Influence of Interstitial Lung Disease on Systemic Sclerosis Hospitalizations, A National Study (2002-2020)

doi:10.21203/rs.3.rs-4614031/v1

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Influence of Interstitial Lung Disease on Systemic Sclerosis Hospitalizations, A National Study (2002-2020)

https://doi.org/10.21203/rs.3.rs-4614031/v1

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Systemic sclerosis (SSc) is an autoimmune connective tissue disorder that can cause generalized inflammation and is characterized by fibrosis of the skin, organs and vasculopathy. Limited SSc is more common and typically less serious and less frequent diffuse has a higher mortality rate due to end organ damage. One of the most common complications of SSc is interstitial lung disease (ILD). ILD is characterized by fibrosis, scarring, and inflammation of the lungs. ILD has a 30% prevalence and a 40% 10-year mortality in patients with SSc worldwide. Hospitalizations for SSc were abstracted from the 2002–2020 using the National Inpatient Sample (NIS), an all-payer administrative database in capturing 97% of hospital discharges in the Untied States. The primary aim was to evaluate whether in-patient mortality, length of stay (LOS), and hospital cost differed if SSc patients had underlying ILD. We estimated multivariable logistic regression and log-normal models controlling for age, biological sex, race/ethnicity, income, and hospital setting. ILD was associated with 88% greater adjusted odds of in-patient mortality (aOR 95% CI: 1.53 to 2.31, p < 0.001), 15% longer stays (aOR 95% CI: 1.04 to 1.28, p = 0.000), and 33% higher adjusted hospital costs (aOR 95% CI: 1.26 to 1.40, p < 0.001). These findings concluded that SSc with ILD has a significant impact on hospitalization outcomes.

Systemic Sclerosis

Interstitial lung disease

Mortality

Length of stay

Hospitalizations

Healthcare costs

National

Inpatient

Sample

Systemic sclerosis (SSc) is an autoimmune connective tissue disease, characterized by dysfunction of the immune system leading to gradual fibrosis of the skin and other organs.¹ It is a rare disease with a higher prevalence in young, middle-aged women.² SSc is characterized as limited and diffuse. Limited SSc has a greater prevalence and is typically less serious as it generally does not involve visceral organ systems. Diffuse SSc is occurs less frequently and is associated with higher mortality as it often involves the heart, lungs, and kidneys. Diffuse SSc is more commonly associated with interstitial lung disease (ILD). ILD is the leading cause of death in patients with SSc with an estimated prevalence of 30% and 10-year mortality of 40%.². In the United States, the crude incidence of isolated SSc was 16.4 per 100,000 patient population compared to SSc with ILD (SSc-ILD) with a crude incidence of and 1.2 per 100,000 patient population. ⁵ Similarly, the prevalence of isolated SSc was 24.4 per 100,000 patient population compared to 6.9 per 100,000 patient population for SSc-ILD.⁵ ILD commonly presents with vague respiratory symptoms such as dyspnea on exertion and dry cough. Given the aforementioned prevalence and mortality of SSc-ILD, it is critical to diagnose and treat SSc-ILD in early stages of disease.

Patients suffering from SSc and ILD make up a significant amount of healthcare costs³. Previous research found that hospitalized patients with SSc-ILD have an average length of stay (LOS) of 6.5 days³. A prior retrospective study on patients hospitalized at the University of Michigan from 2011–2019 demonstrated that the average cost for the management of SSc-ILD was $191,107 as compared to $101,839 for isolated SSc. Prior retrospective observational studies comparing patients with isolated SSc and SSc-ILD have been critical in establishing a relationship between systemic sclerosis and ILD as well as examining how morbidity and mortality are impacted by that relationship³. Our study aims to take that research one step further by identifying hospitalizations specifically for SSc and evaluating the association of ILD on hospitalization outcomes using a national database. The research will provide imperative information about mortality and healthcare utilization associated with isolated SSc and SSc-ILD. Notably, previous studies focused on differences between isolated ILD and SSc-ILD at single institution and this study utilizes the nationally representative National Inpatient Sample (NIS) to provide generalizable, US-specific findings.

