Temporal trends in the incidence of malignancy in heart failure: a nationwide Danish study.

AIMS: Cancer and heart failure (HF) share risk factors, pathophysiological mechanisms, and possibly genetics. Improved HF survival may increase the risk of cancer due to a competing risk. Whether the incidence of cancer has increased over time in patients with HF as survival has improved is unclear. Therefore, temporal trends of new onset cancer in HF patients between 1997 and 2016 were investigated. METHODS AND RESULTS: Using Danish nationwide registers, 103 711 individuals alive, free of cancer, and aged 30-80 years 1 year after HF diagnosis (index date) were included between 1 January 1997 and 31 December 2016. A five-year incidence rate of cancer for each year after index date was calculated. The median age and proportion of women at the index date decreased with advancing calendar time [1997-2001: 70.3 interquartile range (Q1-Q3 62.5-75.7), 60.9% men; 2012-16: 67.6 (59.2-73.8), 67.5% men]. The five-year incidence rate of cancer was 20.9 and 20.2 per 1,000 person-years in 1997 and 2016, respectively. In a multivariable Cox regression model, the hazard rates between index years 1997 (reference) and 2016 were not significantly different [hazard ratio 1.09 (0.97-1.23)]. The five-year absolute risk of cancer did not change with advancing calendar year, going from 9.0% (1997-2001) to 9.0% (2012-16). Five-year cumulative incidence of survival for HF patients increased with advancing calendar year, going from 55.9% (1997-2001) to 74.3% (2012-2016). CONCLUSION: Although cancer rates during 1997-2016 have remained stable within 1-6 years after the HF diagnosis, long-term survival following a HF diagnosis has increased significantly.

Association between early detected heart failure stages and future cardiovascular and non-cardiovascular events in the elderly (Copenhagen Heart Failure Risk Study).

BACKGROUND: Early stages of heart failure (HF) are associated with an increased risk of hospitalization and increased mortality, however the course of progression and the impact of non-cardiovascular comorbidities on adverse events in elderly high-risk patients are unknown. AIM: To examine the risk of future cardiovascular (CV) and non-CV events in early stages of HF in a cohort of elderly patients (age ≥ 60 with ≥ 1 risk factor for HF and without known or clinically suspected HF). METHODS: A total of 400 patients (American Heart Association HF stage A: N = 177; stage B: N = 150; stage C: N = 73) from the Copenhagen Heart Failure Risk Study were identified and followed for the main composite outcome of a HF hospitalization (HFH), ischemic heart disease (IHD), stroke, and all-cause death, recorded within the Danish nationwide registries. Non-CV hospitalization was a secondary outcome. Absolute risk was calculated by the Aalen-Johansen estimator. RESULTS: The median follow-up time was 3.3 years, total number of events were 83, and the 3-year risk (95% confidence interval) of the main outcome was 12.8% (7.8-17.9), 22.8% (16.1-29.6) and 31.8% (21.0-42.6) for patients with stage A, B, and C, respectively. 1.1% (0.0-2.7), 3.4% (1.0-6.3) and 10.0% (2.8-16.3) experienced HFH as their first event, whereas 37.3% (30.2-44.4), 49.7% (41.6-57.8) and 54.8% (43.4-66.2) were admitted for non-CV causes as their first event. CONCLUSION: The risk of HFH, IHD, stroke and all-cause death increased with severity of HF stage, and 10% of patients with undiagnosed HF stage C were admitted for HF within 3 years. However, the risk of non-CV hospitalizations was greater compared to the risk of experiencing HFH.

Familial clustering and subsequent incidence of atrial fibrillation among first-degree relatives in Denmark.

