International Journal of Pediatrics

Volume 2013 (2013), Article ID 963132, 7 pages

http://dx.doi.org/10.1155/2013/963132

Clinical Study

Ear Infection and Its Associated Risk Factors, Comorbidity, and Health Service Use in Australian Children

Vasoontara Yiengprugsawan¹ and Anthony Hogan²

¹The Australian National University, National Centre for Epidemiology and Population Health Acton, Canberra, ACT 2601, Australia

²ANZSOG Institute for Governance, University of Canberra, Acton, Canberra, ACT 2617, Australia

Received 28 February 2013; Revised 30 April 2013; Accepted 23 May 2013

Academic Editor: Joel R. Rosh

Copyright © 2013 Vasoontara Yiengprugsawan and Anthony Hogan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

This study investigates and identifies risk factors, comorbidity, and health service use related to ear infection in Australian children. Two cross-sectional analyses of the Longitudinal Study of Australian Children (LSAC) involved 4,983 children aged 4 to 5 years in 2004 and aged 10 to 11 years in 2010. Odds ratios (ORs) were analysed using bivariate logistic regression. The prevalence of parent-reported ear infection was 7.9% (394) among children aged 4 to 5 years and 3.3% (139) at 10 to 11 years. Our study found that risk factors associated with ear infection were indigenous status, not being breastfed, mother or father smoking at least once a day, and father’s school completion at year 9 or lower. By age 10 to 11 years significantly reported comorbidities were tonsillitis (OR 4.67; ), headache (OR 2.13; ), and asthma (OR 1.67; ) and ear infection was found to be associated with the use of pediatrician (OR 1.83; ), other specialist (OR 2.12; ), and early intervention services (OR 3.08; ). This empirical evidence can be used to inform the development of intervention and management programs for ear infection.

1. Introduction

Middle ear infection is a common, yet treatable disease and is a major cause of morbidity in children. If left untreated, long-term consequences of persistent severe ear infection can arise including speech development disorders [1], academic and educational development [2, 3], and lower overall quality of life [4, 5]. Subsequent hearing loss is one of the long-term implications of ear infection found to be associated with behavioural disorders and subsequent risks for longer-term mental health problems in children [6, 7]. Increased knowledge of the risk factors associated with ear infection is important in identifying children at risk for recurrent and persistent episodes [8].

Reviews of several European countries, the United States, Canada, and Australia have shown risk factors for ear infection to be childcare arrangement, breastfeeding, birth weight, socioeconomic status, and air pollution [9–11]. In a study of a birth cohort in Canada, the strongest risk factors for ear infection were being male, of Aboriginal status, and the child’s mother aged less than 20 years [12]. A recent study in Australia has shown poor living conditions, exposure to cigarette smoke, and lack of access to medical care are all major risk factors for ear infection [13]. Ear infections are often mild and frequently resolve themselves within a short period of time. However, the frequency of infection and its associated comorbidity (e.g., fevers and respiratory tract infections) are significant concerns [14]. Substantial co-morbidity has been demonstrated between upper and lower airway infections which include otitis media, tonsillopharyngitis, and lower respiratory infections [15].

The prevalence of ear infection, whereby Australian indigenous children had at least an episode in the first year of life, is among the highest in the world and has resulted in a wide range of complications [16, 17]. According to data from Aboriginal Medical Service, rural and remote practitioners manage a greater caring burden than their urban counterparts; hence, affected children have less access to specialist ear health services and longer waiting times [18].

Based on a nationally representative sample of Australian children in the same cohort, this study compares the prevalence of ear infection and associated sociodemographic risk factors, health covariates and comorbidity, and health service use at two time points: first at the age of 4 to 5 years and again at the age of 10 to 11 years. This study will provide current insights into evidence-base ear infection in Australian children which in turn may be used in the management, prevention, and intervention of ear infection [19, 20].