We believe this will provide specific and insightful information about how ILD impacts hospitalizations, as well as the overall burden on the healthcare system. We investigated ILD specifically because previous studies demonstrated an immense impact and healthcare cost associated with general lung involvement in patients with SSc⁴. The aim is to uncover more focused information on the impact of hospitalizations for SSc with and without ILD and how that relates to the healthcare burden. To provide a comprehensive understanding of how the presence of ILD affects SSc hospitalization outcomes, we assessed between-ILD differences in inpatient mortality, LOS, and hospital cost irrespective of whether the patients experienced ILD-specific complications.

Data source

Data were abstracted from the 2002–2020 National Inpatient Sample (NIS). The NIS is an all-payer, administrative inpatient care database. The Agency for Healthcare Research and Quality (AHRQ) sponsors the NIS along with the other Healthcare Cost and Utilization Project (HCUP) databases.¹³ The NIS covers over 97% of the US population and estimates approximately 35 million hospital discharges per year¹³. Importantly, the NIS is de-identified and HIPAA compliant. Creighton University's Institutional Review Board acknowledged this study as Not Human Subjects Research (InfoEd record number: 2004587). The NIS is publicly available; information about purchasing the NIS can be found at: https://hcup-us.ahrq.gov/tech_assist/centdist.jsp

Aim

The primary aim of the study was to evaluate whether inpatient mortality, LOS, and hospital cost differed by whether the patient suffered from ILD in hospitalizations for SSc. Additionally, we evaluated if age, biological sex, race/ethnicity, and hospital setting moderated the effect of ILD on these outcomes.

Cohort Identification

Hospitalizations for SSc were identified using the hospitalization's primary diagnosis code. From January 2002 through September 2015, International Classification of Disease, Ninth Revision (ICD-9: 710.1) codes were used. From October 2015 through December 2020, International Classification of Diseases, Tenth Revision (ICD-10: M34) codes were used. Next, among thehospitalizations for SSc, we stratified by whether the hospitalization also carried a diagnosis for ILD (ICD-9: 517.2; ICD-10: M34.81). Hospitalizations of patients younger than 18 years were excluded.

Descriptives

To describe the study cohort, we identified patient- and facility-level descriptives. Patient-level descriptives included age, biological sex (male, female), race/ethnicity (White, Black, Hispanic, other), income quartile (I, II, III, IV), and insurance type (Medicare, Medicaid, private, other). Facility-level descriptives included region (Northeast, Midwest, South, West), bed size (small, medium, large), and facility type (rural, urban nonteaching, urban teaching). These descriptives were presented overall and stratified by whether the SSc hospitalization also carried a diagnosis of ILD. Categorical descriptives were presented as percent and compared via Rao-Scott chi-square tests. Continuous descriptives were presented as median and interquartile range and compared using regression.

Statistical Analysis

To evaluate the association between concomitant ILD and inpatient mortality, we estimated a logistic regression model. We estimated log-normal regression models to evaluate the association between 1) concomitant ILD and LOS and 2) concomitant ILD and cost. Cost was inflation adjusted to mid-year 2020 US dollars¹⁴. Next, we assessed whether patient and facility factors (age, biological sex, race/ethnicity, facility type) moderated the effect of ILD on inpatient mortality, LOS, and cost using two-way interaction effects. For each factor we estimated an ILD-by- factor interaction effect (e.g., ILD-by-age, ILD-by-biological sex, etc.) in respective regression models.

The sampling design of the NIS was accounted for in all analyses. We evaluated the nonlinear functional form of age using restricted cubic splines with knots at the 10th, 50th, and 90th percentiles¹⁵. Statistical significance was indicated as two-tailed p < 0.05.

Cohort Descriptives

In the US from 2002 through 2020, there were an estimated 33,549 (95% CI: 31,613 − 35,485) hospitalizations for SSc; of those, 34.14% (N = 11,453, 95% CI: 10,554 − 12,351) also suffered from ILD. Cohort descriptives are presented in Table 1. Briefly, hospitalizations for SSc included patients that were commonly middle-aged, white, female, and insured through Medicare. Urban teaching facilities and facilities with a large bed size were the most frequent.

