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A valid study design is essential when assessing the safety of drugs based on observational data. The comparator group is a key element of the design and can greatly influence the results. The active comparator new user design is a go-to design in observational drug safety research where a target trial of initiation of a study drug versus usual care is emulated. A comparison with another treatment that targets similar patients as the study drug and has no effect on the outcome has great potential to reduce bias. However, the active comparator new user design can be difficult to implement because no suitable comparator drug is available or because it requires extensive exclusion of study drug initiators. In this analysis, we evaluated alternative study designs that can be used in drug safety assessments when the active comparator new user design is not optimal. Using target trial emulation as a common framework, we defined and evaluated the following designs: traditional no use, no-use episodes, active comparator new user, prevalent new user, generalized prevalent new user, and hierarchical prevalent new user. We showed that all designs can be implemented by using sequential cohorts and simply altering the patient selection criteria, i.e., identifying increasingly restrictive cohorts. In this way, all designs are nested in each other and the differences between them can be demonstrated clearly. We concluded that many study-specific factors need to be considered when choosing a design, including indication, available comparator drugs, treatment patterns, potential effect modification, and sample size.

OBJECTIVE To assess the association between use of sodium–glucose cotransporter 2 (SGLT2) inhibitors and the risk of new-onset atrial fibrillation (AF) in routine clinical practice. RESEARCH DESIGN AND METHODS We used nationwide registers in Denmark, Norway, and Sweden from 2013 to 2018 in order to include patients without a history of AF who were newly prescribed an SGLT2 inhibitor or an active comparator (glucagon-like peptide 1 [GLP-1] receptor agonist). We performed a cohort study to assess new-onset AF in intention-to-treat analyses using Cox regression, adjusted for baseline covariates with propensity score weighting. RESULTS We identified 79,343 new users of SGLT2 inhibitors (59.2% dapagliflozin, 40.0% empagliflozin, 0.8% canagliflozin, CONCLUSIONS In this cohort study using nationwide data from three countries, use of SGLT2 inhibitors, compared with GLP-1 receptor agonists, was associated with a modestly reduced risk of new-onset AF.

ObjectiveTo evaluate the association between use of proton pump inhibitors (PPIs) and risk of pneumonia in children.DesignNationwide register-based self-controlled case series study.SettingSweden, July 2006 to December 2016.ParticipantsChildren aged Main outcomes and measuresThe primary analysis examined the risk of pneumonia during the risk period (ongoing PPI treatment), the pre-exposure period (≤30 days preceding PPI treatment) and the postexposure period (days 1–365 after PPI discontinuation), comparing to the unexposed period. Conditional Poisson regression was used to estimate incidence rate ratios (IRRs) and 95% CIs.ResultsA total of 2356 cases of pneumonia were included. Compared with the unexposed period, the risk of pneumonia was significantly increased during ongoing PPI treatment, with an adjusted IRR of 1.40 (95% CI 1.21 to 1.62). The risk of pneumonia was also increased in the pre-exposure period (adjusted IRR, 1.80, 95% CI 1.51 to 2.13), but not in the postexposure period (adjusted IRR 0.98, 95% CI 0.89 to 1.08). Dividing the risk period by time since treatment initiation, the increased risk of pneumonia was highest in the first 30 days (adjusted IRR 1.63, 95% CI 1.35 to 1.97), remained during days 31–90 (adjusted IRR 1.32, 95% CI 1.04 to 1.69), but waned in days ≥91 (IRR 1.06, 95% CI 0.79 to 1.41).Conclusions and relevanceAn increased risk of pneumonia was observed both immediately before and immediately after PPI initiation. This pattern of association can likely be explained by an underlying risk of pneumonia due to factors transiently present at the time around PPI initiation. Thus, our findings do not support a causal relationship between PPI use and risk of pneumonia.