2. Data and Methods

2.1. Longitudinal Study of Australian Children Survey (LSAC)

The LSAC dataset was used to identify the key factors influencing children in the early years of development, using a longitudinal design to examine determinants and life course psychosocial health and well-being outcomes [21, 22]. The study used a two-stage clustered sampling design, stratified by state and by metropolitan/urban status. The Medicare database, which includes 98% of all Australian children, was used for recruitment. Details on development of questions, study design, and nonresponse are reported in other publications [22, 23].

Recruitment to the study of over 10,000 children and their families took place from March until November 2004. From 2004, the families have been interviewed every two years. Two child cohorts were recruited in 2004: those born between March 1999 and February 2000 (aged 4-5 year) and those born between March 2003 and February 2004 (aged 0-1 year). Compared to the Australian Bureau of Statistics population estimates, LSAC is broadly representative of the population, with about 10% more educated parents represented and about 5% less non-English speaking families [24, 25].

2.2. Study Population and Statistical Analyses

The analysis includes 4,983 children aged 4 to 5 years at 2004 baseline and 10 to 11 years in 2010. Sociodemographic characteristics of the sample reported in this study included sex, indigenous status of the study child, and the Australian Bureau of Statistics Socioeconomic Indexes for Areas (SEIFA) [26]. Population sample weights were provided with the dataset to achieve national representation.

Exposures and outcomes of interest in this study are as follows.

 Ear infection as reported by parent (in most cases this is the child’s biological mother) as follows: “Does a study child have ear infection (yes, no)?” It is likely that the reported ear infections include acute otitis media, chronic suppurative otitis media, otitis media with effusion, and uncommon ear diseases. However, nature or severity of ear infections was not reported.  Sociodemographic characteristics available in this study include sex and indigenous status of the study child, history of being breastfed, school attendance, parental smoking status, and parental school completion. As well, the study reported on respondents’ Socioeconomic Indexes for Areas (SEIFA) which ranks the respondent’s residential area by the level of social and economic well-being in each region.  Other health conditions were asked: “Does a study child have any of these ongoing problems… (yes, no)?” Health conditions include asthma, headache, tonsillitis, vision problems, other illnesses, and other infections.  Health service use was asked “In the last 12 months, have you used any of these services for the study child?… (yes, no)” Health service use includes general practitioners, hospital outpatients, pediatrician, and speech therapy. Other service categories include early intervention services and other specialists.

For variable selection on ear infection and risk factors, health comorbidity, and health service use, we systematically went through the questions available in the LSAC data and included variables of interest for investigation based on relevant national and international literature [9–15].

Association between ear infection and risk factors, health co-morbidity, and health service use was reported with the percent prevalence as well as odds ratios and values based on the results from bivariate logistic regression. Data were analysed using Stata 12 [27].

3. Results

Prevalence of ear infection was 7.9% (394) at the age of 4 to 5 years and 3.3% (139) at the age of 10 to 11 years. Table 1 presents sample distribution, ear infection prevalence, and cross-sectional association of ear infection and potential risk factors. The gender ratio within the sample was almost equally split (51% male; 49% female) among the children. Approximately 4% of study children had indigenous status. Approximately 80% reported being breastfed at 1 month, 71% at 3 months, and 57.2% at 6 months. As well, approximately 58.2% of children attended preschool, 24.5% participated in daycare, and 17.4% in kindergarten. Approximately 20% of mothers reported smoking more than once a day; and a similar proportion for fathers. Having less than year 9 school completion or less was reported by 6.9% of mothers and 5.9% of fathers.

Table 1: Prevalence and cross-sectional association of ear infection and potential risk factors.

At baseline age 4 to 5 years
% ()
Ear infection prevalence % ()
Bivariate odds ratio and value

Study child—sex

    Male
50.9 (2537)
8.5 (215)
OR = 1.00

    Female
49.1 (2446)
7.3 (179)
OR = 0.85; = 0.131

Study child—indigenous status

    Nonindigenous
96.3 (4794)
7.7 (368)
OR = 1.00

    Indigenous
3.8 (187)
13.9 (26)
OR  =  1.94; P   =  0.002

Reported breastfed (months)

