Sarcoidosis diagnosis and treatment in Sweden: A register-based assessment of variations by region and calendar period

Identifying sarcoidosis trends using web search and real-world data in Sweden: a retrospective longitudinal study

Web search data are associated with disease incidence, population interest, and seasonal variations. This study aimed to investigate seasonal and geographical variations of web search data for sarcoidosis and to explore its association with external factors and sarcoidosis incidence in Sweden. Therefore, sarcoidosis-related data from Google Ads Keyword Planer (2017-2020) were generated for Sweden according to its 21 counties. The relationship between search volume and season, region, population demographics, environmental factors, and the sarcoidosis incidence listed in the National Patient Register was assessed. Analyses revealed seasonal variations for Sweden with an overall peak in the spring and autumn. Geographical differences were observed, with a higher search volume for north-western counties and the lowest search volume for Stockholm County. At the country level, the search volume was positively associated with the sarcoidosis incidence. Higher male proportion and older mean age were associated with a higher search volume, while a higher proportion of foreign-born residents, humidity, and mean temperature were associated with a lower search volume. Our analyses detected correlations between web search data, sarcoidosis incidence, and external factors. Analyses of sarcoidosis web search data therefore appear to be a valuable approach to disease surveillance to address medical needs and public interest.

History and Familial Aggregation of Immune-Mediated Diseases in Sarcoidosis: A Register-Based Case-Control-Family Study

BACKGROUND

An autoimmune component in the cause of sarcoidosis has long been debated, but population-based data on the clustering of immune-mediated diseases (IMDs) and sarcoidosis in individuals and families suggestive of shared cause are limited.

RESEARCH QUESTION

Do patients with a history of IMDs have a higher risk of sarcoidosis and do IMDs cluster in families with sarcoidosis?

STUDY DESIGN AND METHODS

We conducted a case-control-family study (2001-2020). Patients with sarcoidosis (N = 14,146) were identified in the Swedish National Patient Register using a previously validated definition (≥ 2 International Classification of Diseases [ICD]-coded inpatient or outpatient visits). At diagnosis, patients were matched to up to 10 control participants from the general population (N = 118,478) for birth year, sex, and residential location. Patients, control participants, and their first-degree relatives (FDRs; Multi-Generation Register) were ascertained for IMDs by means of ICD codes in the Patient Register (1968-2020). Conditional logistic regression was used to estimate ORs and 95% CIs of sarcoidosis associated with a history of IMDs in patients and control participants and in FDRs.

RESULTS

Patients with sarcoidosis exhibited a higher prevalence of IMDs compared with control participants (7.7% vs 4.7%), especially connective tissue diseases, cytopenia, and celiac disease. Familial aggregation was observed across IMDs; the strongest association was with celiac disease (OR, 2.09; 95% CI, 1.22-3.58), followed by cytopenia (OR, 1.88; 95% CI, 0.97-3.65), thyroiditis (OR, 1.72; 95% CI, 1.14-2.60), skin psoriasis (OR, 1.70; 95% CI, 1.34-2.15), inflammatory bowel disease (OR, 1.53; 95% CI, 1.14-2.03), immune-mediated arthritis (OR, 1.49; 95% CI, 1.20-1.85), and connective tissue disease (OR, 1.39; 95% CI, 1.00-1.93).

INTERPRETATION

This study showed that IMDs confer a higher risk of sarcoidosis and they aggregate in families with sarcoidosis, signaling a shared cause between IMDs and sarcoidosis. Our findings warrant further evaluation of shared genetic mechanisms.

Organ involvement in newly diagnosed sarcoidosis patients in the Netherlands: The first large European multicentre prospective study

BACKGROUND

Clinical presentation and prevalence of organ involvement is highly variable in sarcoidosis and depends on ethnic, genetic and geographical factors. These data are not extensively studied in a Dutch population.

AIM

To determine the prevalence of organ involvement and the indication for systemic immunosuppressive therapy in newly diagnosed sarcoidosis patients in the Netherlands.

METHODS

Two large Dutch teaching hospitals participated in this prospective cohort study. All adult patients with newly diagnosed sarcoidosis were prospectively included and a standardized work-up was performed. Organ involvement was defined using the WASOG instrument.