AIMS: Atrial fibrillation (AF) is associated with increased morbidity and mortality. Determination and quantification of familial risk may help identify high-risk patients. METHODS AND RESULTS: Using Danish nationwide registry data (1978-2012), we identified all first-time AF patients (probands) in Denmark. Relatives to these probands were grouped according to proband-relation: offspring from either maternal or paternal proband, and siblings to proband. Age-specific incidence of AF for these three groups of relatives and for the general Danish population was estimated. Using the general population as reference, we calculated adjusted rate ratios (RRs) of AF in the three groups of relatives. We identified 67 310, 103 822, and 11 800 AF probands who were mothers (median age 74 years, IQR 66-81), fathers (70 years, IQR 62-78), and siblings (46 years, IQR 38-52), respectively. Among those, 133 516, 221 774, and 21 448 offspring from a maternal proband, offspring from a paternal proband, and siblings, respectively, were screened for incident AF. This was recorded in 2536 (1.9%), 2906 (1.3%), and 292 (1.4%) relatives, respectively. Compared with the general Danish population, the adjusted RRs for incident AF were 3.37 [95% confidence interval (CI) 3.21-3.53] for offspring from maternal probands, 2.81 (95% CI 2.69-2.93) for offspring from paternal probands, and 5.20 (95% CI 4.61-5.85) for siblings to sibling probands. Subgroup analyses showed increased RRs with younger aged probands. CONCLUSION: Familial AF was associated with an increased RR of AF in first-degree relatives compared with the general Danish population. This suggests that familial AF is a major risk factor for developing AF in relatives.

Age-specific mortality trends in heart failure over 25 years: a retrospective Danish nationwide cohort study.

BACKGROUND: Despite advances in heart failure care reducing mortality in clinical trials, it remains unclear whether real-life cohorts have had similar improvements in life expectancy across the age spectrum. We aimed to investigate how mortality trends changed in patients with heart failure over the past 25 years, stratified by age groups. METHODS: Using Danish nationwide registries, we identified patients with new-onset heart failure aged 18-95 years. The 5-year all-cause mortality risk and the absolute risk difference of mortality between patients with heart failure and age-matched and sex-matched heart failure-free controls were assessed using Kaplan-Meier estimates and multivariable Cox regression models. Mortality trends were analysed across five calendar periods (1996-2000, 2001-05, 2006-10, 2011-15, and 2016-20) and three age groups (<65 years, 65-79 years, and ≥80 years). FINDINGS: 194 997 patients with heart failure were included. Mortality significantly decreased from 1996-2000 (66% [95% CI 65·5-66·4]) to 2016-20 (43% [42·1-43·4]), with similar results shown in all age groups (<65 years: 35% [33·9-36·1] to 15% [14·6-16·3]; 65-79 years: 64% [63·1-64·5] to 39% [37·6-39·6]; and ≥80 years: 84% [83·1-84·3] to 73% [71·7-73·9]). Adjusted mortality rates supported these associations. The absolute risk difference declined notably in younger age groups (<65 years: 29·9% [28·8-31·0] to 12·7% [12·0-13·4] and 65-79 years: 41·1% [40·3-41·9] to 25·1% [24·4-25·8]), remaining relatively stable in those aged 80 years or older (30·6% [29·9-31·3] to 28% [27·2-28·8]). INTERPRETATION: Over 25 years, there has been a consistent decrease in mortality among patients with heart failure across age groups, albeit less prominently in patients aged 80 years or older. Further insight is needed to identify effective strategies for improving disease burden in older patients with heart failure. FUNDING: None. TRANSLATION: For the Danish translation of the abstract see Supplementary Materials section.

Temporal trends in mortality, heart failure hospitalisation, and stroke in heart failure patients with and without atrial fibrillation: a nationwide study from 1997-2018 on 152,059 patients.