    1 month—yes
80.2 (3976)
7.6 (301)
OR = 1.00

    1 month—no
19.8 (981)
9.2 (90)
OR = 1.23; = 0.096

    3 months—yes
71.0 (3518)
7.4 (260)
OR = 1.00

    3 months—no
29.0 (1439)
9.1 (131)
OR  =  1.25; P   =  0.043

    6 months—yes
57.2 (2833)
7.3 (207)
OR = 1.00

    6 months—no
42.9 (2124)
8.7 (184)
OR = 1.20; = 0.080

Mother—smoking status

    Not smoking
76.9 (3178)
7.4 (235)
OR = 1.00

    Less than once/day
3.6 (148)
6.1 (9)
OR = 0.81; = 0.550

    More than once/day
19.5 (805)
10.1 (81)
OR  =  1.40; P   =  0.013

Father—smoking status

    Not smoking
75.4 (2451)
7.0 (172)
OR = 1.00

    Less than once/day
3.2 (104)
7.7 (8)
OR = 1.10; = 0.792

    More than once/day
21.4 (696)
9.6 (67)
OR  =  1.41; P   =  0.022

Mother—school completion

    Year 12+
58.1 (2895)
7.6 (219)
OR = 1.00

    Year 10-11
34.9 (1739)
8.2 (143)
OR = 1.10; = 0.376

    Year ≤9
6.9 (344)
9.3 (32)
OR = 1.18; = 0.399

Father—school completion

    Year 12+
45.1 (2246)
6.5 (146)
OR = 1.00

    Year 10-11
33.8 (1682)
9.1 (153)
OR  =  1.43; P   =  0.003

    Year ≤9
5.9 (295)
9.5 (28)
OR  =  1.45; P   =  0.008

SEIFA economic resources

    Equal or above median
54.2 (2699)
7.4 (200)
OR = 1.00

    Below median
45.8 (2284)
8.5 (194)
OR = 1.16; = 0.158

Bivariate association was reported between ear infection and potential risk factors most relevant for children aged 4 to 5 years (Table 1, data not shown for children aged 10 to 11 years). Statistically significant odds ratios and values for risk factors were indigenous status (OR 1.94; ), not being breastfed at 3 months (OR 1.25; ), mother smoking more than once a day (; ), and father smoking at least once a day (OR 1.41; ). Compared to fathers who had 12+ years of school completion, having fathers who completed year 9 or lower was also a predictor of children with ear infection (; ).

Prevalence and cross-sectional bivariate association between ear infection and other health related morbidities were reported in Table 2. At the age of 4 to 5 years, ear infection was statistically associated with asthma (OR 1.55; ), headache (OR 3.59; ), other physical disabilities (OR 2.40; ), other illnesses (OR 1.87; ), and other infections (OR 3.87; ). By the age of 10 to 11 year, ear infection was statistically associated with asthma (OR 1.67; ), headache (OR 2.13; ), and tonsillitis (OR 4.67; ).

Table 2: Prevalence and cross-sectional association between ear infection and other health conditions.

Health conditions
Children aged 4 to 5 years
Children aged 10 to 11 years

% ()
Ear infection % prevalence ()
Odds ratios and value
% ()
Ear infection % prevalence ()
Odds ratios and value

