prevalence of atopic eczema diagnosed by a paediatric dermatologist was 11.7% (n = 693). The prevalence appeared to be higher in black Caribbean children than in white children, although the statistical significance of this was dependent on the criteria used to diagnose the eczema (statistically significant for the dermatologist’s diagnosis, parental report and the criterion ‘history of flexural itchy rash’, but not statistically significant when the sign visible flexural dermatitis was considered).130 [EL = 3]

Incidence and age of onset

A UK study considered the incidence of atopic eczema in children aged up to 2.5 years born in 1991 and 1992. The incidence was highest during the first 6 months of life (21%), falling to 11.2% by the age of 6–18 months, and to 3.8% by the age of 30 months (2.5 years). The corresponding period prevalence rates were highest at age 6–18 months (25.6%) compared with 21% at 0–6 months, 23.2% at 18–23 months, and 19.9% at 30–42 months (2.5–3.5 years; n = 8530).131 [EL = 3]

The age of onset of atopic eczema was considered in one of the reviews,115 which identified eight studies published between 1948 and 1989. The countries where the studies were conducted were not made clear. The data were derived from individuals who were hospitalised or attending specialist clinics. The age of onset of atopic eczema was less than 1 year in between 42% (n = 100) and 88% (n = 121) of individuals (the age at follow-up was up to 50 years).115 [EL = 3] In a UK community cohort study (the 1958 British Birth Cohort study) which was included in the review, 66% of those with examined or reported atopic eczema at the age of 16 years had developed the condition by the age of 7 years (n = 1053).115,132 [EL = 3]

A further five observational studies conducted in the UK were identified.95,122,126,127,133 [EL = 3] Three of the studies considered the age at presentation with eczema and made the following observations:

  • atopic eczema had presented during the first year of life in 68% of children aged 5–10 years with the condition (n = 137; recruited from general practice); children who developed atopic eczema during the first year of life were more likely to have severe eczema (adjusted OR 2.1, 95% CI 1.2 to 3.2)133
  • 71.0% of children aged 10 years who had atopic eczema symptoms in the previous year had first developed atopic eczema before the age of 4 years (n = 1456)126
  • the median age at onset was 6 months in children aged 3–11 years (n = 1077; 204 with eczema).122 [EL = 3]

Two of the studies considered the age at which the diagnosis was made:

  • in children with atopic eczema aged 15 years or under, 93% of diagnoses were made in the first 2 years of life (n = 429)95
  • in a birth cohort, 56.7% of those aged 8 years who had ever been diagnosed with atopic eczema were diagnosed by the age of 2 years (n = 592).127 [EL = 3]

Disease severity

Epidemiological data from studies involving several countries collated in one of the reviews114 showed that 65–90% of community cases of atopic eczema were of mild severity, with only 1–2% classified as severe. It was noted that there was a lack of data relating severity of atopic eczema to age.114 [EL = 3]

In children aged 1–5 years in the UK, 84% were considered to be mild, 14% moderate, and 2% severe (n = 1760, dermatologist’s rating).123 In older children in the UK (aged 5–10 years), similar figures were reported using the SCORAD instrument: atopic eczema was mild in 80% of children, moderate in 18% and severe in 2% (n = 137).133 The ISAAC study reported that the 12 month period prevalence of severe eczema in the UK was 2.0%.124

Prognosis

One of the reviews115 identified 25 studies that investigated the long-term prognosis of atopic eczema, 22 of which included children aged under 12 years at study inception (studies were reported between 1930 and 1997). Only data from studies that included children at inception were considered here. The countries in which the studies were conducted were not made clear. Most of the studies included individuals who had been treated as hospital inpatients or outpatients. Data were gathered by questionnaire and/or physical examination and losses to follow-up were common, ranging from about 3% to 73% (median 31%). The studies identified atopic eczema as a chronic condition with a 10 year clearance rate of 50–70%, although a wide range of clearance rates over varying follow-up periods were reported (11–92%). Several studies found that individuals who were apparently clear of atopic eczema subsequently experienced a relapse at a later point, which may reflect differences in use of terms such as clearance and remission.115 [EL = 3] The general findings of this review should be treated with caution because studies with prognostic data from decades ago may not be directly transferable to the present day owing to changes in factors affecting the condition. [EL = 4]

