Retrospective cross-sectional study on bronchiectasis in adult Aboriginal Australians: disease characteristics and comparison with ethnically diverse global bronchiectasis registry cohorts

Introduction

Bronchiectasis is a chronic respiratory condition that clinically manifests as chronic productive cough secondary to recurrent respiratory tract infection/inflammation and radiologically characterised by dilation of bronchial airways.1 Bronchiectasis, once thought to be a rare disorder, is progressively gaining attention and being recognised as one of the major causes for chronic ill health among diverse ethnic populations.2 3 Moreover, evidence in the literature suggests that there is substantial heterogeneity and geographic variation in the prevalence and in the clinical manifestations of bronchiectasis across various ethnic and socioeconomic groups.3

In line with what is being observed globally among cohorts of various ethnicities, there is growing evidence to suggest that bronchiectasis is not only common in the paediatric Indigenous population, but also prevalent among adult Indigenous people.4 Prevalences among both groups are higher compared with non-Indigenous populations, including among Aboriginal Australians4 (from here on ‘Indigenous’ is used to refer to global First Nations populations, while ‘Aboriginal Australian’ is used to specifically refer to Australia’s First Nations population). Moreover, adult Aboriginal Australians are also reported to have a higher prevalence of multimorbidity, 2.6 times higher than that for non-Aboriginal people.5 Complex and advanced respiratory disorders are also highly prevalent in this population, giving rise to higher hospital admission rates and mortality.6–8 Previous studies in other global cohorts have illustrated higher overall morbidity and worse outcomes when bronchiectasis is coupled with multimorbidity, more specifically in the presence of concurrent respiratory disorders, such as chronic obstructive pulmonary disease (COPD) and with reduced lung function parameters.9 In the adult Aboriginal Australian population, multimorbidity, particularly of concurrent respiratory diseases, alongside reduced lung function parameters is highly prevalent.6 10 11 Furthermore, significant sex differences in the clinical manifestation of respiratory diseases have been noted in this population.12

Nevertheless, in recent years, there have been collaborative efforts from several countries and across continents to establish bronchiectasis registries in order to address the disease burden among adult populations.13 These registries have reported valuable clinical data, including health-related outcomes secondary to bronchiectasis across various global geographic regions and diverse ethnic populations.14–18 However, representation of Indigenous people in these bronchiectasis registries remains sparse, including in the first report from the Australian bronchiectasis registry (1 (0.2%)).15 This is despite the high prevalence of chronic respiratory comorbidities, and socio-economic barriers to healthcare experienced by Indigenous populations.19 Hence, in light of recent literature on international cohorts with bronchiectasis, it is timely for an insight to describe and compare the bronchiectasis disease profile among an Indigenous cohort against the global cohorts.14–18 Therefore, this study aims to comprehensively assess various clinical parameters among an adult Aboriginal Australian cohort diagnosed to have bronchiectasis over a 10-year period (2011–2020) from the Top End Health Service (TEHS) region of the Northern Territory (NT) of Australia and compare against other published bronchiectasis registry data.

Methods

Study population

Approximately 3.3% of Australians self-identify as Aboriginal and/or Torres Strait Islanders. The NT is an Australian federal territory occupying the central-northern region of Australia. The TEHS region within the NT covers approximately 35% or 4 75 338 km² of the total area of the NT and contains an estimated adult population (>18 years) of 129 000 people, representing almost 80% of the total NT adult population (figure 1).20 21 In the TEHS region, 22% of the adult population are Aboriginal Australians, of whom approximately 77% reside in remote or very remote communities as defined by the Australian Statistical Geographic Standard Level 4 or Level 5.22

Figure 1

Request permission

Map showcasing the four health regions in the TEHS, NT, Australia, alongside the total Aboriginal Australian population and number (%) of females for each region as per 2021 ABS census data. Approximate location of hospitals is notated with ‘H’. ABS, Australian Bureau of Statistics; H, Hospital; NT, Northern Territory; TEHS, Top End Health Service.

Results

Chest CT scan data

The most common location of bronchiectasis was noted to involve the left lower lobe (73%) followed by the right lower lobe (62%), with the left upper lobe the least commonly affected (22%) (figure 2). Females were recorded to have the right middle lobe affected significantly more often than males (50 vs 34%, p=0.001, power=0.935). Bilateral involvement was observed in 73% of patients with no significant difference between sexes. Most patients (73%) had two or more lobes affected, and 36% of patients had three or more lobes affected.

Figure 2

Request permission

CT scan data for females (white numerals) and males (black numerals). LLL, left lower lobe; LUL, left upper lobe; RLL, right lower lobe; RML, right middle lobe; RUL, right upper lobe.