Background and Objectives Tumor necrosis factor-alpha (TNF-α) inhibitors are efficacious and considered generally safe in adults. However, pediatric-specific safety evidence is scarce. The aim of this study was to screen for signals of previously unknown adverse events of TNF-α inhibitors in pediatric patients. Methods We conducted a data-mining study based on routinely collected, nationwide Danish healthcare data for 2004–2016. Using tree-based scan statistics to identify events with unexpectedly high incidence during TNF-α inhibitor use among patients with inflammatory bowel disease or juvenile idiopathic arthritis, two analyses were performed: comparison with episodes of no use and with other time periods from the same patient. Based on incident physician-assigned diagnosis codes from outpatient and inpatient visits in specialist care, we screened thousands of potential adverse events while adjusting for multiple testing. Results We identified 1310 episodes of new TNF-α inhibitor use that met the eligibility criteria. Two signals of adverse events of TNF-α inhibitors, as compared with no use, were detected. First, there were excess events of dermatologic complications (ICD-10: L00-L99, 87 vs. 44 events, risk difference [RD] 3.3%), which have been described previously in adults and children. Second, there were excess events of psychiatric diagnosis adjustment disorders (ICD-10: F432, 33 vs. 7 events, RD 2.0%), which was likely associated with the underlying disease and its severity, rather than with the treatment. The self-controlled analysis generated no signal. Conclusions No signals of previously unknown adverse events of TNF-α inhibitors in pediatric patients were detected. The study showed that real-world data and newly developed methods for adverse events data mining can play a particularly important role in pediatrics where pre-approval drug safety data are scarce. Electronic supplementary material The online version of this article (10.1007/s40261-020-00977-5) contains supplementary material, which is available to authorized users.

OBJECTIVE To assess the association between use of glucagon-like peptide 1 (GLP-1) receptor agonists and risk of serious renal events in routine clinical practice. RESEARCH DESIGN AND METHODS This was a cohort study using an active-comparator, new-user design and nationwide register data from Sweden, Denmark, and Norway during 2010–2016. The cohort included 38,731 new users of GLP-1 receptor agonists (liraglutide 92.5%, exenatide 6.2%, lixisenatide 0.7%, and dulaglutide 0.6%), matched 1:1 on age, sex, and propensity score to a new user of the active comparator, dipeptidyl peptidase 4 (DPP-4) inhibitors. The main outcome was serious renal events, a composite including renal replacement therapy, death from renal causes, and hospitalization for renal events. Secondary outcomes were the individual components of the main outcome. Hazard ratios (HRs) were estimated using Cox models and an intention-to-treat exposure definition. Mean (SD) follow-up time was 3.0 (1.7) years. RESULTS Mean (SD) age of the study population was 59 (10) years, and 18% had cardiovascular disease. A serious renal event occurred in 570 users of GLP-1 receptor agonists (incidence rate 4.8 events per 1,000 person-years) and in 722 users of DPP-4 inhibitors (6.3 events per 1,000 person-years, HR 0.76 [95% CI 0.68–0.85], absolute difference −1.5 events per 1,000 person-years [−2.1 to −0.9]). Use of GLP-1 receptor agonists was associated with a significantly lower risk of renal replacement therapy (HR 0.73 [0.62–0.87]) and hospitalization for renal events (HR 0.73 [0.65–0.83]) but not death from renal causes (HR 0.72 [0.48–1.10]). When we used an as-treated exposure definition in which patients were censored at treatment cessation or switch to the other study drug, the HR for the primary outcome was 0.60 (0.49–0.74). CONCLUSIONS In this large cohort of patients seen in routine clinical practice in three countries, use of GLP-1 receptor agonists, as compared with DPP-4 inhibitors, was associated with a reduced risk of serious renal events.