Table 1

Demographics of systemic sclerosis hospitalizations stratified by concomitant interstitial lung disease.
	Overall	ILD		p
	Overall	Yes	No	p
Age, median [interquartile range]	55.91 [45.56, 66.56]	56.27 [46.64, 66.26]	55.65 [44.69, 66.71]	0.006
Biological Sex, %
Male	19.98	21.94	18.97	0.007
Female	80.02	78.06	81.03	0.007
Race/ethnicity, %
White	57.94	55.18	59.38	0.018
Black	23.21	25.37	22.09
Hispanic	12.74	13.60	12.30
Other	6.10	5.85	6.23
Income Quartile, %
0-25th	26.03	26.30	25.90	0.299
26th-50th	23.88	22.35	24.67
51st-75th	23.10	23.71	22.78
76th-100th	26.99	27.64	26.65
Insurance, %
Medicare	45.74	46.61	45.29	0.483
Medicaid	13.34	13.04	13.50
Private	34.23	34.30	34.19
Other	6.69	6.05	7.02
Facility Region, %
Northeast	22.79	21.48	23.46	0.184
Midwest (North Central)	23.91	22.69	24.55
South	35.54	37.04	34.77
West	17.76	18.79	17.22
Facility Bed Size, %
Small	9.36	7.54	10.31	0.001
Medium	19.98	18.90	20.54
Large	70.66	73.56	69.15
Facility Type, %
Rural	6.43	4.87	7.25	0.003
Urban nonteaching	24.38	23.83	24.67
Urban teaching	69.19	71.30	68.09

In-patient mortality

Table 2 presents the unadjusted and adjusted odds of inpatient mortality by ILD status. After adjusting for age, sex, race/ethnicity, income quartile, and facility type, SSc-ILD was associated with 88% greater adjusted odds of inpatient mortality compared to isolated SSc (aOR: 1.88, 95% CI: 1.53 to 2.31, p < 0.001; Table 2). Age moderated the effect of ILD on inpatient mortality (interaction p = 0.021); as age increased the difference in mortality between SSc-ILD and isolated SSc decreased (Fig. 1). Biological sex, race/ethnicity, income quartile, and facility type did not moderate the effect of ILD on inpatient mortality (interaction p = 0.128, p = 0.222, p = 0.581, p = 0.524, respectively). In other words, the association between ILD and inpatient mortality did not vary based on biological sex, race/ethnicity, income quartile, or facility type; simple main effects are provided in Table 2.

Table 2

In-patient mortality by concomitant interstitial lung disease and demographic factors
	Unadjusted				Adjusted
	ILD: Yes	ILD: No	Ratio (95% CI)	p	Ratio (95% CI)	p
In-patient mortality, %	12.11	6.38	1.90 (1.55–2.32)	< 0.001	1.88 (1.53–2.31)	< 0.001
By age	Varied, see Supplemental Fig. 1			0.021	Varied, see Fig. 1	0.021
By biological sex				0.087		0.128
Female	13.32	5.94	2.07 (1.65–2.61)	< 0.001	2.05 (1.62–2.59)	< 0.001
Male	11.42	8.34	1.37 (0.90–2.08)	0.141	1.41 (0.93–2.15)	0.108
By race				0.218		0.222
White	14.01	7.20	2.15 (1.68–2.76)	< 0.001	2.10 (1.64–2.70)	< 0.001
Black	8.65	8.10	1.30 (0.85–1.98)	0.232	1.27 (0.82–1.95)	0.279
Hispanic	10.35	6.91	2.18 (1.19–4.01)	0.012	2.21 (1.20–4.08)	0.011
Other	14.13	10.97	1.89 (0.79–4.39)	0.152	1.83 (0.77–4.34)	0.169
Income quartile				0.569		0.581
I	11.36	6.69	1.70 (1.16–2.48)	0.006	1.69 (1.16–2.48)	0.007
II	12.28	5.24	2.34 (1.52–3.61)	< 0.001	2.31 (1.49–3.58)	< 0.001
III	12.39	5.94	2.09 (1.37–3.17)	0.001	2.10 (1.38–3.20)	< 0.001
IV	12.49	7.50	1.66 (1.17–2.37)	0.005	1.65 (1.15–2.35)	0.006
By facility type				0.557		0.524
Rural	7.48	6.42	1.17 (0.45–3.04)	0.754	1.11 (0.42–2.93)	0.830
Urban nonteaching	14.31	7.78	1.84 (1.28–2.64)	0.001	1.83 (1.27–2.63)	0.001
Urban teaching	11.74	5.88	1.99(1.55–2.57)	< 0.001	1.97 (1.53–2.55)	< 0.001