Sputum microbiology results

Sputum cultures results were available for 425 (93%) study patients during the study window (figure 3). Haemophilus influenzae was the most common pathogen, isolated in 58%. Pseudomonas aeruginosa was identified in almost one-third (31%) of patients and Moraxella species in one quarter (26%). Minor non-significant sex differences were noted for the sputum microbiology; however, non-tuberculous mycobacterium were isolated in a significantly greater proportion of males than females (17% vs 8%, p=0.011 power=0.713).

Figure 3

Request permission

Sputum results for bronchiectasis patients split by sex with p values for differences between sexes (via χ² test or Fishers exact test) noted above each column. NTM, non-tuberculous mycobacterium; TB, tuberculosis.

Discussion

To the best of the authors’ knowledge, this is the first comprehensive study detailing clinical and laboratory parameters, including sex differences among an adult Aboriginal Australian population with bronchiectasis from the Top End, NT of Australia. This study demonstrates that the Aboriginal Australian population with bronchiectasis is significantly younger than the non-Aboriginal Australian cohort and most other international cohorts. However, the proportion of females is comparable as found among other reports, as is the median BMI. In our study, patients with bronchiectasis were a median 56 years of age, with only a slight (55%) female predominance. In contrast, the ABR data which predominantly consisted of a non-Aboriginal Australians reported a median age of 71 years with 71% female,15 and the European EMBARC cohort reported a median age of 67 years with 61% female.14

Earlier literature has demonstrated differences in the way bronchiectasis manifests between male and females which has been attributed to the effects of sex hormone and lung microbiomes.25 26 Previous registry data have not elaborated on disease manifestations between sexes in detail. Although in our study we observed differences between sexes on some clinical parameters, there was no substantial clinically relevant differences, other than lower absolute lung function values among females compared with males. Overall, spirometry parameters showed significantly reduced values, with a median FEV₁ of 38% predicted, compared with 61 to 77% predicted in other registry cohorts.14–17 In the TEHS, NT region, adult Aboriginal Australians with respiratory disorders are observed to have substantially lower lung function values in comparisons to their non-Indigenous counterparts.27–32 Previous studies have shown that presence of reduced lung function parameters is associated with long-term poor outcomes among patients with bronchiectasis.33–36 Whether this is also the case for Indigenous patients is currently not known, particularly in the absence of any published longitudinal data.

Presence of multimorbidity alongside bronchiectasis is associated with greater risk of adverse outcomes.37 Indeed, presence of multimorbidity has been reported to be highly prevalent among Aboriginal Australians.38–50 This study mirrored these previous reports, as presence of multimorbidity was significantly higher among the Aboriginal Australian cohort, with almost half reporting cardiovascular disease or diabetes mellitus, and four in five reporting COPD, which is significantly higher than reported in both international cohorts,14 16–18 and the Australian non-Aboriginal cohort.15 Similarly, the presence of a smoking history was significantly greater, with 85% of the Aboriginal cohort reporting a smoking history compared with 22–46% among other registry reports.14–18 A more recent follow-up study from the EMBARC-Indian registry data has shown worse outcomes and mortality among bronchiectasis patients with a smoking history and comorbid COPD.51 It is highly plausible this could be similar among Aboriginal Australians with a high prevalence of smoking and concurrent presence of COPD and bronchiectasis.52–55 However, further prospective studies will be needed to investigate this association in this population.

In relation to sputum microbiology, in contrast to each of the other registry cohorts, where P. aeruginosa was the most commonly cultured bacterial pathogen, within our study, H. influenzae was the most common pathogen cultured (58%), followed by Streptococcus pneumoniae (32%). Although P. aeruginosa was not the most commonly cultured, it was still cultured significantly more commonly within this cohort (31%) compared with the ABR (19%), EMBARC-Europe (18%), EMBARC-India (14%) and KMBARC (11%).14–17 Nonetheless, there are limited data in relation to sputum microbiology among adult Aboriginal Australian patients with bronchiectasis and its relationship with other health related outcomes.4 However, studies from Central Australian region where human T-lymphotropic virus infection is reported to have strong association with bronchiectasis among Aboriginal patients,.56–58 This may indicate that there may be several differing geographical factors either intrinsic or extrinsic that may be influencing the occurrence and progression of bronchiectasis among Indigenous people.