AIMS: We aimed to investigate temporal trends in all-cause mortality, heart failure (HF) hospitalisation, and stroke from 1997 to 2018 in patients diagnosed with both HF and atrial fibrillation (AF). METHODS AND RESULTS: From Danish nationwide registers, we identified 152 059 patients with new-onset HF between 1997 and 2018. Patients were grouped according to year of new-onset HF and AF-status: Prevalent AF (n = 34 734), New-onset AF (n = 12 691), and No AF (n = 104 634). Median age decreased from 76 to 73 years between 1997 and 2018. The proportion of patients with prevalent or new-onset AF increased from 24.7% (n = 9256) to 35.8% (n = 14 970). Five-year risk of all-cause mortality went from 69.1% (CI: 67.9%-70.2%) to 51.3% (CI: 49.9%-52.7%), 62.3% (CI: 60.5%-64.4%) to 43.0% (CI: 40.5%-45.5%), and 61.9% (CI: 61.3%-62.4%) to 36.7% (CI: 35.9%-37.6%) for the Prevalent AF, New-onset AF and No AF-group, respectively. Minimal changes were observed in the risk of HF-hospitalisation. Five-year stroke risk decreased from 8.5% (CI: 7.8%-9.1%) to 5.0% (CI: 4.4%-5.5%) for the prevalent AF group, 8.2% (CI: 7.2%-9.2%) to 4.6% (CI: 3.7%-5.5%) for new-onset AF, and 6.3% (CI: 6.1%-6.6%) to 4.9% (CI: 4.6%-5.3%) for the No AF group. Simultaneously, anticoagulant therapy increased for patients with prevalent (from 42.7% to 93.1%) and new-onset AF (from 41.9% to 92.5%). CONCLUSION: From 1997 to 2018, we observed an increase in patients with HF and co-existing AF. Mortality decreased for all patients, regardless of AF-status. Anticoagulation therapy increased, and stroke risk for patients with AF was reduced to a similar level as patients without AF in 2013-2018.

Excess long-term risk of adverse outcomes in heart failure patients with high and low levels of NT-proBNP: A 7-year follow-up study (NorthStar Trial).

Background: This study investigated excess risk in patients with heart failure with reduced left ventricular ejection fraction (HFrEF) with or without elevated levels of NT-proBNP (N-terminal pro-brain natriuretic peptide). Methods: Patients with HFrEF from the NorthStar cohort (n = 1120) were matched on age, sex, and presence of AF (atrial fibrillation/flutter) to five controls without HFrEF from The Danish National Patient Registries. Patients were compared with controls before and after stratification according to baseline NT-proBNP levels, with cutoffs defined as

Temporal Trends in the Initiation of Dialysis Among Patients With Heart Failure With or Without Diabetes: A Nationwide Study From 2002 to 2016.

BACKGROUND: The incidence and distribution of acute and chronic dialysis among patients with heart failure (HF), stratified by diabetes, remain uncertain. We hypothesized that with improved survival and rising comorbidities, the demand for dialysis would increase over time. METHODS AND RESULTS: Patients with incident HF, aged 18 to 100 years, between 2002 and 2016, were identified using Danish nationwide registers. Primary outcomes included acute and chronic dialysis initiation, HF-related hospitalization, and all-cause mortality. These outcomes were assessed in 2002 to 2006, 2007 to 2011, and 2012 to 2016, stratified by diabetes. We calculated incidence rates (IRs) per 1000 person-years and hazard ratios (HR) using multivariable Cox regression. Of 115 533 patients with HF, 2734 patients received acute dialysis and 1193 patients received chronic dialysis. The IR was 8.0 per 1000 and 3.5 per 1000 person-years for acute and chronic dialysis, respectively. Acute dialysis rates increased significantly among patients with diabetes over time, while no significant changes occurred in those without diabetes, chronic dialysis, HF-related hospitalization, or overall mortality. Diabetes was associated with significantly higher HRs of acute and chronic dialysis, respectively, compared with patients without diabetes (HR, 2.07 [95% CI, 1.80-2.39] and 2.93 [95% CI, 2.40-3.58] in 2002 to 2006; HR, 2.45 [95% CI, 2.14-2.80] and 2.86 [95% CI, 2.32-3.52] in 2007 to 2011; and 2.69 [95% CI, 2.33-3.10] and 3.30 [95% CI, 2.69-4.06] in 2012 to 2016). CONCLUSIONS: The IR of acute and chronic dialysis remained low compared with HF-related hospitalizations and mortality. Acute dialysis rates increased significantly over time, contrasting no significant trends in other outcomes. Diabetes exhibited over 2-fold increased rates of the outcomes. These findings emphasize the importance of continued monitoring and renal care in patients with HF, especially with diabetes, to optimize outcomes and prevent adverse events.