RESULTS

Between 2015 and 2020, a total of 330 patients were included, 55% were male, mean age was 46 (SD 14) years. Most of them were white (76%). Pulmonary involvement including thoracic lymph node enlargement was present in 316 patients (96%). Pulmonary parenchymal disease was present in 156 patients (47%). Ten patients (3%) had radiological signs of pulmonary fibrosis. Cutaneous sarcoidosis was present in 74 patients (23%). Routine ophthalmological screening revealed uveitis in 29 patients (12%, n = 256)). Cardiac and neurosarcoidosis were diagnosed in respectively five (2%) and six patients (2%). Renal involvement was observed in 11 (3%) patients. Hypercalcaemia and hypercalciuria were observed in 29 (10%) and 48 (26%, n = 182) patients, respectively. Hepatic involvement was found in 6 patients (2%). In 30% of the patients, systemic immunosuppressive treatment was started at diagnosis.

CONCLUSIONS

High-risk organ involvement in sarcoidosis is uncommon at diagnosis. Indication for systemic immunosuppressive therapy was present in a minority of patients.

Sarcoidosis in first- and second-generation immigrants: a cohort study of all adults 18 years of age and older in Sweden

BACKGROUND

There is a lack of studies on sarcoidosis among immigrants, which is of interest as there may be genetic and environmental characteristics affecting immigrants from certain countries. We aimed to study hazard ratios (HRs) of sarcoidosis in first- and second-generation immigrants, comparing them with native Swedes in the total adult Swedish population.

METHODS

We conducted a nationwide study of individuals ≥18 y of age. Sarcoidosis was defined as at least two registered diagnoses in the National Patient Register between 1 January 1998 and 31 December 2018. Cox regression analysis was used to estimate HRs with 99% confidence intervals (CIs) of first registration of sarcoidosis in first- and second-generation immigrants compared with native Swedes. The Cox regression models were stratified by sex and adjusted for age, comorbidities and sociodemographic characteristics.

RESULTS

In total, 6 175 251 were included in the first-generation study, with 12 617 cases of sarcoidosis, and 4 585 529 in the second-generation study, with 12 126 cases. The overall sarcoidosis risk was lower in foreign-born men (fully adjusted HR 0.63 [99% CI 0.57 to 0.69]) but not in foreign-born women (fully adjusted HR 0.98 [99% CI 0.90 to 1.06]). The overall risk was slightly lower in second-generation immigrants (HR 0.82 [99% CI 0.78 to 0.88]). Women from Asia exhibited a higher risk (HR 1.25 [99% CI 1.02 to 1.53)], while a potential trend was observed among women from Africa (HR 1.47 [99% CI 0.99 to 2.19]).

CONCLUSIONS

Sarcoidosis risk was lower in foreign-born men but not in women and also lower in second-generation immigrants.

Diagnostic delay of sarcoidosis: Protocol for an integrated systematic review

INTRODUCTION

Sarcoidosis is a rare systemic inflammatory granulomatous disease of unknown cause. It can manifest in any organ. The incidence of sarcoidosis varies across countries, and by ethnicity and gender. Delays in the diagnosis of sarcoidosis can lead to extension of the disease and organ impairment. Diagnosis delay is attributed in part to the lack of a single diagnostic test or unified commonly used diagnostic criteria, and to the diversity of disease manifestations and symptom load. There is a paucity of evidence examining the determinants of diagnostic delay in sarcoidosis and the experiences of people with sarcoidosis related to delayed diagnosis. We aim to systematically review available evidence about diagnostic delay in sarcoidosis to elucidate the factors associated with diagnostic delay for this disease in different contexts and settings, and the consequences for people with sarcoidosis.

METHODS AND ANALYSIS

A systematic search of the literature will be conducted using PubMed/Medline, Scopus, and ProQuest databases, and sources of grey literature, up to 25th of May 2022, with no limitations on publication date. We will include all study types (qualitative, quantitative, and mixed methods) except review articles, examining diagnostic delay, incorrect diagnosis, missed diagnosis or slow diagnosis of all types of sarcoidosis across all age groups. We will also examine evidence of patients' experiences associated with diagnostic delay. Only studies in English, German and Indonesian will be included. The outcomes we examine will be diagnostic delay time, patients' experiences, and factors associated with diagnostic delay in sarcoidosis. Two people will independently screen the titles and abstracts of search results, and then the remaining full-text documents against the inclusion criteria. Disagreements will be resolved with a third reviewer until consensus is reached. Selected studies will be appraised using the Mixed Methods Appraisal Tool (MMAT). A meta-analysis and subgroup analyses of quantitative data will be conducted. Meta-aggregation methods will be used to analyse qualitative data. If there is insufficient data for these analyses, a narrative synthesis will be conducted.