Aim: To assess the comparative cardiovascular and renal effectiveness of sodium-glucose co-transporter-2 (SGLT2) inhibitors versus glucagon-like peptide-1 (GLP-1) receptor agonists in routine clinical practice. Materials and Methods: A cohort study of nationwide registers from Sweden, Denmark, and Norway, including 87 525 new users of SGLT2 inhibitors and 63 921 new users of GLP-1 receptor agonists, was conducted using data from 2013-2018. Co-primary outcomes, analysed using an intention-to-treat exposure definition, were major adverse cardiovascular events (MACE; myocardial infarction, stroke, and cardiovascular death), heart failure (hospitalization or death because of heart failure), and serious renal events (renal replacement therapy, hospitalization for renal events, and death from renal causes). Results: Use of SGLT2 inhibitors versus GLP-1 receptor agonists was associated with a higher risk of MACE (adjusted incidence rate: 15.2 vs. 14.4 events per 1000 person-years; HR 1.07 [95% CI 1.01-1.15]), a similar risk of heart failure (6.0 vs. 6.0 events per 1000 person-years; HR 1.02 [0.92-1.12]), and a lower risk of serious renal events (2.9 vs. 4.0 events per 1000 person-years; HR 0.76 [0.66-0.87]). In as-treated analyses, the HR (95% CI) was 1.11 (1.00-1.24) for MACE, 0.88 (0.74-1.04) for heart failure, and 0.60 (0.47-0.77) for serious renal events. In secondary outcome analyses, use of SGLT2 inhibitors versus GLP-1 receptor agonists was not associated with statistically significant differences for the risk of myocardial infarction (HR 1.09 [95% CI 1.00-1.19]), cardiovascular death (HR 0.97 [95% CI 0.84-1.12]), death from renal causes (HR 0.75 [95% CI 0.41-1.35]), or any cause death (HR 1.01 [95% CI 0.94-1.09]), while the risk of stroke was higher (HR 1.14 [95% CI 1.03-1.26]), and the risk of renal replacement therapy (HR 0.74 [95% CI 0.56-0.97]) and hospitalization for renal events (HR 0.75 [95% CI 0.65-0.88]) were lower among users of SGLT2 inhibitors. Conclusions: Use of SGLT2 inhibitors versus GLP-1 receptor agonists was associated with a similar risk of heart failure and a lower risk of serious renal events, while use of GLP-1 receptor agonists versus SGLT2 inhibitors was associated with a slightly lower risk of MACE. In as-treated analyses, the associations with MACE and serious renal events increased in magnitude, and the HR for heart failure tended towards a protective association for SGLT2 inhibitors.

Although some data have linked proton pump inhibitor (PPI) use to risk of depression and anxiety, there are no studies investigating this safety issue in children. This study investigated the association between PPI use and risk of depression and anxiety in children. We conducted a nationwide register-based cohort study in Sweden, July 1, 2007, to December 31, 2016. Following matching on age and propensity score, we included 29,320 pairs of PPI initiators and noninitiators among children aged 7-17 years old. The primary analysis examined the risk of incident depression and anxiety, a composite outcome defined as a diagnosis of depression, anxiety, or a prescription for an antidepressant. Children who initiated PPI use had higher hazards for risk of depression and anxiety compared with noninitiators (hazard ratios [HRs], 2.61; 95% confidence interval [CI], 2.32-2.94). In analyses of the timing of depression and anxiety onset after PPI initiation, the HRs were 3.71 (95% CI, 2.17-6.34) for 1-30 days, 3.47 (95% CI, 2.33-5.18) for 31-90 days, 2.71 (2.04-3.60) for 91-180 days, 2.52 (2.00-3.16) for 181-365 days, and 2.34 (1.94-2.82) for 366-730 days. Significant associations were observed across all age groups. The magnitude of the association increased with longer duration of PPI use (p for trend0.0001). The association was consistent through all sensitivity analyses, including high-dimensional propensity score matching (HR, 2.31, 95% CI, 2.05-2.61). PPI use was associated with increased risk of depression and anxiety in children. Further investigation is warranted to confirm or refute this potential association.

