Asthma prevalence in European, Maori, and Pacific children in New Zealand: ISAAC study

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<ul><li><p>Pediatric Pulmonology 37:433442 (2004)</p><p>Asthma Prevalence in European, Maori, and PacificChildren in New Zealand: ISAAC Study</p><p>Philip K. Pattemore, MD, FRACP,1* Lis Ellison-Loschmann,2 M. Innes Asher, MB ChB, FRACP,3</p><p>David M.J. Barry, MB ChB, FRACP,4 Tadd O. Clayton, MSc, DPH,3 Julian Crane, MB ChB, FRACP,5</p><p>Wendyl J. DSouza, MB ChB, FRACP,5 Philippa Ellwood, DPH,3 Rodney P.K. Ford, MD, FRACP,6</p><p>Richard J. Mackay, MB ChB, FRACP,7 Edwin A. Mitchell, DSc, MB BS, FRACP,3</p><p>Christoper Moyes, MD, MRCP,8 Neil Pearce, PhD,2 and Alistair W. Stewart, BSc, DipSc9</p><p>Summary. The International Study of Asthma and Allergies in Childhood (ISAAC) demonstrated</p><p>that the highest prevalence of asthma in the world is in English-speaking countries, including</p><p>New Zealand. In this paper, we compare asthma symptom prevalence in the three major ethnic</p><p>groups (Maori, Pacific, and European) in the six participating centers in New Zealand. Hospital</p><p>admission rates for asthma are higher among Maori and Pacific children compared to European</p><p>children. The working hypothesis was that there were important differences in prevalence of</p><p>asthma symptoms or diagnosis between ethnic groups which might explain these observed</p><p>differences in asthma morbidity. In each center in 19921993, we sampled approximately 3,000</p><p>children at each of the age brackets 67 years and 1314 years. There were 37,592 participants.</p><p>Maori children had higher rates of diagnosed asthma and reported asthma symptoms than Pacific</p><p>children in both age groups (diagnosed asthma in 67-year-olds: Maori, 31.7%; Pacific, 21.2%;</p><p>95%confidence interval on difference (CID), 7.2, 13.8;P&lt; 0.001; 1314-year-olds:Maori, 24.7%;</p><p>Pacific, 19.2%; CID 2.5, 8.5; P&lt; 0.001; recent wheeze in 67-year-olds: Maori, 27.6%; Pacific,</p><p>22.0%; CID, 2.6, 8.6; P</p></li><li><p>report may be one reason for the increased asthmamorbidity in these groups. Further studies are</p><p>needed to determine the reasons for these apparent differences in asthma severity. Pediatr</p><p>Pulmonol. 2004; 37:433442. 2004 Wiley-Liss, Inc.</p><p>Key words: asthma; wheezing; child; adolescence; prevalence; ethnic groups.</p><p>INTRODUCTION</p><p>The International Study of Asthma and Allergies inChildhood (ISAAC)1 demonstrated that the highest pre-valence of reported asthma symptoms in the world isin English-speaking countries, including the UK, NewZealand (NZ), Australia, the US, and Canada, as well assome parts of Latin America.2,3 We previously showed thatthe prevalence of reported asthma diagnosis and symptomsis similar across the six participating NZ centers.4</p><p>To date, there have been few studies of ethnic differ-ences in asthma prevalence in NZ. Previous studies foundhigher asthma morbidity and mortality among Maori andPacific children and adults than among European people.The Maori experience excess asthma morbidity and ahigher hospital admission rate compared to non-Maori.58</p><p>Pacific children and adults have higher hospital admissionrates than do European people in the same age groups.6,7</p><p>We do not know if these differences in asthma morbidityare due to differences in asthma prevalence or severity, orare due to other factors such as access to medical care andmanagement of asthma. It is therefore important to con-sider ethnic differences in asthma prevalence rates in theNZ ISAAC study,4 since this is the largest and mostcomprehensive study of prevalence of asthma symptomsin NZ children to date. A similar study performed inAuckland in 19859,10 enabled us to see if the prevalencerates and ethnic differences in asthma symptoms anddiagnosis had changed between 19851993.</p><p>The purpose of this paper is to compare the prevalenceand severity of asthma symptoms in Maori, European, andPacific 67-year-olds and 1314-year-olds in NZ, andto assess the consistency of these comparisons over time.We hypothesized that asthma prevalence would differbetween ethnic groups, and would explain at least in partthe differences in asthma morbidity. We also hypothesizedthat these differences and the prevalence rates would besimilar to those reported in the 1985 Auckland study.