Asthma

    No

7.2 (283)
OR = 1.00

2.7 (76)
OR = 1.00

    Yes
20.6 (1029)
10.7 (110)
OR  =  1.55 

P   <  0.001
33.2 (1381)
4.5 (62)
OR  =  1.67 

P   =  0.003

Headache

    No

7.8 (387)
OR = 1.00

3.1 (123)
OR = 1.00

    Yes
0.6 (30)
23.3 (7)
OR  =  3.59 

P   =  0.003
6.0 (248)
6.5 (16)
OR  =  2.13 

P   =  0.006

Tonsillitis

    No

3.0 (123)
OR = 1.00

    Yes

N/A

3.0 (125)
12.8 (16)
OR  =  4.67 

P   <  0.001

Vision problems

    No

7.8 (377)
OR = 1.00

3.1 (108)
OR = 1.00

    Yes
2.9 (146)
11.6 (17)
OR = 1.56

= 0.092
16.5 (687)
4.5 (31)
OR = 1.47

= 0.063

Other physical disabilities

    No

7.7 (375)
OR = 1.00

    Yes
2.3 (114)
16.7 (19)
OR  =  2.40 

P   =  0.001

N/A

Other illnesses

    No

7.6 (361)
OR = 1.00

3.2 (128)
OR = 1.00

    Yes
5.0 (247)
13.4 (33)
OR  =  1.87 

P   =  0.001
4.8 (198)
5.6 (11)
OR = 1.76

= 0.079

Other infections

    No

7.5 (366)
OR = 1.00

3.3 (138)
OR = 1.00

    Yes
2.4 (117)
23.9 (28)
OR  =  3.87 

P   <  0.001
0.6 (27)
3.7 (1)
OR = 1.14

= 0.916

Table 3 reports on prevalence and association between ear infection and overall health service usage. At the age of 4 to 5 years, ear infection was strongly and statistically significantly associated with the use of hospital outpatient clinics (OR 2.08; ) and the use of speech therapy (OR 1.79; ). By the age of 10 to 11 years, ear infection was found to be strongly and statistically significantly associated with the use of speech therapy (OR 3.24; ), early intervention service (OR 3.08; ), general practitioners (OR 2.76; ), and other specialists (OR 2.12; ).

Table 3: Prevalence and cross-sectional association between ear infection and health service use.

Health services
Children aged 4 to 5 years
Children aged 10 to 11 years

% ()
Ear infection % prevalence ()
Odds ratios and value
% ()
Ear infection % prevalence ()
Odds ratios and value

General practitioners

    No

6.2 (66)
OR = 1.00

1.6 (26)
OR = 1.00

    Yes
63.2% (3115)
8.4 (263)
OR  =  1.38;  

P   =  0.022
61.8% (2573)
4.4 (113)
OR  =  2.76; 

P   <  0.001

Hospital outpatients

    No

7.2 (272)
OR = 1.00

3.2 (127)
OR = 1.00

    Yes
8.3% (409)
13.9 (57)
OR  =  2.08;  

P   <  0.001
5.6% (231)
5.2 (12)
OR = 1.64;

Pediatrician

    No

3.2 (124)
OR = 1.00

    Yes

N/A

6.3% (264)
5.7 (15)
OR  =  1.83;  

P   =  0.031

Early intervention services

    No

7.7 (280)
OR = 1.00

3.2 (133)
OR = 1.00

    Yes
8.3% (415)
9.1 (49)
OR = 1.20;

1.5% (64)
9.4 (6)
OR  =  3.08;  

P   =  0.010

Speech therapy

    No

7.3 (266)
OR = 1.00

3.2 (128)
OR = 1.00

    Yes
10.9% (538)
12.3 (63)
OR  =  1.79;  

P   <  0.001
10.4% (513)
9.6 (11)
OR  =  3.24;  

P   <  0.001

Other specialist

    No

3.0 (109)
OR = 1.00

    Yes

N/A

11.8% (492)
6.1 (30)
OR  =  2.12;  

P   <  0.001

We also applied backward stepwise regression () to determine association between ear infection and overall health service use (data not shown) and found that among children aged 4 to 5 years, ear infection was statistically significantly associated with hospital outpatient clinic usage (OR 2.00; ) and the use of speech therapy (OR 1.71; ). Among children aged 10 to 11 years, ear infection was statistically significantly associated with the use of speech therapy (OR 2.70; ), general practitioners (OR 2.55; ), and other specialists (OR 1.72; ).

4. Discussion

This paper reports on two cross-sectional analyses of Australian children in 2004 (4 to 5 years) and in 2010 (10 to 11 years) of reported ear infection and their associated prevalence with the potential risk factors, health related comorbidity, and overall health service usage. Our prevalence of ear infection was 7.9% among children aged 4 to 5 years and 3.3% among children aged 10 to 11 years. Incidence and prevalence rate of ear infections varied depending on age groups (highest in the first three years); however, differences in definitions and diagnostic measures make comparisons between studies very difficult [16, 18, 28]. For example, a US study of children aged 1–8 years using weekly otoscopy reported prevalence ranging from 7–30% for children aged 5 years and above. Another study was a longitudinal study of Danish children which reported type B tympanogram point prevalence between 11 and 18% at ages 2–5 years and about 7% at ages 6 and 7 years.