DISCUSSION

This review will provide systematic and integrated evidence on the diagnostic delay, associated factors, and experiences of diagnosis delay among people with all types of sarcoidosis. This knowledge may shed light on ways to improve diagnosis delays in diagnosis across different subpopulations, and with different disease presentations.

ETHICS AND DISSEMINATION

Ethical approval will not be required as no human recruitment or participation will be involved. Findings of the study will be disseminated through publications in peer-reviewed journals, conferences, and symposia.

TRIAL REGISTRATION

PROSPERO Registration number: CRD42022307236. URL of the PROSPERO registration: https://www.crd.york.ac.uk/PROSPEROFILES/307236_PROTOCOL_20220127.pdf.

Heterogeneity of Lung Function Phenotypes in Sarcoidosis: Role of Race and Sex Differences

Rationale: Historically, sarcoidosis was described as a restrictive lung disease, but several alternative phenotypes of pulmonary function have been observed. Pulmonary function phenotypes in sarcoidosis may represent different clinical and/or molecular phenotypes. Objectives: To characterize the prevalence of different pulmonary function phenotypes in a large and diverse sarcoidosis cohort from a tertiary care referral center. Methods: We identified individuals seen between 2005-2015 with a confirmed diagnosis of sarcoidosis. Data were collected from the first pulmonary function test (PFT) performed at our institution which included spirometry and diffusing capacity of the lung for carbon monoxide (DlCO). Demographics and clinical data were collected. Chi-squared analyses and multiple linear regressions were done to assess statistical differences and associations. Global Lung Function Initiative equations were used to calculate percent predicted measurements for spirometry and DlCO. Results: Of 602 individuals with sarcoidosis, 93% (562) had pulmonary involvement, 64% (385) were female, and 57% (341) were Black. Of those with pulmonary involvement, 56% had abnormal pulmonary function. Lung function impairment phenotypes included: 47% restriction, 22% obstruction, 15% isolated reduction in DlCO, and 16% combined obstructive restrictive phenotype. Restriction was the most common PFT phenotype among Black individuals (41%), while no lung impairment was most common among White individuals (66%) (P < 0.001). Males more frequently had obstruction (19%) compared with females (9%) P = 0.001, and females had more restriction (30%) compared with males (21%) P = 0.031. Conclusions: Among individuals with sarcoidosis and pulmonary function impairment, less than half demonstrated a restrictive phenotype. There were significant differences in pulmonary function phenotypes by race and sex.

Sarcoidosis-related mortality and the impact of corticosteroid treatment: A population-based cohort study

BACKGROUND AND OBJECTIVE

The aims of this national cohort study were: (1) to evaluate mortality in patients with sarcoidosis, stratified by gender, age and systemic corticosteroid (SC) treatment and (2) to characterize comorbidities in this cohort.

METHODS

Patients diagnosed with sarcoidosis from 2001 to 2015 were identified in the Danish National Patient Registry. Subgroup analyses were performed on cases treated/not treated with SCs within 3 years of the initial sarcoidosis diagnosis (as a proxy for disease severity). The Deyo-Charlson Comorbidity Index was used to evaluate pre-diagnostic comorbidity. Cases were matched (1:4) with controls from the general population.

RESULTS

We identified 9795 cases with sarcoidosis. Mean age was 46.5 ± 15.9 years and 55% were male. The adjusted hazard ratio (HR) for death was 1.48 (95% CI 1.31-1.68). Mortality was higher than for controls in all age groups and in both genders. HR for death for cases treated with SCs was 1.78 (95% CI 1.49-2.13) and, for cases receiving no treatment, 1.24 (95% CI 1.04-1.48). Sarcoidosis was the most commonly registered cause of death (13.3%).

CONCLUSION

Patients with sarcoidosis have an increased mortality compared with matched controls. Mortality is particularly high in patients treated with SCs.