</p><p>METHODS</p><p>The methods of ISAAC Phase One in NZ have beenpublished,1,4 and will only be briefly summarized here.Six NZ centers participated in ISAAC Phase One, aninternational survey of asthma and allergies in children,which was conducted from 19921993. Three centerswere major urban areas, i.e., the Auckland metropolitanarea, Wellington City area, and Christchurch City area.The other three centers were rural areas centerd on aprovincial town: Bay of Plenty, Hawkes Bay, and Nelson.</p><p>We obtained approval for the study from regional ethicscommittees.</p><p>In each center, we selected primary and secondaryschools containing 67-year-old children or 1314-year-old young people, respectively, by sequential randomsampling among all schools in the relevant geographicalarea, until 3,000 children had been sampled in each agegroup, or all schools in the sampling frame had beensampled. All children of these age groups in the sampledschools were included in the sample. We sought permis-sion from the schools, and sent information sheets to allparents of sampled children. Parents of younger childrenconsented by completing the questionnaire; for the oldergroup, parents and the teenagers themselves were giventhe opportunity to decline the study.</p><p>The participating 67-year-old children took home aquestionnaire regarding asthma, eczema, and allergicrhinitis for their parents or guardians to complete. The1314-year-olds filled out their own questionnaires, andalso answered questions relating to a video of asthmasymptoms in young people. The written questionnairesand video were standardized for ISAAC worldwide.</p><p>We defined ethnicity by the parents designation of thechild or the young persons self-reported identity (Appen-dix). This corresponds to the method used in the NZCensus of 1991. In this paper, the designation Europeanmeans people identifying themselves as of Europeanancestry, equivalent to pakeha in Maori or whites inAmerican usage. The designation Pacific means peopleindicating Polynesian ancestry and affiliation, other thanMaori, including people from Samoa, Tonga, Niue,Tokelau, Fiji, and the Cook Islands. Respondents whoidentified more than one ethnic group were considered tobe Maori, if Maori was one of the groups identified,Pacific, if Pacific Island ethnicity but not Maori ethnicitywas included, and European only if neither Maori norPacific identification were mentioned. Those who answer-ed Other or did not answer were not included in thisanalysis.</p><p>We described differences between ethnic groups by95% confidence intervals on the pairwise differences inprevalence (CID), and by w2 probabilities based on 2 2contingency tables. Because the unit of sampling (schools)is different from the unit of analysis (individuals), tests ofsignificance were calculated using appropriate adjustmentof sample sizes. We used P&lt; 0.05 as our cutoff for statis-tical significance. In the rest of this paper, we refer toreported wheezing in the last 12 months as recentwheeze.</p><p>434 Pattemore et al.</p></li><li><p>Comparison of asthma symptoms among different NZcenters was reported previously.4 In the current paper, wecompared data from urban and provincial centers in thethree ethnic groups to see whether there were similarpatterns of ethnic differences in these two types of center.</p><p>We compared our results for 67-year-olds in theAuckland center with a study of 810-year-old children inAuckland in 1985.9,10 That age group lies between the twoage groups in the present study. Like the children in theAuckland study, the 67-year-olds in the present studywere prepubertal children, and were studied by parent-completed questionnaire, whereas the 1314-year-oldswere studied by self-completed questionnaire. Althoughwe were comparing slightly different ages, there were nosignificant differences across age between 810 years oldin the Auckland study. The geographical sampling area in1985 was the same as the Auckland sample in the presentstudy, but in 1985 only every second European childsequentially sampled in class lists was studied. This doesnot affect the comparisons between ethnic groups, exceptto decrease the size of the European sample in 1985, andhence the power of comparisons. Ethnicity was askedfor and defined in a similar way (see Appendix). TheAppendix shows the particular questions we compared inthe two studies. We described the change in rates betweenthe two studies by the ratio of the 1993 prevalence figuresto the relevant 1985 prevalence figures. These ratios weretreated as relative risks (with time as the exposure) toestimate 95% confidence intervals (CI). This enabled us todetermine by what proportion the prevalence of certainresponses had changed. The effect of cluster sampling(design effect) was not taken into account in this com-parison, as we did not have access to the raw data relatingto individual clusters for the 1985 study.