Our study was based on parent-reported data which generally gives lower prevalence than other objective measures; however, our prevalence corresponds to the overall prevalence of ear infection from national data. For example, the National Aboriginal and Torres Strait Islander Health Survey 2004-2005 of the Australian Bureau of Statistics found that among children aged 0–14 years, 4% of indigenous children and 2% of nonindigenous children reported ear infection as a long-term medical condition [29]. In addition, a comprehensive report by Access Economics which analysed Bettering the Evaluation and Care of Health (BEACH) data reported that between 2006 and 2007, 11.5% of children aged less than 15 years had cases of ear infections managed by Australian general practitioners [30].

We acknowledge the possible limitation of parent-reported ear infections on behalf of children, including lack of severity reported as well as possible recall bias which may underreport the magnitude of ear infections and which does not take into account repeated ear infection episodes within the same year. However, the use of parent-reported data is not uncommon in international literature. For example, a recent population-based study in Scandinavia has shown self-reported otitis media to be relatively reliable and suggested that any inconsistency in reporting is likely to be associated with less severe episodes [31]. As well, a US study has reported that one of the most common methods to diagnose hearing loss among children was from parental concerns followed by school hearing screens [32].

We found various health conditions to be associated with ear infection at the age of 4 to 5 years but only asthma, headache, and tonsillitis were statistically significant at the age of 10 to 11 years. Other studies have also reported upper respiratory tract infections, including otitis media as being comorbid with other symptoms which could further concern the children and their family [14, 15]. However, we note the cross-sectional nature of our study which only allows possible associations to be found, but no causations can be inferred.

The main strength of this study is the use of the Longitudinal Study of Australian Children which includes a wide array of baseline and repeated questions and its large sample [21, 22]. Our study reported sociodemographic risk factors associated with ear infection to be indigenous status, not being breastfed, parent smoking, and lack of fathers’ education. Our findings on risk factors of ear infection are consistent with previous findings elsewhere [8, 9, 11, 33]. A study of 2512 children in North Finland (average age up to 2 years) also confirmed parental smoking, and lack of breastfeeding to be risk factors for ear infection [34]. An Australian longitudinal study of children under the age of 2 years (100 Aboriginal and 180 non-Aboriginal children) showed crowding, attending daycare, and lack of breastfeeding to be strong predictors of otitis media-related bacteria [35].

Despite the limitations of the data, we consistently found children with ear infection to be twice as likely to use general practitioners, pediatricians, and other specialists at the age of 10 to 11 years compared to children with no ear infection of the same age group. Our findings on the use of speech therapy and early intervention services show that their use is three times more likely among children with ear infection at the age of 10 and 11 years which could result from referral to the use of specialized services. These results suggest the implications on speech and communication as well as educational development [1, 2]. This study responds to a public health call for evidence on ear infection in Australia [18, 20]. We have provided consistent evidence pointing to the confirmed and identified risk factors, health related comorbidity, and a demand for health and social services required by children affected by ear infection.

Ethical Approval

The Longitudinal Study of Australian Children was approved by the Australian Institute of Family Studies Human Research Ethics Committee. License for data use was obtained via a written application to the Commonwealth of Australia as represented by the Department of Families, Housing, Community Services and Indigenous Affairs.

Acknowledgments

This study is supported by an unconditional grant from the GlaxoSmithKline. The authors used confidentialised unit record from Growing Up in Australia—the Longitudinal Study of Australian Children (LSAC). The study has been conducted in partnership between the Australian Government Department of Families, Housing, Community Services and Indigenous Affairs (FaHCSIA), the Australian Institute of Family Studies (AIFS), and the Australian Bureau of Statistics (ABS). The findings and views reported in this paper are those of the authors and should not be attributed to FaHCSIA, AIFS or the ABS. Comments from reviewer(s) were greatly appreciated. The authors also thank Peter Sbirakos for editorial support with the paper revision.