Length of Stay

Table 3 presents the unadjusted and adjusted LOS by ILD status. After adjusting for age, sex, race/ethnicity, income quartile, and facility type, SSc-ILD was associated with 15% longer hospital stays compared to isolated SSc (aOR: 1.15, 95% CI: 1.04 to 1.28, p = 0.008; Table 3). Age moderated the effect of ILD on LOS (interaction p < 0.001); in hospitalizations of young and middle-aged patients, LOS was longer in those suffering from ILD (Fig. 2). Biological sex also moderated the effect of ILD on LOS (interaction p = 0.047). Compared to isolated SSc, SSc-ILD was associated with longer hospital stays in female and male patients; in females SSc-ILD was associated with 11% longer adjusted stays and in males SSc-ILD was associated with 33% longer stays compared to isolated SSc (Female- aOR: 1.11, 95% CI: 1.01 to 1.23, p = 0.038; Male- aOR: 1.33, 95% CI: 1.09 to 1.63, p = 0.006, Table 3). Race/ethnicity, income quartile, and facility type did not moderate the effect of ILD on LOS (interaction p = 0.278, p = 0.243, p = 0.188, respectively); main effects are provided in Table 3.

Table 3

Length of stay by concomitant interstitial lung disease and demographic factors
	Unadjusted				Adjusted
	ILD: Yes	ILD: No	Ratio (95% CI)	p	Ratio (95% CI)	p
Length of stay, days	5.16	4.38	1.18 (1.06–1.31)	0.002	1.15 (1.04–1.28)	0.008
By age	Varied, see Supplemental Fig. 2			< 0.001	Varied, see Fig. 2	< 0.001
By biological sex				0.121		0.047
Female	5.06	4.42	1.14 (1.03–1.27)	0.009	1.11 (1.01–1.23)	0.038
Male	5.51	4.20	1.31 (1.08–1.60)	0.006	1.33 (1.09–1.63)	0.006
By race				0.322		0.278
White	5.00	4.10	1.22 (1.05–1.42)	0.010	1.20 (1.03–1.39)	0.020
Black	5.77	5.06	1.14 (1.01–1.29)	0.041	1.12 (0.98–1.27)	0.097
Hispanic	5.11	4.39	1.16 (1.05–1.29)	0.004	1.18 (1.06–1.31)	0.003
Other	4.35	4.87	0.89 (0.66–1.21)	0.461	0.88 (0.66–1.18)	0.417
Income quartile				0.210		0.243
I	5.31	4.73	1.12 (1.00-1.25)	0.042	1.08 (0.96–1.20)	0.197
II	5.39	4.43	1.22 (1.09–1.36)	0.001	1.19 (1.06–1.33)	0.002
III	5.17	4.89	1.06 (0.94–1.18)	0.333	1.05 (0.94–1.17)	0.417
IV	4.84	3.65	1.33 (0.98–1.80)	0.071	1.31 (0.97–1.78)	0.079
By facility type				0.165		0.188
Rural	3.23	3.27	1.01 (0.77–1.33)	0.915	1.00 (0.76–1.31)	0.988
Urban nonteaching	4.19	4.15	1.01 (0.83–1.23)	0.907	1.01 (0.83–1.23)	0.905
Urban teaching	5.66	4.59	1.23 (1.08–1.40)	0.002	1.22 (1.07–1.39)	0.003