</p><p>RESULTS</p><p>The participation rate by ethnic group and age group isgiven in Table 1, along with 1991 NZ Census data. Theoverall response rates were 91% in 67-year-olds and93% in 1314-year-olds. Proportions of different ethnicgroups in the participants very closely matched propor-tions in the relevant age bracket in the 1991 NZ Census.Ninety-eight percent of schools for the 67-year agegroup participated (range, 96100% among centers), and87% for the 1314-year age group (range, 73100%). Theprevailing reason for schools declining was curricularpressure.</p><p>The number of schools sampled per center rangedfrom 4583 for 67-year-olds, and from 1235 for 1314-year-olds. The mean number of sampled students persampled school in each center ranged from 4268 (overallmean, 49) for 67-year-olds, and from 83227 (overallmean, 180) for 1314-year-olds. The mean design effectfor recent wheeze from school-based sampling was 1.3 for T</p><p>AB</p><p>LE</p><p>1</p><p>Part</p><p>icip</p><p>ati</p><p>on</p><p>by</p><p>Eth</p><p>nic</p><p>ity</p><p>an</p><p>dA</p><p>ge</p><p>Gro</p><p>up</p><p>1</p><p>Eth</p><p>nic</p><p>ity</p><p>6</p><p>7y</p><p>ears</p><p>NZ</p><p>po</p><p>pu</p><p>lati</p><p>on</p><p>19</p><p>91</p><p>Cen</p><p>sus</p><p>eth</p><p>nic</p><p>dis</p><p>trib</p><p>uti</p><p>on</p><p>of</p><p>5</p><p>9-y</p><p>ear-</p><p>old</p><p>s(%</p><p>)</p><p>13</p><p>1</p><p>4y</p><p>ears</p><p>NZ</p><p>po</p><p>pu</p><p>lati</p><p>on</p><p>19</p><p>91</p><p>Cen</p><p>sus</p><p>eth</p><p>nic</p><p>dis</p><p>trib</p><p>uti</p><p>on</p><p>of</p><p>10</p><p>1</p><p>4-y</p><p>ear-</p><p>old</p><p>s(%</p><p>)</p><p>Res</p><p>po</p><p>nse</p><p>rate</p><p>(%)</p><p>Par</p><p>tici</p><p>pan</p><p>ts</p><p>Pro</p><p>po</p><p>rtio</p><p>no</p><p>fto</p><p>tal</p><p>sam</p><p>ple</p><p>(%)</p><p>Res</p><p>po</p><p>nse</p><p>rate</p><p>(%)</p><p>Par</p><p>tici</p><p>pan</p><p>ts</p><p>Pro</p><p>po</p><p>rtio</p><p>no</p><p>f</p><p>tota</p><p>lsa</p><p>mp</p><p>le(%</p><p>)</p><p>Eu</p><p>rop</p><p>ean</p><p>95</p><p>.11</p><p>2,1</p><p>90</p><p>65</p><p>.76</p><p>8.6</p><p>95</p><p>.71</p><p>2,3</p><p>87</p><p>65</p><p>.17</p><p>0.0</p><p>Mao</p><p>ri8</p><p>4.8</p><p>3,7</p><p>47</p><p>20</p><p>.22</p><p>0.3</p><p>90</p><p>.03</p><p>,93</p><p>82</p><p>0.7</p><p>19</p><p>.6</p><p>Pac</p><p>ific</p><p>83</p><p>.81</p><p>,41</p><p>27</p><p>.66</p><p>.79</p><p>4.4</p><p>1,4</p><p>07</p><p>7.4</p><p>6.5</p><p>Oth</p><p>er8</p><p>0.1</p><p>1,2</p><p>20</p><p>6.6</p><p>4.4</p><p>82</p><p>.31</p><p>,29</p><p>16</p><p>.83</p><p>.9</p><p>To</p><p>tal</p><p>90</p><p>.91</p><p>8,5</p><p>69</p><p>10</p><p>0.0</p><p>93</p><p>.41</p><p>9,0</p><p>23</p><p>10</p><p>0.0</p><p>1R</p><p>esp</p><p>on</p><p>sera</p><p>tes</p><p>by</p><p>eth</p><p>nic</p><p>gro</p><p>up</p><p>are</p><p>calc</p><p>ula</p><p>ted</p><p>bas</p><p>edo</p><p>nsc</p><p>ho</p><p>ols</p><p>as</p><p>sess</p><p>men</p><p>to</p><p>fet</p><p>hn</p><p>icit</p><p>yo</p><p>fin</p><p>div</p><p>idu</p><p>aln</p><p>on</p><p>par</p><p>tici</p><p>pan</p><p>ts.</p><p>Asthma Prevalence and Ethnicity in NZ 435</p></li><li><p>TA</p><p>BL</p><p>E2</p><p>6</p><p>7-Y</p><p>ear-</p><p>Old</p><p>s:</p><p>Wh</p><p>eeze</p><p>an</p><p>dA</p><p>sth</p><p>ma</p><p>Pre</p><p>val</p><p>ence</p><p>(%)</p><p>Dif</p><p>fere</p><p>nce</p><p>inp</p><p>reval</p><p>ence</p><p>(95</p><p>%co</p><p>nfi</p><p>den</p><p>cein</p><p>terv</p><p>al</p><p>on</p><p>dif</p><p>fere</p><p>nce</p><p>),p</p><p>rob</p><p>abil</p><p>ity</p><p>of</p><p>the</p><p>dif</p><p>fere</p><p>nce</p><p>occ</p><p>urr</p><p>ing</p><p>by</p><p>chan</p><p>ce1</p><p>Eu</p><p>rop</p><p>ean</p><p>Mao</p><p>riP</p><p>acifi</p><p>cE</p><p>uro</p><p>pea</p><p>n-M</p><p>aori</p><p>Eu</p><p>rop</p><p>ean</p><p>-Pac</p><p>ific</p><p>Mao</p><p>ri-P</p><p>acifi</p><p>c</p><p>Ast</p><p>hm</p><p>aev</p><p>er2</p><p>5.9</p><p>31</p><p>.72</p><p>1.2</p><p>5.8(</p><p>7.9,3</p><p>.7)P</p></li></ul>

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