Studies have shown an association between use of tumour necrosis factor-α (TNFα) inhibitors and increased risk of serious infection in adult inflammatory bowel disease (IBD). However, data on this topic for paediatric patients are scarce and inconclusive. The aim of this study was to investigate whether there is an association between the use of TNFα inhibitors and the risk of serious infection in children with IBD.In this nationwide Danish cohort study, we searched health registers (from Jan 1, 2007, to Dec 31, 2016) to identify episodes of children and adolescents (18 years) with at least two recorded IBD diagnoses in specialist care. We categorised follow-up time in mutually exclusive episodes of incident TNFα inhibitor use or no TNFα inhibitor use from specialist care records. We used Cox proportional hazards models to estimate hazard ratios (HRs), adjusting using propensity score weighting for demographic characteristics, comorbidities, treatment history, health-care use, and indicators of disease severity. The primary outcome, incident serious infection, was defined as infection requiring a stay in hospital and was identified through hospital records.Among 2817 paediatric patients with IBD, we identified 618 episodes of incident TNFα inhibitor use and 2925 episodes of no TNFα inhibitor use. In the cohort of exposed and not exposed episodes that was propensity-score weighted, 53·9% were of male sex, the mean age was 15·1 (SD 1·7) years, 69·9% had Crohn's disease, and 30·1% had ulcerative colitis or IBD-unclassified; median follow-up was 1·4 years (IQR 0·4-3·0). The weighted incidence of serious infection was 54·6 events per 1000 patient-years for the TNFα inhibitor episodes and 61·9 events per 1000 patient-years for the no-use episodes. The weighted HR of serious infection associated with TNFα inhibitor use was 0·81 (95% CI 0·54-1·21).There was no significant association between use of TNFα inhibitors and the risk of serious infection in children with IBD, and, based on the upper bound of the confidence interval, a relatively small risk increase seems unlikely, contrary to previous findings in adults. Observational data such as these can support paediatric clinical practice.Swedish Research Council, Frimurare Barnhuset Foundation, and the Åke Wiberg Foundation.

Aims/hypothesis Concerns have been raised regarding a potential association of use of the incretin-based drugs dipeptidyl peptidase 4 (DPP4) inhibitors and glucagon-like peptide-1 (GLP-1)-receptor agonists with risk of cholangiocarcinoma. We examined this association in nationwide data from three countries. Methods We used data from nationwide registers in Sweden, Denmark and Norway, 2007–2018, to conduct two cohort studies, one for DPP4 inhibitors and one for GLP-1-receptor agonists, to investigate the risk of incident cholangiocarcinoma compared with an active-comparator drug class (sulfonylureas). The cohorts included patients initiating treatment episodes with DPP4 inhibitors vs sulfonylureas, and GLP-1-receptor agonists vs sulfonylureas. We used Cox regression models, adjusted for potential confounders, to estimate hazard ratios from day 366 after treatment initiation to account for cancer latency. Results The main analyses of DPP4 inhibitors included 1,414,144 person-years of follow-up from 222,577 patients receiving DPP4 inhibitors (median [IQR] follow-up time, 4.5 [2.6–7.0] years) and 123,908 patients receiving sulfonylureas (median [IQR] follow-up time, 5.1 [2.9–7.8] years) during which 350 cholangiocarcinoma events occurred. Use of DPP4 inhibitors, compared with sulfonylureas, was not associated with a statistically significant increase in risk of cholangiocarcinoma (incidence rate 26 vs 23 per 100,000 person-years; adjusted HR, 1.15 [95% CI 0.90, 1.46]; absolute rate difference 3 [95% CI -3, 10] events per 100,000 person-years). The main analyses of GLP-1-receptor agonists included 1,036,587 person-years of follow-up from 96,813 patients receiving GLP-1-receptor agonists (median [IQR] follow-up time, 4.4 [2.4–6.9] years) and 142,578 patients receiving sulfonylureas (median [IQR] follow-up time, 5.5 [3.2–8.1] years) during which 249 cholangiocarcinoma events occurred. Use of GLP-1-receptor agonists was not associated with a statistically significant increase in risk of cholangiocarcinoma (incidence rate 26 vs 23 per 100,000 person-years; adjusted HR, 1.25 [95% CI 0.89, 1.76]; absolute rate difference 3 [95% CI -5, 13] events per 100,000 patient-years). Conclusions/interpretation In this analysis using nationwide data from three countries, use of DPP4 inhibitors and GLP-1-receptor agonists, compared with sulfonylureas, was not associated with a significantly increased risk of cholangiocarcinoma. Graphical abstract