The British Birth Cohort study reported that, of the children with atopic eczema at age 7 years, 65% were clear of reported or examined eczema at the aged of 11 years, and 74% at the age of 16 years. However, these apparent clearance rates fell to 53% and 65%, respectively, when adjusting for subsequent recurrences in teenage years or adulthood (n = 571).132

One further study considered prognosis. In children in Germany who developed atopic eczema before the age of 2 years, 43.2% were in ‘complete remission’ by the age of 3 years, 38.3% had an intermittent pattern of disease up to the age of 7 years, and 18.7% had symptoms every year up to the age of 7 years (n = 192). There was no difference in prognosis between children who first developed atopic eczema in the first and second years of life. Children who reported frequent scratching before the age of 2 years were more likely to have a poor prognosis and still have atopic eczema at the age of 7 years (cumulative OR 5.86, 95% CI 3.04 to 11.29).134 [EL = 3]

Frequency, location and extent of flares

Atopic eczema typically has an intermittent pattern of flares which may occur rapidly and usually last from a few days to several weeks. Flares tend to recur in the same sites within individuals.115 The frequency of flares is described in Section 7.7.

No UK data were found regarding the anatomical areas affected with atopic eczema in children. A study of children aged up to 10 years in Japan found a change in distribution of atopic eczema in children between the age of 1 and 2 years from the head, scalp and around the ears to the neck and flexures. The trunk was the most commonly affected area at all ages (n = 1012).115,135

A study in Nigeria found that atopic eczema was more often located in extensor areas in children aged 0–3 years, whereas in children aged 3–18 years atopic eczema was more often seen in flexural areas (n = 1019, aged 4 weeks to 57 years).136 [EL = 3] A study in Kenya found that initial presentation of atopic eczema in children aged 0–12 years at the time of examination involved facial or extensor sites in 86% of children. Although this pattern continued into later childhood, flexural involvement was more common in children older than 1 year compared with those aged less than 1 year (73% versus 37.5%).137 [EL = 3]

Associations with asthma, hay fever and food allergies

One of the reviews found seven studies that investigated the development of asthma and/or hay fever (allergic rhinitis) in children with atopic eczema.115 Concurrent or subsequent asthma was present in 10–53% (median 28%) and hay fever in 12–78% (median 59%). One study reported that more children with atopic eczema who attended as inpatients for their condition subsequently developed asthma (39%) compared with 22% of those treated only as outpatients (age 24–44 years at the time of follow-up). A confounding factor was that atopic eczema was more likely to be severe in children attending a hospital clinic, which is in itself a risk factor for the subsequent development of asthma. The review also reported that none of the studies set out to examine the association between asthma and atopic eczema and that few studies used clear definitions for asthma.115 [EL = 3]

Three further surveys investigated the prevalence of asthma in children with atopic eczema in the UK. [EL = 3] They reported the following:

  • 43% of children aged 5–10 years from general practice with atopic eczema had asthma, 45% had hay fever and 64% had asthma and/or hay fever (n = 137); atopic eczema was more likely to be severe in children with asthma (adjusted OR 2.0, 95% CI 1.1 to 3.6) or hay fever (adjusted OR 2.42, 95% CI 1.39 to 4.2)133
  • 38% of children aged 3–11 years also had asthma at some time point (n = 1077)122
  • the asthma prevalence was 17% in children with atopic eczema who were aged 0–2 years, increasing to 39% in those aged 3–7 years, and 42% in those aged 8–15 years (n = 429).95

One observational study in Sweden reported that 3.1% of children aged 1–2 years with atopic eczema also had hay fever (allergic rhinoconjunctivitis). The condition was more common in children with atopic eczema than in those without (12.3% versus 5.2%, ‘ratio adjusted for heredity’ 2.25, 95% CI 1.77 to 2.85).138 [EL = 3]