Risk of acute myocardial infarction in sarcoidosis: A population-based cohort study from Sweden

Due to conflicting findings in previous studies, it remains unclear whether individuals with sarcoidosis are at a higher relative risk of acute myocardial infarction. In this cohort study, individuals with sarcoidosis and matched general population comparators were followed for acute myocardial infarction in Swedish nationwide registers. A small (20%) risk increase associated with sarcoidosis was identified, which did not markedly vary by age at diagnosis, sex, treatment status around diagnosis, and time since diagnosis. The highest relative risk (1.4) was observed in individuals who received immunosuppressant treatment around the time of sarcoidosis diagnosis. Future studies should examine the clinical characteristics of acute myocardial infarction in these patients and investigate whether early diagnostic or preventive interventions might be beneficial for these patients.

Comparative Effectiveness of Methotrexate versus Methylprednisolone in Treatment Naïve Pulmonary Sarcoidosis Patients

Among those who study granulomatous diseases, sarcoidosis is of tremendous interest, not only because its cause is unknown, but also because it is still as much an enigma today as it was 150 years ago when Jonathan Hutchinson first described the cutaneous form of the disease as “livid papillary psoriasis”. This piece editorializes a comparative effectiveness study of methotrexate versus methylprednisolone in treatment naïve pulmonary sarcoidosis patients for CT-guided clinical responses and drug-related adverse events.

Sarcoidosis: A nationwide registry-based study of incidence, prevalence and diagnostic work-up

INTRODUCTION

The primary objective was to evaluate the prevalence and incidence of sarcoidosis, and secondly, to evaluate differences in incidence by age at diagnosis, gender, region, calendar year and treatment and to evaluate sarcoidosis-related diagnostic work-up.

METHODS

Patients diagnosed with sarcoidosis from 2001 to 2015 and information on diagnostic procedures three months before and after initial diagnosis were identified in the Danish National Patient Register. Incidence proportion and prevalence proportion were calculated using the total population count of Danish citizens.

RESULTS

We identified 8545 sarcoidosis cases. Mean age was 46.0 ± 15.0 years, male gender was overrepresented (56.2%) and systemic corticosteroid was initiated in 46% of cases. The prevalence was 77 per 100,000 citizens in 2015. From 2001 to 2015, the incidence varied from 11.3 to 14.8 per 100,000 per year. The age-associated incidence peaked at 30-39 years in both men (23.6 per 100,000 per year) and women (15.0 per 100,000 per year). Incidence varied from 10.4 to 15.7 per 100,000 per year among regions. In particular, the share of bronchoscopies and chest-computed tomography were high in the region with the highest incidence and low in the region with the lowest incidence. Invasive procedures were more frequently performed in patients treated with systemic corticosteroid.

CONCLUSION

We find an increasing incidence and prevalence of sarcoidosis, with a peak incidence for both men and women between 30 and 39 years of age. The share of procedures performed seems to correlate well with incidence and disease severity.

Sarcoidosis epidemiology: recent estimates of incidence, prevalence and risk factors

PURPOSE OF REVIEW

The aim of this review is to describe the latest studies on sarcoidosis incidence, prevalence and risk factors with a special focus on reports in the last 2 years. The potential biases affecting these studies are discussed.

RECENT FINDINGS

The prevalence and incidence of sarcoidosis vary greatly depending on region of the world. Variations in data sources and settings can affect estimates of the burden of sarcoidosis, sometimes making them difficult to compare across countries. It is not well understood how the distribution of sarcoidosis phenotypes differs across populations. Age, sex and race are the most important sources of variation in incidence and prevalence. Recent epidemiological studies provide new insights on the role of genetic and nongenetic risk factors for sarcoidosis.

SUMMARY

High-quality and systematically collected data, with depth (detailed information per individual) and breadth (many individuals), is needed to further understand the complexity and heterogeneity of sarcoidosis.

Type 2 diabetes risk in sarcoidosis patients untreated and treated with corticosteroids

Background

The rate of type 2 diabetes mellitus (T2D) is increased in sarcoidosis patients but it is unknown if corticosteroid treatment plays a role. We investigated whether the T2D risk is higher in untreated and corticosteroid-treated sarcoidosis patients compared with the general population.