Background Hypercoagulability and thromboembolism are prominent features of severe COVID-19, and ongoing anticoagulant use might be protective. Methods We conducted a nationwide register-based cohort study in Sweden, February through May, 2020, to assess whether ongoing direct oral anticoagulant (DOAC) use was associated with reduced risk of hospital admission for laboratory-confirmed COVID-19, or a composite of intensive care unit (ICU) admission or death due to laboratory-confirmed COVID-19. Results DOAC use (n = 103 703) was not associated with reduced risk of hospital admission for COVID-19 (adjusted hazard ratio [aHR] [95% confidence interval] 1.00 [0.75-1.33] vs. nonuse atrial fibrillation comparator [n = 36 875]; and aHR 0.94 [0.80-1.10] vs. nonuse cardiovascular disease comparator [n = 355 699]), or ICU admission or death due to COVID-19 (aHRs 0.76 [0.51-1.12], and 0.90 [0.71-1.15], respectively). Conclusion Ongoing DOAC use was not associated with reduced risk of severe COVID-19, indicating that prognosis would not be modified by early outpatient DOAC initiation.

To assess the association between use of sodium-glucose co-transporter 2 (SGLT2) inhibitors and risk of serious renal events in data from routine clinical practice.Cohort study using an active comparator, new user design and nationwide register data.Sweden, Denmark, and Norway, 2013-18.Cohort of 29 887 new users of SGLT2 inhibitors (follow-up time: dapagliflozin 66.1%; empagliflozin 32.6%; canagliflozin 1.3%) and 29 887 new users of an active comparator, dipeptidyl peptidase-4 inhibitors, matched 1:1 on the basis of a propensity score with 57 variables. Mean follow-up time was 1.7 (SD 1.0) years.SGLT2 inhibitors versus dipeptidyl peptidase-4 inhibitors, defined by filled prescriptions and analysed according to intention to treat.The main outcome was serious renal events, a composite including renal replacement therapy, death from renal causes, and hospital admission for renal events. Secondary outcomes were the individual components of the main outcome.The mean age of the study population was 61.3 (SD 10.5) years; 11 108 (19%) had cardiovascular disease, and 1974 (3%) had chronic kidney disease. Use of SGLT2 inhibitors, compared with dipeptidyl peptidase-4 inhibitors, was associated with a reduced risk of serious renal events (2.6 events per 1000 person years versus 6.2 events per 1000 person years; hazard ratio 0.42 (95% confidence interval 0.34 to 0.53); absolute difference -3.6 (-4.4 to -2.8) events per 1000 person years). In secondary outcome analyses, the hazard ratio for use of SGLT2 inhibitors versus dipeptidyl peptidase-4 inhibitors was 0.32 (0.22 to 0.47) for renal replacement therapy, 0.41 (0.32 to 0.52) for hospital admission for renal events, and 0.77 (0.26 to 2.23) for death from renal causes. In sensitivity analyses in each of the Swedish and Danish parts of the cohort, the model was further adjusted for glycated haemoglobin and estimated glomerular filtration rate (Sweden and Denmark) and for blood pressure, body mass index, and smoking (Sweden only); in these analyses, the hazard ratio moved from 0.41 (0.26 to 0.66) to 0.50 (0.31 to 0.81) in Sweden and from 0.42 (0.32 to 0.56) to 0.55 (0.41 to 0.74) in Denmark.In this analysis using nationwide data from three countries, use of SGLT2 inhibitors, compared with dipeptidyl peptidase-4 inhibitors, was associated with a significantly reduced risk of serious renal events.