The German multicentre atopy study (MAS)139–141 reported that the lifetime prevalence of asthma was 10% at 1 year of age and 15% at 2 years of age (n = 1314).139 The risk of having allergic airway disease (asthma and/or hay fever) at 5 years of age was higher (but not significantly so) in children who developed atopic eczema in the first 3 months of life.141

Food allergy

Several tests can be used to investigate whether a child is sensitised to foods, including skin prick tests and specific immunoglobulin E (IgE) measurements. However, the double-blind placebo-controlled food challenge (DBPCFC) is the gold standard for diagnosing food allergy in children. (The details of these and other tests and the proportions of positive reactions to food challenges in children in whom food allergy is being investigated are described in Chapter 6). No UK data were identified regarding food allergy or sensitisation in children with atopic eczema.

One study evaluated the prevalence of IgE-mediated reaction to foods in children and adults (aged 0.4–19.4 years, median age 2.8 years) with moderate to severe atopic eczema (mean SCORAD score 43) who were referred to a dermatologist. Overall, 65% had raised IgE levels (more than 0.7 ku/l) to at least one of six foods (milk, egg, peanut, wheat, soya and fish).143 [EL = 3]

In infants aged 1 year (the Melbourne birth cohort) who were identified as being at risk of atopic disease, the prevalence of atopic eczema was 28.9%. The prevalence of IgE-mediated food allergy (wheal diameter of skin prick test at least twice that of the positive control (histamine)) was significantly higher in those with atopic eczema than those without (35% versus 12%, relative risk (RR) of atopic eczema because of IgE-mediated food allergy 3.1, 95% CI 2.1 to 4.4). The prevalence of IgE-mediated food allergy also increased with increasing severity.144 [EL = 3]

Changes in sensitisation with age

Several studies have shown how sensitisation to various allergens changes with age. A short report comparing children with atopic eczema who were aged 2–4 years with those aged 10–12 years (n = 22) noted that sensitisation to food allergens (egg white, cow’s milk, cod, wheat, peanut and soya) decreased with age, whereas sensitisation to common inhalant allergens (including house dust mite, grass, and tree pollen) increased with age.145 [EL = 3] Another case series found a significant association between sensitisation to food allergens and atopic eczema in children aged under 2 years, which did not remain significant above this age. Conversely, the association between inhalant allergens (house dust mite and cockroach) increased with age, becoming statistically significant after the age of 5 years (n = 262).146 [EL = 3]

The German MAS study139–141 reported that the lifetime prevalence of food intolerance was 3% at 1 year of age and 4.5% at 2 years of age. Sensitisation (to one of nine allergens; IgE level of 0.35 ku/l or more) was 16% at 1 year and 24% at 2 years (n = 1314).139 At 5 years, the proportion sensitised to inhalant allergens was higher than that sensitised to food allergens (28% versus 22.3%).141 The odds of having sensitisation to inhalant allergens was significantly higher in children who had developed atopic eczema in the first 3 months of life.141 In a subgroup of this population in whom complete specific IgE data were obtained, IgE levels specific to inhalant allergens were significantly higher than IgE levels specific to food allergens in children of the same age from the age of 3 years, P < 0.006 (n = 216). The proportion of children with atopic eczema in this subgroup was not stated.140

A Danish cohort study (n = 553) looking at sensitisation patterns in infants identified 61 children who had ever been diagnosed with atopic eczema between 3 and 18 months of age.147 [EL = 2−] Children sensitised to at least one allergen were more likely to have atopic eczema than those who were sensitised to no allergens. Odds ratios depended on the measurement technique used (skin prick test, histamine release or IgE). Persistent sensitisation was also associated with atopic eczema when measured by skin prick test or specific IgE, but not by histamine release. Confidence intervals were wide.