Cost

Table 4 presents the unadjusted and adjusted cost by ILD status. After adjusting for age, sex, race/ethnicity, income quartile, and facility type, SSc-ILD was associated with 33% greater adjusted cost compared to isolated SSc (aOR: 1.33, 95% CI: 1.26 to 1.40, p < 0.001; Table 4). Age moderated the effect of ILD on cost (interaction p < 0.001); as age increased the difference in cost between patients with and without ILD decreased (Fig. 3). Biological sex moderated the effect of ILD on cost (interaction p = 0.002). Compared to isolated SSc, SSc- ILD was associated with greater adjusted cost in males relative to females; in females, SSc-ILD was associated with 28% greater adjusted cost and in males SSc-ILD was associated with 54% greater adjusted cost compared to isolated SSc (Female- aOR: 1.28, 95% CI: 1.18 to 1.38, p < 0.001; Male- aOR: 1.54, 95% CI: 1.38 to 1.72, p < 0.001, Table 4). Facility type moderated the effect of ILD on cost (interaction p = 0.008). Compared to isolated SSc, SSc-ILD was associated with greater adjusted cost in rural, urban nonteaching, and urban teaching facilities; in rural facilities SSc-ILD was associated with 23% greater adjusted cost, in urban nonteaching facilities SSc-ILD was associated with 18% greater adjusted cost, and in urban teaching facilities SSc-ILD was associated with 39% greater adjusted cost compared to isolated SSc (Rural- aOR: 1.23, 95% CI: 1.06 to 1.42, p = 0.006; Urban nonteaching- aOR: 1.18, 95% CI: 1.10–1.28, p < 0.001; Urban teaching- aOR: 1.39, 95% CI: 1.30 to 1.49, p < 0.001). Race/ethnicity and income quartile did not moderate the effect of ILD on cost (interaction p = 0.599 and p = 0.273, respectively). Main effects are provided in Table 4.

Table 4

Hospital cost by concomitant interstitial lung disease and demographic factors
	Unadjusted				Adjusted
	ILD: Yes	ILD: No	Ratio (95% CI)	p	Ratio (95% CI)	p
Cost, $	14,625	10,744	1.36 (1.29–1.44)	< 0.001	1.33 (1.26–1.40)	< 0.001
By age	Varied, see Supplemental Fig. 3			< 0.001	Varied, see Fig. 3	< 0.001
By biological sex				0.006		0.002
Female	13,967	10,672	1.31 (1.23–1.39)	< 0.001	1.28 (1.18–1.38)	< 0.001
Male	17,145	11,052	1.55 (1.39–1.74)	< 0.001	1.54 (1.38–1.72)	< 0.001
By race				0.598		0.599
White	14,128	10,159	1.39 (1.29–1.50)	< 0.001	1.36 (1.27–1.47)	< 0.001
Black	14,785	11,422	1.29 (1.17–1.43)	< 0.001	1.26 (1.15–1.39)	< 0.001
Hispanic	15,824	11,618	1.36 (1.23–1.51)	< 0.001	1.33 (1.20–1.48)	< 0.001
Other	16,304	12,782	1.28 (1.08–1.51)	0.005	1.27 (1.08–1.50)	0.004
Income quartile				0.469		0.273
I	13,845	10,274	1.35 (1.22–1.49)	< 0.001	1.28 (1.16–1.41)	< 0.001
II	13,118	10,213	1.28 (1.18–1.40)	< 0.001	1.26 (1.16–1.37)	< 0.001
III	15,269	11,141	1.37 (1.24–1.52)	< 0.001	1.35 (1.23–1.60)	< 0.001
IV	16,251	11,360	1.43 (1.29–1.59)	< 0.001	1.42 (1.28–1.58)	< 0.001
By facility type				0.009		0.008
Rural	9,066	7,222	1.26 (1.09–1.45)	0.001	1.23 (1.06–1.42)	0.006
Urban nonteaching	10,799	9,080	1.19 (1.10–1.28)	< 0.001	1.18 (1.10–1.28)	< 0.001
Urban teaching	16,584	11,864	1.40 (1.30–1.50)	< 0.001	1.39 (1.30–1.49)	< 0.001