Objective To assess the association between use of GLP1-receptor-agonists and risk of serious renal events in routine clinical practice. Research Design and Methods Cohort study using an active-comparator new-user design and nationwide register data from Sweden, Denmark and Norway, 2010-2016. The cohort included 38,731 new users of GLP1-receptor-agonists (liraglutide 92.5%; exenatide 6.2%; lixisenatide 0.7%; dulaglutide 0.6%), matched 1:1 on age, sex and propensity score to a new user of the active comparator, dipeptidyl-peptidase-4 (DPP-4) inhibitors. The main outcome was serious renal events, a composite including renal replacement therapy, death from renal causes and hospitalization for renal events. Secondary outcomes were the individual components of the main outcome. Hazard ratios (HRs) were estimated using Cox models and an intention-to-treat exposure definition. Mean (SD) follow-up time was 3.0 (1.7) years. Results Mean (SD) age of the study population was 59 (10) years and 18% had cardiovascular disease. A serious renal event occurred in 570 users of GLP1-receptor-agonists (incidence rate 4.8 events per 1000 person-years) and in 722 users of DPP4 inhibitors (6.3 events per 1000 person-years; hazard ratio [HR] 0.76, 95% CI 0.68-0.85; absolute difference -1.5 [-2.1 to -0.9] events per 1000 person-years). Use of GLP1-receptor-agonists was associated with a significantly lower risk of renal replacement therapy (HR 0.73 [0.62-0.87]) and hospitalization for renal events (HR 0.73 [0.65-0.83]) but not death from renal causes (HR 0.72 [0.48-1.10]). When using an as-treated exposure definition in which patients were censored at treatment cessation or switch to the other study drug, the HR for the primary outcome was 0.60 (0.49-0.74). Conclusion In this large cohort of patients seen in routine clinical practice in three countries, use of GLP1-receptor-agonists, as compared with DPP4 inhibitors, was associated with a reduced risk of serious renal events.

Importance Proton pump inhibitor (PPI) use has been linked to increased risk of fracture in adults. Despite a trend in prescription of PPIs in children, there is scarce evidence regarding this safety concern in pediatric patients. Objective To evaluate the association between PPI use and risk of fracture in children. Design This nationwide register-based cohort study included data from Sweden from July 2006 to December 2016. Children younger than 18 years who initiated PPI use were matched on propensity score and age with those who did not initiate PPI use. Exposure Initiation of PPI use. Main Outcomes and Measures Cox regression was adopted to estimate hazard ratios (HRs) for a first fracture of any type and 5 subtypes of fracture, with follow-up for up to 5 years. To address potential residual confounding, high-dimensional propensity score matching and a direct comparison with histamine-2 receptor antagonists were performed. Results There were a total of 115 933 pairs of children included. During a mean (SD) of 2.2 (1.6) years of follow-up, 5354 and 4568 cases of any fracture occurred among those who initiated PPIs vs those who did not, respectively (20.2 vs 18.3 events per 1000 person-years; hazard ratio [HR], 1.11 [95% CI, 1.06-1.15]). Use of PPIs was associated with increased risk of upper-limb fracture (HR, 1.08 [95% CI, 1.03-1.13]), lower-limb fracture (HR, 1.19 [95% CI, 1.10-1.29]), and other fractures (HR, 1.51 [95% CI, 1.16-1.97]) but not head fracture (HR, 0.93 [95% CI, 0.76-1.13]) or spine fracture (HR, 1.31 [95% CI, 0.95-1.81]). The HRs for fracture according to cumulative duration of PPI use were 1.08 (95% CI, 1.03-1.13) for 30 days or less, 1.14 (95% CI, 1.09-1.20) for 31 to 364 days, and 1.34 (95% CI, 1.13-1.58) for 365 days or more. The association was consistent in most sensitivity analyses, including high-dimensional propensity score matching (HR, 1.10 [95% CI, 1.06-1.15]), although the analysis of PPI vs histamine-2 receptor antagonist did not reach statistical significance (HR, 1.06 [95% CI, 0.97-1.15]). Conclusions and Relevance In this large pediatric cohort, PPI use was associated with a small but significant increased risk of any fracture. Risk of fracture should be taken into account when weighing the benefits and risks of PPI treatment in children.