Initiation of SGLT2 inhibitors and GLP-1 receptor agonists according to level of frailty in people with type 2 diabetes and cardiovascular disease in Denmark: a cross-sectional, nationwide study.

BACKGROUND: Whether frailty influences the initiation of two cardioprotective diabetes drug therapies (ie, SGLT2 inhibitors and GLP-1 receptor agonists) in people with type 2 diabetes and cardiovascular disease is unknown. We aimed to assess rates of initiation of SGLT2 inhibitors and GLP-1 receptor agonists according to frailty in people with type 2 diabetes and cardiovascular disease. METHODS: For this cross-sectional, nationwide study, all people with type 2 diabetes and cardiovascular disease in Denmark between Jan 1, 2015, and Dec 31, 2021, from six Danish health-data registers were identified. People younger than 40 years, with end-stage renal disease, with registered contraindications to SGLT2 inhibitors or GLP-1 receptor agonists, or with previous use of either drug therapy were excluded. The Hospital Frailty Risk Score was used to categorise people as either non-frail, moderately frail, or severely frail. Cox proportional hazards models were used to analyse the association between frailty and initiation of an SGLT2 inhibitor or a GLP-1 receptor agonist. FINDINGS: Of 119 390 people with type 2 diabetes and cardiovascular disease, 103 790 were included. Median follow-up time was 4·5 years (IQR 2·7-6·1) and median age across the three frailty groups was 71 years (64-79). 65 959 (63·6%) of 103 790 people were male and 37 831 (36·5%) were female. At index date, 66 910 (64·5%) people were non-frail, 29 250 (28·2%) were moderately frail, and 7630 (7·4%) were severely frail. Frailty was associated with a significantly lower probability of initiating therapy with an SGLT2 inhibitor or a GLP-1 receptor agonist than in people who were non-frail (moderately frail hazard ratio 0·91, 95% CI 0·88-0·94, p<0·0001; severely frail 0·75, 0·70-0·80, p<0·0001). This association persisted after adjustment for age, sex, socioeconomic status, year of inclusion, duration of type 2 diabetes, duration of cardiovascular disease, polypharmacy, and comorbidity. INTERPRETATION: In people with type 2 diabetes and cardiovascular disease in Denmark, frailty was associated with a significantly lower probability of SGLT2-inhibitor or GLP-1 receptor-agonist initiation, despite their benefits. Formulating clear and updated guidelines on the use of SGLT2 inhibitors and GLP-1 receptor agonists in people who are frail with type 2 diabetes and cardiovascular disease should be a priority. FUNDING: Department of Cardiology, Herlev and Gentofte University Hospital. TRANSLATION: For the Danish translation of the abstract see Supplementary Materials section.

Discontinuation and reinitiation of SGLT-2 inhibitors and GLP-1R agonists in patients with type 2 diabetes: a nationwide study from 2013 to 2021.