In this retrospective, nationally (US) representative analysis, SSc-ILD was associated with 88% greater adjusted odds of inpatient mortality compared to isolated ILD (aOR 95% CI: 1.53 to 2.31). The unadjusted inpatient mortality rate for SSc-ILD was 12.11% compared to 6.38% for isolated SSc. Notably, this increase in mortality was experienced by patieints in all income quartiles. These findings underscore the significant, widespread impact of ILD on mortality outcomes across diverse socioeconomic backgrounds. In females, SSc-ILD was associated with 2.05 times greater adjusted odds of inpatient mortality compared to isolated ILD (aOR 95% C1: 1.62 to 2.50). ILD was associated with increased adjusted odds of inpatient mortality in hospitalizations of White and Hispanic patients highlighting a differential impact of SSc-ILD on mortality (p < 0.001, p = 0.011, respectively). The demographic-specific associations between ILD and inpatient mortalitiy suggest potential areas of targeted interventions and healthcare policies.

Previous studies have explored the relationship between SSc and ILD without distinguishing between inpatient and outpatient data and there is limited research on between-ILD differences in inpatient hospitalization outcomes: including mortality, LOS, and cost. In addition, most work on SSc-ILD focused on single-centers whereas our study used data from a national database (i.e., NIS). A Brazilian observational study of 380 patients with SSc demonstrated a significant increase in overall mortality for patients with SSc-ILD (p < 0.001)⁶: of the 72 patients that died, 57 had SSc-ILD. Similarly, a Norwegian study in 2019 documented an overall mortality rate of 39% for SSc patients with lung fibrosis and a 19% overall mortality for SSc patients without lung fibrosis⁷. These findings are consistent with our study which found an inpatient mortality rate of 12.1% hospitalized patients with SSc-ILD compared to a 6.4% for isolated SSc (p < 0.001). In contrary, a single center study from the University of Pennsylvania Hospital following a retrospective cohort of SSc patients from 2001–2011 found that the presence of ILD in patients with SSc was not significantly associated with higher inpatient mortality⁸. While this contradicts the findings we present, as previously mentioned, our study is based on a national level with data from hospitals across the United States.

In terms of LOS, SSc-ILD was associated with 15% longer adusted stays compared to isolated ILD (aOR 95% CI: 1.04 to 1.28). The prolonged LOS associated with SSc-ILD emphasizes the complexity of managing these patients and the need for comprehensive care strategies to address their healthcare needs. This increased LOS in SSc-ILD hospitalizations remained significant in males, females and Black, White, and Hispanic populations. Additionally, LOS was increased in all income quartiles, however the increase was statistically signifant in income quartiles I and II. These findings suggest that the financial impact of SSc-ILD (e.g., the cost associated with staying in the hospital longer) may be felt more acutely by patients in lower income brackets thereby highlighting disparities in financial burden.

Similar to our findings, a 2002–2003 NIS study found that SSc-ILD was associated with increased odds of inpatient mortality and LOS; specifically, SSc-ILD was associated with 2.63x greater odds of inpatient morality and 7.25% longer stays compared to isolated SSc⁹. In contrast to this, a 2020 study out of England documented a median LOS of less than one day consistent across all clinical groups¹⁰. Our study demonstrated SSc-ILD was associated with 15% increased adjusted LOS compared to isolated SSc hospitalizations (aOR 95% CI: 1.04 to 1.28).

Relatedly, we showed a nearly $4,000 increase in hospital associated costs for SSc-ILD hospitalizations versus isolated SSc (p < 0.001). SSc-ILD was associated with a greater costs compared to isolated ILD for all ages, genders, races, income quartiles, and hospital facility types (rural and urban). These cost differentials underscore the substantial economic burden imposed by SSc-ILD on both patients and the healthcare system, necessitating cost-effective interventions and healthcare resource allocation strategies to mitigate financial strain.