To assess the severity and prognosis among patients with bronchiectasis, two well established tools are often used: the FACED tool (F, forced expiratory volume in 1 s; A, age; C, chronic colonisation by P. aeruginosa; E, radiological extension; D, dyspnoea) and the BSI tool.59 60 Due to our study being retrospective in nature and lacking some of the required parameters, especially the Modified Medical Research Council Dyspnoea Scale61 to accurately assess the severity and prognosis using either the FACED or BSI tools, we were unable to compare our data to assess the bronchiectasis severity to other registry cohorts in more detail. However, the applicability of these tools for an Indigenous population is questionable, as these tools were developed from non-Indigenous population data sets. For example, age, which is the single highest scoring contributor to the BSI, presents a problem for the Indigenous population, which is significantly younger, in our study cohort—31% of the study patients would scores ‘0’ due to being <50 years and a further 56% score ‘2’ due to being aged 50–69 years—hence, Indigenous people may spuriously demonstrate lower BSI scores. This is despite higher prevalence of comorbidities, higher smoking rates, significantly reduced lung function, greater array of organisms cultured and higher hospital admissions. Moreover, impaired access to radiology (CT) and comprehensive lung function testing among Indigenous patients residing in remote and rural communities further limit the utilisation of the BSI and FACED tools, and more broadly, substantial chest radiology (CT) data is lacking among the Aboriginal Australian populations.7 62 As observed in this study, only 169 patients (37%) had both FEV₁ and BMI data available. Hence, it is reasonable to speculate that use of these tools would potentially lead to inappropriate classification of disease severity and may also give way for inappropriate therapeutic interventions as well.63 64 Therefore, there is a need for developing bronchiectasis severity tool using differing clinical parameters specific for Indigenous populations, in addition to considering realistic limitations of remoteness and cultural factors.65 66

Although current literature portrays a high bronchiectasis disease burden and associated adverse health outcomes globally,67 innovative preventative or therapeutic interventions are negligible, other than the proven benefits of chest physiotherapy/airway clearance techniques.68 Indeed, a recent study from Taiwan has demonstrated that the only factor that reduced mortality risk was airway clearance therapy.69 Ironically, implementation of chest physiotherapy/airway clearance interventions and availability of such dedicated services for Aboriginal Australian people is sparse currently, especially among those residing in remote and rural communities.70 However, use of inhaled pharmacotherapy was noted to be substantial, especially prescription of ICS in our study patients, similar as observed in the ABR report among non-Aboriginal Australians.71 This is despite guidelines advocating cautious use of ICS among patients with bronchiectasis.72 73 The risk of pneumonia associated with ICS use and the unknown potential effects ICS may have on the microbiome in Aboriginal patients with bronchiectasis is of concern.

In the previously published registry reports,14–18 other than the ABR data which has clearly represented inclusion of Aboriginal Australians (although with far lesser numbers (1 (0.2%, (not inclusive of or overlapping with our current study data)), in comparison to non-Aboriginal patients), it is unclear if the other international reports from the USA, Europe, Korea and India included any Indigenous patients. Yet, Indigenous people reside in these aforementioned geographic regions, such as the Yukon Kuskokwin delta in Alaska, USA; in northern Europe the “Sámi’ People; in the Korean Peninsula the ‘Jeju’ people; and in India the tribal people ‘Adivasis’ among other diverse cultural groups.4 It is estimated that over 476 million Indigenous peoples live worldwide and make up approximately six per cent of the global population. There is also significant disparity in several social determinants, and Indigenous peoples’ life expectancy is up to 20 years lower than that of non-Indigenous people.74 It is a matter of speculation how much of this heightened mortality and reduced life expectancy experienced by underprivileged global Indigenous people would be secondary to respiratory disorders such as bronchiectasis.

Nevertheless, this study has demonstrated that the bronchiectasis disease burden is substantial as is its impact on overall health and well-being among adult Aboriginal Australians, much higher than International and non-Aboriginal cohorts. Moreover, unlike among non-Indigenous populations where bronchiectasis is predominantly noted to occur in adulthood and with advancing age, among Aboriginal Australians, there is a significant incidence of bronchiectasis in childhood.75 It may be reasonable to speculate that Indigenous children transiting into adulthood with ongoing recurrent exacerbations which perpetuate airway inflammation contributes to the deterioration in airway function, hence the aftermath of the disease course in the adulthood.76 77 Therefore, further dedicated efforts are needed to address this disparity to reduce the morbidity and mortality secondary to bronchiectasis, including implementing educational programmes and facilitating transition of care from paediatric care to adulthood.78 79 To this vein, it is paramount for health organisations and stakeholders to consider establishing a national and international task force consisting of adult respiratory and paediatric physicians, researchers, primary health medical practitioners, physiotherapists, community Aboriginal health workers and Aboriginal controlled community organisations to address the respiratory health burden among Aboriginal Australians and Indigenous people globally. This will not only enable Aboriginal Australian and global Indigenous people to lead a better quality of life, but also reduce the economic cost and healthcare utilisation related to the significant bronchiectasis burden.

Conclusion

The Aboriginal Australian bronchiectasis cohort in our study had more multimorbidity, including concurrent respiratory comorbidities, alongside reduced lung function parameters, differing sputum microbiology, including demonstrating multilobe and bilateral disease burden on chest CT in comparison to ethnically diverse national and international comparison cohorts. Further dedicated efforts are needed to address this disparity and to close the respiratory health gap not only among the Aboriginal Australians, but also Indigenous populations globally.