Background: Small observational studies have observed poor persistency to sodium-glucose cotransporter-2 inhibitors (SGLT2-i) and glucacon-like-peptide-1-receptor agonists (GLP1-RA), contrary to what has been reported in clinical trials. Therefore, we investigated the risk of discontinuing SGLT2-is and GLP1-RAs in patients with type 2 diabetes (T2D) in a nationwide population. Methods: From Danish nationwide registers, all first-time users of SGLT2-is and GLP1-RAs from 2013 to 2021 were identified. Adherence over the first year of therapy, the five-year risk of discontinuing therapy for the first time and the subsequent one-year probability of reinitiating therapy, was assessed. The Aalen-Johansen estimator was used to account for censoring and competing risks and multivariable Cox regression models were used to identify covariates associated with discontinuation. Findings: A total of 77,745 first-time users of SGLT2-is (64% male, median age 64 [interquartile range 56-72]) and 56,037 first-time users of GLP1-RAs (56% male, median age 61 [53-70]) were included. The absolute five-year risk of discontinuing therapy was 56% (95% CI: 55-57) and 45% (45-46) for SGLT2-i- and GLP1-RA users, respectively, with a significantly decreased risk over the period studied. The subsequent one-year probability of reinitiating therapy was 24% (95% CI: 24-25) for initial SGLT2-i users and 26% (25-27) for GLP1-RA users. Interpretation: Approximately half of the users of SGLT2-is and GLP1-RAs discontinued therapy within five years, respectively. However, a large proportion of these patients reinitiated therapy during the following year. Further insight into the reasons for discontinuation and initiatives to reduce the time to reinitiation in eligible patients are warranted. Funding: The work was funded by an unrestricted research grant from 'Department of Cardiology, Herlev and Gentofte University Hospital'.

Specialized heart failure clinics versus primary care: Extended registry-based follow-up of the NorthStar trial.

BACKGROUND: Whether continued follow-up in specialized heart failure (HF) clinics after optimization of guideline-directed therapy improves long-term outcomes in patients with HF with reduced ejection fraction (HFrEF) is unknown. METHODS AND RESULTS: 921 medically optimized HFrEF patients enrolled in the NorthStar study were randomly assigned to follow up in a specialized HF clinic or primary care and followed for 10 years using Danish nationwide registries. The primary outcome was a composite of HF hospitalization or cardiovascular death. We further assessed the 5-year adherence to prescribed neurohormonal blockade in 5-year survivors. At enrollment, the median age was 69 years, 24,7% were females, and the median NT-proBNP was 1139 pg/ml. During a median follow-up time of 4.1 (Q1-Q3 1.5-10.0) years, the primary outcome occurred in 321 patients (69.8%) randomized to follow-up in specialized HF clinics and 325 patients (70.5%) randomized to follow-up in primary care. The rate of the primary outcome, its individual components, and all-cause death did not differ between groups (primary outcome, hazard ratio 0.96 [95% CI, 0.82-1.12]; cardiovascular death, 1.00 [0.81-1.24]; HF hospitalization, 0.97 [0.82-1.14]; all-cause death, 1.00 [0.83-1.20]). In 5-year survivors (N = 660), the 5-year adherence did not differ between groups for angiotensin-converting enzyme inhibitors (p = 0.78), beta-blockers (p = 0.74), or mineralocorticoid receptor antagonists (p = 0.47). CONCLUSIONS: HFrEF patients on optimal medical therapy did not benefit from continued follow-up in a specialized HF clinic after initial optimization. Development and implementation of new monitoring strategies are needed.

A Composite Score Summarizing Use and Dosing of Evidence-Based Medical Therapies in Heart Failure: A Nationwide Cohort Study.

BACKGROUND: As heart failure therapeutic care becomes increasingly complex, a composite medical therapy score could be useful to conveniently summarize background medical therapy. We applied the composite medical therapy score developed by the Heart Failure Collaboratory (HFC) to the Danish heart failure with reduced ejection fraction population to evaluate its external validation including assessing the distribution of the score and its association with survival. METHODS: In a retrospective nationwide cohort study, we identified all Danish heart failure with reduced ejection fraction patients alive on July 1, 2018, and assessed their treatment doses. Patients were excluded if they did not have at least 365 days for up-titration of medical therapy prior to identification. The HFC score (range 0-8) accounts for use and dosing of multiple therapies prescribed to each patient. Risk-adjusted association between the composite score and all-cause mortality was examined. RESULTS: In total, 26 779 patients (mean age 71.9 years; 32% women) were identified. At baseline, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker was used in 77%, ß-blocker in 81%, mineralocorticoid receptor antagonist in 30%, angiotensin receptor-neprilysin inhibitor in 2%, and ivabradine in 2%. The median HFC score was 4. After multivariable adjustment, higher HFC scores were independently associated with lower mortality (≥median versus

Temporal trends in initiation of mineralocorticoid receptor antagonists and risk of subsequent withdrawal in patients with heart failure: a nationwide study in Denmark from 2003-2017.