References

J. E. Roberts, R. M. Rosenfeld, and S. A. Zeisel, “Otitis media and speech and language: a meta-analysis of prospective studies,” Pediatrics, vol. 113, no. 3, pp. e238–e248, 2004.

J. A. Thorne, “Middle ear problems in Aboriginal school children cause developmental and educational concerns,” Contemporary Nurse, vol. 16, no. 1-2, pp. 145–150, 2003.

P. W. Zinkus, M. I. Gottlieb, and M. Schapiro, “Developmental and psychoeducational sequelae of chronic otitis media,” American Journal of Diseases of Children, vol. 132, no. 11, pp. 1100–1104, 1978.

I. Baumann, B. Gerendas, P. K. Plinkert, and M. Praetorius, “General and disease-specific quality of life in patients with chronic suppurative otitis media—a prospective study,” Health and Quality of Life Outcomes, vol. 9, article 48, 2011.

C. N. M. Brouwer, A. R. Maillé, M. M. Rovers, D. E. Grobbee, E. A. M. Sanders, and A. G. M. Schilder, “Health-related quality of life in children with otitis media,” International Journal of Pediatric Otorhinolaryngology, vol. 69, no. 8, pp. 1031–1041, 2005.

V. Yiengprugsawan, A. Hogan, and L. Strazdins, “Longitudinal analysis of ear infection and hearing impairment: findings from 6-year prospective cohorts of Australian children,” BMC Pediatrics, vol. 13, no. 1, article 28, 2013.

A. Hogan, M. Shipley, L. Strazdins, A. Purcell, and E. Baker, “Communication and behavioural disorders among children with hearing loss increases risk of mental health disorders,” Australian and New Zealand Journal of Public Health, vol. 35, no. 4, pp. 377–383, 2011.

I. J. M. Dhooge, “Risk factors for the development of otitis media,” Current Allergy and Asthma Reports, vol. 3, no. 4, pp. 321–325, 2003.

M. M. Rovers, I. M. C. M. de Kok, and A. G. M. Schilder, “Risk factors for otitis media: an international perspective,” International Journal of Pediatric Otorhinolaryngology, vol. 70, no. 7, pp. 1251–1256, 2006.

N. M. P. Hetzner, R. A. Razza, L. M. Malone, and J. Brooks-Gunn, “Associations among feeding behaviors during infancy and child illness at two years,” Maternal and Child Health Journal, vol. 13, no. 6, pp. 795–805, 2009.

T. W. Morrissey, “Multiple child care arrangements and common communicable illnesses in children aged 3 to 54 months,” Maternal and Child Health Journal, 2012.

E. A. MacIntyre, C. J. Karr, M. Koehoorn et al., “Otitis media incidence and risk factors in a population-based birth cohort,” Paediatrics and Child Health, vol. 15, no. 7, pp. 437–442, 2010.

K. Kong and H. L. C. Coates, “Natural history, definitions, risk factors and burden of otitis media,” Medical Journal of Australia, vol. 191, no. 9, supplement, pp. S39–S43, 2009.

P. S. Morris, “Upper respiratory tract infections (including otitis media),” Pediatric Clinics of North America, vol. 56, no. 1, pp. 101–117, 2009.

G. Karevold, E. Kvestad, P. Nafstad, and K. J. Kværner, “Respiratory infections in schoolchildren: co-morbidity and risk factors,” Archives of Disease in Childhood, vol. 91, no. 5, pp. 391–395, 2006.

T. E. O'Connor, C. F. Perry, and F. J. Lannigan, “Complications of otitis media in indigenous and non-Indigenous children,” Medical Journal of Australia, vol. 191, no. 9, supplement, pp. S60–S64, 2009.

P. S. Morris, A. J. Leach, P. Silberberg et al., “Otitis media in young Aboriginal children from remote communities in Northern and Central Australia: a cross-sectional survey,” BMC Pediatrics, vol. 5, article 27, 2005.