Methods

In this cohort study, individuals with two or more International Statistical Classification of Diseases and Related Health Problems (ICD) codes for sarcoidosis were identified from the Swedish National Patient Register (NPR) (n=5754). Corticosteroid dispensations within 3 months before or after the first sarcoidosis diagnosis were identified from the Swedish Prescribed Drug Register (PDR). General population comparators without sarcoidosis were matched to cases 10:1 on age, sex and region of residence (n=61 297). Incident T2D was identified using ICD codes (NPR) and antidiabetic drug dispensations (PDR). Follow-up was from the second sarcoidosis diagnosis/matching date until T2D, emigration, death or study end (December 2013). Cox regression models adjusted for age, sex, education, country of birth, healthcare regions and family history of diabetes were used to estimate hazard ratios (HRs). We used flexible parametric models to examine the T2D risk over time.

Results

40% of sarcoidosis patients were treated with corticosteroid at diagnosis. The T2D rate was 7.7 per 1000 person-years in untreated sarcoidosis, 12.7 per 1000 person-years in corticosteroid-treated sarcoidosis and 5.5 per 1000 person-years in comparators. The HR for T2D was 1.4 (95% CI 1.2-1.8) associated with untreated sarcoidosis and 2.3 (95% CI 2.0-3.0) associated with corticosteroid-treated sarcoidosis. The T2D risk was highest for corticosteroid-treated sarcoidosis in the first 2 years after diagnosis.

Conclusions

Sarcoidosis is associated with an increased risk of T2D especially in older, male, corticosteroid-treated patients at diagnosis. Screening for T2D for these patients is advisable.

Risk and predictors of heart failure in sarcoidosis in a population-based cohort study from Sweden

OBJECTIVES

Previous studies showed a strong association between sarcoidosis and heart failure (HF) but did not consider risk stratification or risk factors to identify useful aetiological insights. We estimated overall and stratified HRs and identified risk factors for HF in sarcoidosis.

METHODS

Sarcoidosis cases were identified from the Swedish National Patient Register (NPR; ≥2 International Classification of Diseases-coded visits, 2003-2013) and matched to general population comparators. They were followed for HF in the NPR. Treated were cases who were dispensed ≥1 immunosuppressant ±3 months from the first sarcoidosis visit (2006-2013). Using Cox models, we estimated HRs adjusted for demographics and comorbidity and identified independent risk factors of HF together with their attributable fractions (AFs).

RESULTS

During follow-up, 204 of 8574 sarcoidosis cases and 721 of 84 192 comparators were diagnosed with HF (rate 2.2 vs 0.7/1000 person-years, respectively). The HR associated with sarcoidosis was 2.43 (95% CI 2.06 to 2.86) and did not vary by age, sex or treatment status. It was higher during the first 2 years after diagnosis (HR 3.7 vs 1.9) and in individuals without a history of ischaemic heart disease (IHD; HR 2.7 vs 1.7). Diabetes, atrial fibrillation and other arrhythmias were the strongest independent clinical predictors of HF (HR 2.5 each, 2-year AF 20%, 16% and 12%, respectively).

CONCLUSIONS

Although low, the HF rate was more than twofold increased in sarcoidosis compared with the general population, particularly right after diagnosis. IHD history cannot solely explain these risks, whereas ventricular arrhythmias indicating cardiac sarcoidosis appear to be a strong predictor of HF in sarcoidosis.

Infection risk in sarcoidosis patients treated with methotrexate compared to azathioprine: A retrospective 'target trial' emulated with Swedish real-world data

The 6‐month infection risk was 43% lower in patients with sarcoidosis who initiated methotrexate compared to those who started azathioprine. Our findings suggest that unless contraindications exist, methotrexate should be preferred over azathioprine as the primary steroid‐sparing choice in individuals with sarcoidosis.

Background and objective

No clinical trial has examined the risk of infection associated methotrexate and azathioprine, two advocated treatments for sarcoidosis. We aimed to compare the 6‐month risk of infection after the initiation of methotrexate or azathioprine.

Methods

We conducted a retrospective target trial emulation using Swedish pre‐existing data. We searched for eligible participants who were dispensed methotrexate or azathioprine in the Prescribed Drug Register (PDR) every day between January 2007 and June 2013. Adults were eligible if they had ≥2 ICD‐coded visits for sarcoidosis in the National Patient Register (NPR) and were dispensed ≥1 systemic corticosteroid but no methotrexate or azathioprine in the past 6 months (PDR). Within 6 months of methotrexate or azathioprine initiation, diagnosis of infectious disease was identified (visit in the NPR where infectious disease was the primary diagnosis). We estimated RR and risk differences comparing methotrexate (n = 667) to azathioprine initiations (n = 259) using targeted maximum likelihood estimation (TMLE) adjusting for demographic factors, comorbidity and sarcoidosis severity proxies.