AIMS: Despite landmark heart failure (HF) with reduced ejection fraction (HFrEF) trials showing effect of mineralocorticoid receptor antagonists (MRA) on the risk of death and HF hospitalization, it has been suggested that MRAs are underutilized or frequently withdrawn. This study sought to identify temporal trends in the initiation of MRAs and the subsequent risk of withdrawal and adherence of MRAs in HF patients treated with a renin-angiotensin system inhibitor and a beta-blocker in Denmark from 2003-2017. METHODS AND RESULTS: From nationwide registries, we identified patients receiving a diagnosis of HF. Use of MRA was identified by at least one prescription within 6 months after the diagnosis. The absolute risk of withdrawal with treatment was assessed with cumulative incidence, accounting for the competing risk of death. To estimate adherence, we calculated the proportion of days covered. We included 51 512 patients with incident HF. During the study period, 20 779 (40.3%) patients initiated MRA therapy. The incidence of withdrawal of MRA was 49.2% throughout the study period; 48.0% of the HF patients were adherent to the treatment. Among patients withdrawing treatment with MRA, the cumulative incidence of reinitiating was 36.6%. CONCLUSIONS: In a nationwide cohort of patients with HF, approximately half of the patients received MRA as third-line therapy within the first 6 months after diagnosis and approximately half of these withdrew MRA within 5 years. These findings warrant an increasing focus on retention to MRA treatment in a real-life setting.

Adherence and Discontinuation of Optimal Heart Failure Therapies According to Age: A Danish Nationwide Study.

Background Guideline-recommended disease-modifying pharmacological therapies for heart failure (HF) with reduced ejection fraction are underutilized, particularly among elderly patients. We studied the association of age in adherence and discontinuation of angiotensin-converting enzyme inhibitors/angiotensin-II receptor blockers (ACEi/ARB), ß-blockers (BB), and mineralocorticoid receptor antagonists. Methods and Results Patients with a first heart failure diagnosis who had initiated ACEi/ARB and BB within 120 days of presentation were included from nationwide registries and divided into 3 age groups: <65 years (reference), 65 to 79, and ≥80. One-year median proportions of daily target doses were calculated. Adherence was estimated by the proportion of days covered. The 5-year risk of discontinuation was assessed with the Aalen-Johansen estimator. Discontinuation rates were evaluated using Multivariable Cox regression. Twenty-nine thousand four hundred eighty-two patients were included. Advancing age was associated with lower median proportions of daily target doses and adherence (ACEi/ARB 79.1%, 77.5%, and 69.4%; BB 79.1%, 78.6%, and 73.8%), in the <65, 65 to 79, and ≥80 age groups, respectively. Age ≥80 was associated with higher discontinuation rates (cumulative incidence, ACEi/ARB 41%, 44%, and 51%; BB 38%, 35%, and 39%; hazard ratio, ACEi/ARB 1.60 [95% CI, 1.51-1.69]; BB 1.33 [95% CI, 1.25-1.41]). The risk of mineralocorticoid receptor antagonists discontinuation differed little with age (50%, 54%, and 56%), although mineralocorticoid receptor antagonists initiation in the most elderly was less frequent (33%, 33%, and 22%). Conclusions In a nationwide cohort of patients with heart failure, advanced age was associated with lower proportions of daily target doses, lower adherence, and higher discontinuation rates of ACEi/ARB and BBs. Focus on treatment adherence and optimal dosages among elderly patients with heart failure could improve outcomes.

Importance of diagnostic setting in determining mortality in patients with new-onset heart failure: temporal trends in Denmark from 1997 to 2017.