Inpatient visits are associated with a large portion of hospital costs in the US; across all diagnoses and illnesses, the average adjusted cost per inpatient stay at a community hospital was an estimated $14,101. Relatedly, 5.2% of people under 65 years had at least one hospital stay in the US in 2018¹⁶. In regards to SSc and ILD, a 2018 US study found that 53% of patients with SSc-ILD had at least 1 inpatient admission over a 5 year period while only 43% of isolated SSc patients had an inpatient admission over that same time period¹². The same study demonstrated increased healthcare costs for patients with SSc-ILD, with most of the cost attributed to inpatient visits. Similarly, a 2020 study in Australia found that SSc-ILD patients used healthcare services averaging to about $48,368 AUD per patient vs $33,657 AUD isolated ILD¹¹. These findings all align closely with the results presented in our study.

SSc-ILD has a significant prevalence and impact on patients and the healthcare system. Our study demonstrated statistical differences between isolated SSc and SSc-ILD on inpatient mortality, LOS, and hospital cost. Despite our significant findings, there were limitations. Some limitations relating to the use of the NIS database include that the database provides information only on the inpatient level with no post-hospitalization information. The NIS also provides limited information on clinical characteristics and relies on administrative billing codes to identify diagnoses and procedures. This reliance on administrative billing codes makes it difficult to distinguish between complications and comorbidities in any given patient population.

Our study highlights the major impact of SSc-ILD by demonstrating significantly higher inpatient mortality rates, increased length of hospital stays, and higher costs compared to hospitalizations of patients with isolated SSc. This was present across various demographics of age, biological sex, race/ethnicity, income quartiles, and hospital facility types. Our findings, drawn from the National Inpatient Sample (NIS) database reinforce and expand upon previous research by providing a broad and national represented perspective on the implications of SSc-ILD. The increased mortality and hospital strain associated with SSc-ILD underscores the need for heightened awareness, early diagnosis, and improved treatments for managing this complex condition. Future studies should aim to build on these findings, exploring the mechanisms behind these disparities and identifying specific strategies to improve outcomes for SSc-ILD patients.

ILD

Interstitial lung disease

SSc

Systemic sclerosis

LOS

Length of stay

NIS

National inpatient sample

HCUP

Healthcare Cost and Utilization Project

AHRQ

The Agency for Healthcare Research and Quality

ICD

International Classification of Disease

Ethics approval and consent to participate: Creighton University's Institutional Review Board acknowledged this study as Not Human Subjects Research (InfoEd record number: 2004587).

Consent for publication: Not applicable

Availability of data and materials: The National Inpatinet Sample (NIS) is publically available through the Healthcare Cost and Utlization Project (HCUP).

Competing interests: No competing interest to report

Funding: Not applicable

Authors' contributions:

Julia Jobanputra – Innovation of the idea, manuscript drafting

Nikhil Furtado – Innovation of the idea, manuscript drafting

Ali Bin Abdul Jabbar – Manuscript drafting, proofreading the paper, finalizing the conclusion.

Noureen Asghar – Study Design, innovation of the idea

Mohsin Mirza – Literature review and helping with paper reviewing.

Joseph Nahas – Literature reviewed for selection of articles for manuscript and final revision

Danielle Dilsaver – Data collection, statistical analysis, drafting of methods and results, creating of tables and figures, manuscript review

Abubakar Tauseef – Innovation of the topic, study design, literature review and final interpretation with implementation

Acknowledgments: Not applicable

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No competing interests reported.

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Influence of Interstitial Lung Disease on Systemic Sclerosis Hospitalizations, A National Study (2002-2020)

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Abstract

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Background

Methods

Data source

Aim

Cohort Identification

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Statistical Analysis

Results

Cohort Descriptives

In-patient mortality

Length of Stay

Cost

Discussion

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