Background: Improved understanding of the impact of kidney transplantation on healthcare resource use/costs and loss of productivity could aid decision making about funding allocation and resources needed for the treatment of chronic kidney disease in stage 5. Material/Methods: This was a retrospective study utilizing data from Swedish national health registers of patients undergoing kidney transplantation. Primary outcomes were renal disease-related healthcare resource utilization and costs during the 5 years after transplantation. Secondary outcomes included total costs and loss of productivity. Regression analysis identified factors that influenced resource use, costs, and loss of productivity. Results: During the first year after transplantation, patients (N=3120) spent a mean of 25.7 days in hospital and made 21.6 outpatient visits; mean renal disease-related total cost was & euro;66,014. During the next 4 years, resource use was approximately 70% (outpatient) to 80% (inpatient) lower, and costs were 75% lower. Before transplantation, 62.8% were on long-term sick leave, compared with 47.4% 2 years later. Higher resource use and costs were associated with age

Purpose Estimating disease incidence based on secondary data requires a look-back period to exclude patients with pre-existing disease from the incidence risk set. However, the optimal length of the look-back period and its impact on incidence rates are often unknown. We studied the impact of the length of the look-back period on incidence rates of 24 different chronic diseases. Methods Everyone residing in Sweden between January 1, 2005 and December 31, 2013 were identified from national registries and followed up to 2 years (through December 31, 2015). Outcome events were identified from inpatient and outpatient hospital contacts and incidence rates were calculated per 100 000 person-years. The length of the look-back period was varied with 6-month increments, starting at 6 months. The maximum look-back period of 9 years was used as reference period. Results There were 7 943 807 individuals with a look-back period of at least 9 years (mean age 46.5 years) and a mean follow-up time of 1.97 years. Incidence rates were higher across all diseases when restricting the look-back to 1 year compared to 9 years, with a magnitude of overestimation of the incidence rates between 13% (temporal arteritis) and 174% (type 1 diabetes). However, for most diseases the effect of extending the look-back period beyond 3-5 years appeared comparably small. Conclusions This study illustrates how short look-back periods cause overestimation of the incidence rates of chronic diseases, suggesting that sensitivity analyses with respect to look-back period are considered, particularly using data sources with limited information on past medical history.