AIM: To investigate temporal trends in inpatient vs. outpatient diagnosis of new-onset heart failure (HF) and the subsequent risk of death and hospitalization. METHODS AND RESULTS: Using nationwide registers, 192 581 patients with a first diagnosis of HF (1997-2017) were included. We computed incidences of HF, age-standardized mortality rates, and absolute risks (ARs) of death and hospitalization (accounting for competing risk of death) to understand the importance of the diagnosis setting in relation to subsequent mortality and hospitalization. The overall incidence of HF was approximately the same (170/100 000 persons) every year during 1997-2017. However, in 1997, 77% of all first diagnoses of HF were made during a hospitalization, whereas the proportion was 39% in 2017. As inpatient diagnoses decreased, outpatient diagnoses increased from 23% to 61%. Outpatients had lower mortality and hospitalization rates than inpatients throughout the study period, although the 1-year age-standardized mortality rate decreased for each inpatient (24 to 14/100-person) and outpatient (11 to 7/100-person). One-year and five-year AR of death decreased by 11.1% and 17.0%, respectively, for all HF patients, while the risk of hospitalization for HF did not decrease significantly (1.13% and 0.96%, respectively). CONCLUSION: Between 1997 and 2017, HF changed from being primarily diagnosed during hospitalization to being mostly diagnosed in the outpatient setting. Outpatients had much lower mortality rates than inpatients throughout the study period. Despite a significant decrease in mortality risk for all HF patients, neither inpatients nor outpatients experienced a reduction in the risk of an HF hospitalization.

Syncope and Motor Vehicle Crash Risk: A Danish Nationwide Study.

IMPORTANCE: Syncope may have serious consequences for traffic safety. Current clinical guideline recommendations on driving following syncope are primarily based on expert consensus. OBJECTIVE: To identify whether there is excess risk of motor vehicle crashes among patients with syncope compared with the general population. DESIGN, SETTING, AND PARTICIPANTS: Danish nationwide cohort study from January 1, 2008, to December 31, 2012. Through individual-level linkage of nationwide administrative registers, all Danish residents 18 years or older were identified. Of 4 265 301 eligible Danish residents, we identified 41 039 individuals with a first-time diagnosis of syncope from emergency department or hospital. MAIN OUTCOMES AND MEASURES: Rate of motor vehicle crashes (including nonfatal and fatal crashes), based on multivariate Poisson regression models, using the total Danish population as reference. RESULTS: The 41 039 patients with syncope had a median age of 66 years (interquartile range [IQR], 47-78 years); 51.0% were women; and 34.8% had cardiovascular disease. Through a median follow-up of 2.0 years (IQR, 0.8-3.3 years), 1791 patients with syncope (4.4%) had a motor vehicle crash, 78.1% of which led to injury (n = 1398) and 0.3% to death (n = 6). The crude incidence rate of motor vehicle crashes was almost doubled among patients with syncope (20.6 per 1000 person-years; 95% CI, 19.7-21.6) compared with the general population (12.1; 95% CI, 12.0-12.1), with a rate ratio (RR) of 1.83 (95% CI, 1.74-1.91) after adjustment for age, sex, socioeconomic position, and relevant comorbidities and pharmacotherapy. Men had a relatively higher rate of motor vehicle crashes (RR, 1.91; 95% CI, 1.79-2.03) than women (RR, 1.74; 95% CI, 1.63-1.87). The excess risk of motor vehicle crashes persisted throughout the follow-up period. The 5-year crash risk following syncope was 8.2% (95% CI, 7.5%-8.8%) among the population aged 18 to 69 years compared with 5.1% (95% CI, 4.7%-5.4%) in the general population. CONCLUSIONS AND RELEVANCE: Prior hospitalization for syncope was associated with increased risk of motor vehicle crashes throughout the follow-up period. This study suggests that syncope should be considered as one of several factors in a broad assessment of fitness to drive.