Results

There were 43 infections in the methotrexate group (adjusted 6‐month risk 6.8%) and 29 infections in the azathioprine group (12.0%). The RR for infectious disease at 6 months associated with methotrexate compared to azathioprine initiation was 0.57 (95% CI: 0.39, 0.82) and the risk difference was −5.2% (95% CI: −8.5%, −1.8%). The RR at 9 months was attenuated to 0.77 (95% CI: 0.52, 1.14).

Conclusion

Methotrexate appears to be associated with a lower risk of infection in sarcoidosis than azathioprine, but randomized trials should confirm this finding.

Risk of first and recurrent serious infection in sarcoidosis: a Swedish register-based cohort study

Serious infections impair quality of life and increase costs. Our aim was to determine if sarcoidosis is associated with a higher rate of serious infection and whether this varies by age, sex, time since diagnosis or treatment status around diagnosis.

We compared individuals with sarcoidosis (at least two International Classification of Diseases codes in the Swedish National Patient Register 2003–2013; n=8737) and general population comparators matched 10:1 on age, sex and residential location (n=86 376). Patients diagnosed in 2006–2013 who were dispensed at least one immunosuppressant ±3 months from diagnosis (Swedish Prescribed Drug Register) were identified. Cases and comparators were followed in the National Patient Register for hospitalisations for infection. Using Cox and flexible parametric models, we estimated adjusted hazard ratios (aHR) and 95% confidence intervals for first and recurrent serious infections (new serious infection >30 days after previous).

We identified 895 first serious infections in sarcoidosis patients and 3881 in comparators. The rate of serious infection was increased 1.8-fold in sarcoidosis compared to the general population (aHR 1.81, 95% CI 1.65–1.98). The aHR was higher in females than males and during the first 2 years of follow-up. Sarcoidosis cases treated with immunosuppressants around diagnosis had a three-fold increased risk, whereas nontreated patients had a 50% increased risk. The rate of serious infection recurrence was 2.8-fold higher in cases than in comparators.

Serious infections are more common in sarcoidosis than in the general population, particularly during the first few years after diagnosis. Patients who need immunosuppressant treatment around diagnosis are twice as likely to develop a serious infection than those who do not.

Sarcoidosis is associated with an increased risk of serious infections, especially during the first 2 years after diagnosis. Patients in need of immunosuppressants around diagnosis are twice as likely to develop serious infections than those who do not.https://bit.ly/2VFOvSo

Are infectious diseases risk factors for sarcoidosis or a result of reverse causation? Findings from a population-based nested case-control study

Findings from molecular studies suggesting that several infectious agents cause sarcoidosis are intriguing yet conflicting and likely biased due to their cross-sectional design. As done in other inflammatory diseases to overcome this issue, prospectively-collected register data could be used, but reverse causation is a threat when the onset of disease is difficult to establish. We investigated the association between infectious diseases and sarcoidosis to understand if they are etiologically related. We conducted a nested case-control study (2009-2013) using incident sarcoidosis cases from the Swedish National Patient Register (n = 4075) and matched general population controls (n = 40,688). Infectious disease was defined using inpatient/outpatient visits and/or antimicrobial dispensations starting 3 years before diagnosis/matching. Adjusted odds ratios (aOR) of sarcoidosis were estimated using conditional logistic regression and tested for robustness assuming the presence of reverse causation bias. The aOR of sarcoidosis associated with history of infectious disease was 1.19 (95% confidence interval [CI] 1.09, 1.29; 21% vs. 16% exposed cases and controls, respectively). Upper respiratory and ocular infections conferred the highest OR. Findings were similar when we altered the infection definition or varied the infection-sarcoidosis latency period (1-7 years). In bias analyses assuming one in 10 infections occurred because of preclinical sarcoidosis, the observed association was completely attenuated (aOR 1.02; 95% CI 0.90, 1.15). Our findings, likely induced by reverse causation due to preclinical sarcoidosis, do not support the hypothesis that common symptomatic infectious diseases are etiologically linked to sarcoidosis. Caution for reverse causation bias is required when the real disease onset is unknown.