Sensitisation and severity of atopic eczema

The level of sensitisation to cow’s milk and egg was measured in the placebo arm of the Early Treatment of the Atopic Child (ETAC) study (an RCT comparing the antihistamine cetirizine with placebo) over the 18 month follow-up period. Sensitisation was defined as a specific IgE level of 0.35 ku/l or more (n = 382). The correlation between specific IgE levels and the severity of atopic eczema (SCORAD) was statistically significant for egg at all time points (months 0, 3, 12 and 18) and for cow’s milk at months 0, 12 and 18).148 [EL = 3] In a case–control study, 27% of children with atopic eczema (cases) had a positive skin prick test result for common food allergens (cow’s milk, egg, cod, soya, peanut and wheat), and 15% a positive test result to IgE (no further details reported). Although no data were reported, it was noted that there was no significant difference in objective SCORAD scores in sensitised and non-sensitised cases with ongoing atopic eczema (n = 320).149 [EL = 2−]

A smaller case series reported that 64% of children (mean age 3.5 years) had positive skin prick test results for food and/or inhalant allergens (n = 50). A significant association between sensitisation and severity (SASSAD score) was also reported.150 [EL = 3]

Evidence statement for epidemiology

There has been little consistency among epidemiological studies of atopic eczema in children with regard to the populations studied or the methods used, leading to wide variations in the results reported in individual studies. It is not possible to give a definitive prevalence of atopic eczema. Prevalence may vary according to geographical location within the UK, but it is not clear whether it is location per se or other factors that influence the differences in prevalence figures. There are too few data on prevalence in different ethnic groups to allow conclusions to be drawn. Studies conducted in the UK over the past 30 years have shown a four-fold increase in the point prevalence of atopic eczema in children. Studies conducted in other countries in the 1980s and 1990s have also shown an increase in prevalence. [EL = 3]

In the majority of children, atopic eczema develops before the age of 4 years. In infants, atopic eczema commonly affects cheeks and extensor surfaces rather than flexural areas. [EL = 3]

Observational studies have shown that the majority of cases of atopic eczema are mild in severity. There is a lack of data relating severity of atopic eczema to age. There is some evidence that eczema is more likely to be severe in children who also have asthma, and in those with early onset of atopic eczema. [EL = 3] It is not clear whether prognosis is better in children with mild disease. [EL = 4]

The available data suggest that atopic eczema clears in most children by the teenage years and early adulthood, although relapses may occur. [EL = 3]

Atopic eczema is more likely to be severe in children who also have asthma or hay fever (one study). Varying prevalence rates for concurrent asthma and hay fever have been reported. The proportion of children sensitised to foods and inhalant allergens varies across studies. However, studies consistently show that sensitisation to foods decreases with age whereas sensitisation to inhalant allergens increases from the age of about 3–5 years. [EL = 3]

Cost-effectiveness

No cost-effectiveness issues could be addressed in relation to the epidemiology of atopic eczema because the use of healthcare resources was not the focus of the clinical question.

From evidence to recommendations

The GDG believes that it is important to provide information for children with atopic eczema and their parents/carers on the prognosis of the disease and possible associations between atopic eczema and other atopic diseases.

Recommendations for epidemiology

Healthcare professionals should inform children with atopic eczema and their parents or carers that the condition often improves with time, but that not all children will grow out of atopic eczema and it may get worse in teenage or adult life.

Healthcare professionals should inform children with atopic eczema and their parents or carers that children with atopic eczema can often develop asthma and/or allergic rhinitis and that sometimes food allergy is associated with atopic eczema, particularly in very young children.

There were no research recommendations on epidemiology.

Copyright © 2007, National Collaborating Centre for Women’s and Children’s Health.

No part of this publication may be reproduced, stored or transmitted in any form or by any means, without the prior written permission of the publisher or, in the case of reprographic reproduction, in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK [www.cla.co.uk]. Enquiries concerning reproduction outside the terms stated here should be sent to the publisher at the UK address printed on this page.

The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore for general use.

Cover of Atopic Eczema in Children
Atopic Eczema in Children: Management of Atopic Eczema in Children from Birth up to the Age of 12 Years.
NICE Clinical Guidelines, No. 57.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2007 Dec.

NICE (National Institute for Health and Care Excellence)

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