IMPORTANCE: The use of proton pump inhibitors (PPIs) in children has increased substantially in recent years, concurrently with emerging concerns that these drugs may increase the risk of asthma. Whether PPI use in the broad pediatric population is associated with increased risk of asthma is not known. OBJECTIVE: To investigate the association between PPI use and risk of asthma in children. DESIGN, SETTING, AND PARTICIPANTS: This nationwide cohort study collected registry data in Sweden from January 1, 2007, to December 31, 2016. Children and adolescents 17 years or younger were matched by age and propensity score into 80 870 pairs of those who initiated PPI use and those who did not. Data were analyzed from February 1 to September 1, 2020. EXPOSURES: Initiation of PPI use. MAIN OUTCOMES AND MEASURES: The primary analysis examined the risk of incident asthma with a median follow-up to 3.0 (interquartile range, 2.1-3.0) years. Cox proportional hazards regression was used to estimate hazard ratios (HRs). RESULTS: Among the 80 870 pairs (63.0% girls; mean [SD] age, 12.9 [4.8] years), those who initiated PPI use had a higher incidence rate of asthma (21.8 events per 1000 person-years) compared with noninitiators (14.0 events per 1000 person-years), with an HR of 1.57 (95% CI, 1.49-1.64). The risk of asthma was significantly increased across all age groups and was highest for infants and toddlers with an HR of 1.83 (95% CI, 1.65-2.03) in the group younger than 6 months and 1.91 (95% CI, 1.65-2.22) in the group 6 months to younger than 2 years (P < .001 for interaction). The HRs for individual PPIs were 1.64 (95% CI, 1.50-1.79) for esomeprazole, 1.49 (95% CI, 1.25-1.78) for lansoprazole, 1.43 (95% CI, 1.35-1.51) for omeprazole, and 2.33 (95% CI, 1.30-4.18) for pantoprazole. In analyses of the timing of asthma onset after PPI initiation, the HRs were 1.62 (95% CI, 1.42-1.85) for 0 to 90 days, 1.73 (95% CI, 1.52-1.98) for 91 to 180 days, and 1.53 (95% CI, 1.45-1.62) for 181 days to end of follow-up. The association was consistent through all sensitivity analyses, including high-dimensional propensity score matching (HR, 1.48; 95% CI, 1.41-1.55). CONCLUSIONS AND RELEVANCE: In this cohort study, initiation of PPI use compared with nonuse was associated with an increased risk of asthma in children. Proton pump inhibitors should be prescribed to children only when clearly indicated, weighing the potential benefit against potential harm.

Studies have shown an association between use of azathioprine and increased risk of acute pancreatitis in adult inflammatory bowel disease. However, whether an association exists among paediatric patients is not known. We aimed to investigate whether use of azathioprine is associated with the risk of acute pancreatitis in children with inflammatory bowel disease.We did a nationwide register-based cohort study in Sweden (2006-16) and Denmark (2000-16). All paediatric patients (18 years of age) with inflammatory bowel disease during the study period were identified through hospital records. Episodes of incident azathioprine use and no use of any thiopurine were matched (1:1) using propensity scores, controlling for sociodemographic characteristics, comorbidities, previous treatment, indicators of disease severity, and health care use. Incident acute pancreatitis (physician-assigned diagnosis with ICD-10 code K85) occurring in the 90 days following treatment initiation were identified through outpatient and inpatient hospital records.We identified 3574 azathioprine episodes and 18 700 no-use episodes, which resulted in 3374 pairs after propensity score matching; baseline characteristics in the matched cohort were well balanced. Among the matched azathioprine episodes, mean age was 14·3 years (SD 3·1), 1854 (54·9%) were male, 1923 (57·0%) had Crohn's disease, and 1451 (43·0%) had ulcerative colitis or unclassified inflammatory bowel disease. Within the first 90 days following initiation of azathioprine, 40 acute pancreatitis events occurred (incidence rate 49·1 events per 1000 person-years) compared with six events in the no-use group (8·4 events per 1000 person-years). Azathioprine use was associated with an increased risk of acute pancreatitis (incidence rate ratio 5·82 [95% CI 2·47-13·72]; absolute difference 1·0 [95% CI 0·3-2·6] events per 100 patients) during the 90-day risk period.Use of azathioprine was associated with an increased risk of acute pancreatitis in children with inflammatory bowel disease during the first 90 days following treatment initiation, suggesting the need for regular and rigorous monitoring. The risk of acute pancreatitis needs to be considered when deciding on optimal treatment strategies.Swedish Research Council, Frimurare Barnhuset Foundation, and the Åke Wiberg Foundation.

This pharmacoepidemiology study uses Swedish and Norwegian registry data to investigate associations between fluconazole use during pregnancy and subsequent stillbirth and neonatal death.