H. Gunasekera, P. S. Morris, J. Daniels, S. Couzos, and J. C. Craig, “Otitis media in Aboriginal children: the discordance between burden of illness and access to services in rural/remote and urban Australia,” Journal of Paediatrics and Child Health, vol. 45, no. 7-8, pp. 425–430, 2009.

L.-A. S. Kirkham, S. P. Wiertsema, H. C. Smith-Vaughan et al., “Are you listening? The inaugural Australian Otitis Media (OMOZ) workshop—towards a better understanding of otitis media,” Medical Journal of Australia, vol. 193, no. 10, pp. 569–571, 2010.

P. S. Morris, P. Richmond, D. Lehmann, A. J. Leach, H. Gunasekera, and H. L. C. Coates, “New horizons: otitis media research in Australia,” Medical Journal of Australia, vol. 191, no. 9, supplement, pp. S73–S77, 2009.

M. Gray and D. Smart, “Growing Up in Australia. The Longitudinal Study of Australian Children is now walking and talking,” Family Matters, vol. 79, pp. 5–13, 2008.

J. M. Nicholson and A. Sanson, “A new longitudinal study of the health and wellbeing of Australian children: how will it help?” Medical Journal of Australia, vol. 178, no. 6, pp. 282–284, 2003.

S. Misson and M. Sipthorp, “Wave 2 weighting and non-response,” LSAC Technical Paper 5, Australian Institute of Family Studies, Melbourne, Australia, 2005.

A. Sanson, S. Misson, M. Wake, et al., “Summarising children’s wellbeing: the LSAC Outcome Index,” LSAC Technical Paper 2, Australian Institute of Family Studies, Melbourne, Australia, 2005.

C. Soloff, D. Lawrence, M. Sebastian, and R. Johnstone, “Wave 1 weighting and non-response,” LSAC Technical Paper 3, Australian Institute of Family Studies, Melbourne, Australia, 2006.

ABS, “An Introduction to Socio-Economic Indexes for Areas (SEIFA) ABS Catalogue Number 2039.0,” Commonwealth of Australia: Australian Bureau of Statistics, 2006

StataCorp, “Stata 12.0 for Windows,” College Station, Tex, USA, Stata Corporation, 2011

R. Rosenfeld and C. Bluestone, Evidence-Based Otitis Media, BC Decker, Hamilton, Ontario, Canada, 2003.

ABS, “National Aboriginal and Torres Strait Islander Health Survey, Australia, 2004-05,” ABS Catalogue Number 4715.0. Canberra, Australia, Australian Bureau of Statistics, 2006

Access Economics, The cost burden of otitis media in Australia, Access Economics Pty Limited, GlaxoSmithKline, The Department of Otolaryngology, Head and Neck Surgery, Princess Margaret Hospital for Children, Perth, Australia, 2008.

E. Kvestad, K. J. Kværner, E. Røysamb, K. Tambs, J. R. Harris, and P. Magnus, “The reliability of self-reported childhood otitis media by adults,” International Journal of Pediatric Otorhinolaryngology, vol. 70, no. 4, pp. 597–602, 2006.

K. Dedhia, D. Kitsko, D. Sabo, and D. H. Chi, “Children with sensorineural hearing loss after passing the newborn hearing screen,” JAMA Otolaryngology-Head & Neck Surgery, vol. 139, pp. 119–123, 2013.

M. Uhari, K. Mäntysaari, and M. Niemelä, “A meta-analytic review of the risk factors for acute otitis media,” Clinical Infectious Diseases, vol. 22, no. 6, pp. 1079–1083, 1996.

O.-P. Alho, E. Läärä, and O. Hannu, “How should relative risk estimates for acute otitis media in children aged less than 2 years be perceived?” Journal of Clinical Epidemiology, vol. 49, no. 1, pp. 9–14, 1996.

P. Jacoby, K. S. Carville, G. Hall et al., “Crowding and other strong predictors of upper respiratory tract carriage of otitis media-related bacteria in Australian aboriginal and non-aboriginal children,” Pediatric Infectious Disease Journal, vol. 30, no. 6, pp. 480–485, 2011.