Point: incident exposures, prevalent exposures, and causal inference: does limiting studies to persons who are followed from first exposure onward damage epidemiology?

Ethnic differences in depression and anxiety among adults with atopic eczema: Population-based matched cohort studies within UK primary care

BACKGROUND

Evidence demonstrates that individuals with atopic eczema (eczema) have increased depression and anxiety; however, the role of ethnicity in these associations is poorly understood. We aimed to investigate whether associations between eczema and depression or anxiety differed between adults from white and minority ethnic groups in the UK.

METHODS

We used UK Clinical Practice Research Datalink GOLD to conduct matched cohort studies of adults (≥18 years) with ethnicity recorded in primary care electronic health records (April 2006-January 2020). We matched (age, sex, practice) adults with eczema to up to five adults without. We used stratified Cox regression with an interaction between eczema and ethnicity, to estimate hazard ratios (HRs) for associations between eczema and incident depression and anxiety in individuals from white ethnic groups and a pooled minority ethnic group (adults from Black, South Asian, Mixed and Other groups).

RESULTS

We identified separate cohorts for depression (215,073 with eczema matched to 646,539 without) and anxiety (242,598 with eczema matched to 774,113 without). After adjusting for matching variables and potential confounders (age, sex, practice, deprivation, calendar period), we found strong evidence (p < 0.01) of ethnic differences in associations between eczema and depression (minority ethnic groups: HR = 1.33, 95% CI = 1.22,1.45; white ethnic groups: HR = 1.15, 95% CI = 1.12,1.17) and anxiety (minority ethnic groups: HR = 1.41, 95% CI = 1.28,1.55; white ethnic groups: HR = 1.17, 95% CI = 1.14,1.19).

CONCLUSIONS

Adults with eczema from minority ethnic groups appear to be at increased depression and anxiety risk compared with their white counterparts. Culturally adapted mental health promotion and prevention strategies should be considered in individuals with eczema from minority ethnic groups.

Widening Excess Mortality During the COVID-19 Pandemic in Individuals Who Self-Harmed

Background: Studies on COVID-19 pandemic-associated changes in mortality following self-harm remain scarce and inconclusive. Aims: To compare mortality risks in individuals who had self-harmed to those for individuals who had not, before and during the COVID-19 pandemic (Waves 1 and 2) in Wales, the United Kingdom, using population-based routinely collected data. Method: We linked whole population health data to all-cause mortality following an episode of self-harm between April 2016 and March 2021. Propensity score matching, Cox regression, and difference-in-differences were applied to compute changes in excess mortality (as ratios of hazard ratios, RHRs) before and during the pandemic for individuals who self-harmed. Results: The difference in mortality for individuals who self-harmed compared to those who did not widened during Wave 1 (RHR = 2.03, 95% CI: 1.04-4.03) and Wave 2 (RHR = 2.19, 95% CI: 1.12-4.29) from before the pandemic. Stratification by sex and age group produced no significant subgroup differences although risk for younger than 65 years group were higher. Limitations: Limitations include small sample size and incomplete data on cause-specific deaths during the pandemic. Conclusion: Our results underscore continuous monitoring of mortality of individuals who self-harm and effective interventions to address any increases in mortality.

Depression and anxiety-related disorders and suicide among Swedish male elite football players: a nationwide cohort study

OBJECTIVE

To assess whether male elite football players, during and after their active career, were at increased risk of depression and anxiety-related disorders and suicide, as compared with the general male population.

METHODS

We included male football players active in the Swedish top division 1924-2019 and general male population (matched to football players based on age and region of residence) aged <65 years in 1997. Using nationwide registers, we followed the football players from their first season in the top division (or the date of their first registered residency in Sweden) or 1 January 1997, and compared the risk of depression and anxiety-related disorders (captured through diagnoses from hospital admissions and outpatient visits, and use of prescription drugs) among football players versus controls. In a secondary analysis using data from death certificates, we compared the risk of suicide between football players and general population males who were alive in 1969 (when cause of death became available) .

RESULTS

During follow-up through 31 December 2020, 504 (13.6%) of 3719 football players and 7455 (22.3%) of 33 425 general population males had a depression or anxiety-related disorder. In analyses accounting for age, region of residence and calendar time, the risk of anxiety and depression-related disorders was lower among football players versus general population males (HR 0.61, 95% CI 0.55 to 0.66). The protective association was attenuated with increasing age, and from around age 70 years the risk was similar in the two groups. The risk of suicide was lower among football players versus general population males (HR 0.48, 95% CI 0.32 to 0.72).

CONCLUSIONS

In this nationwide cohort study in Sweden, elite male football players had a lower risk of depression and anxiety-related disorders and suicide as compared with the general population.

Addressing the unique challenges in studies of long-term medication use and dementia risk

This editorial comments on the article by Wu et al. in this issue.

Dopamine agonists and risk of lung cancer in patients with restless legs syndrome

PURPOSE

To examine the association between long-term use of dopamine agonists (DAs) and the risk of lung cancer in patients with restless legs syndrome (RLS).

METHODS

We conducted a retrospective cohort study using Optum Clinformatics® database. We included adults ≥40 years diagnosed with RLS during the study period (1/2006-12/2016). Follow-up started with the first RLS diagnosis and ended on the earliest of: incident diagnosis of lung cancer, end of enrollment in the database or end of the study period. The exposure of interest was cumulative duration of DAs use, measured in a time-varying manner. We constructed a multivariable Cox regression model to estimate HRs and 95% CIs for the association between lung cancer and cumulative durations of DA use, adjusting for potential confounding variables.

RESULTS

We identified 295 042 patients with a diagnosis of RLS. The mean age of the cohort was 62.9; 66.6% were women and 82.3% were white. The prevalence of any DA exposure was 40.3%. Compared to the reference group (no use and ≤1 year), the crude HRs for lung cancer were 1.16 (95% CI 0.99-1.36) and 1.14 (95% CI 0.86-1.51) for 1-3 years and >3 years of cumulative DA use, respectively. The adjusted HR for lung cancer was 1.05 (95% CI 0.88-1.25) for 1-3 years and 1.02 (95% CI 0.76-1.37) for >3 years of cumulative DA use, respectively.

CONCLUSIONS

At typical doses for the clinical management of RLS, long-term DA use was not associated with risk of lung cancer.

Neurodegenerative disease among male elite football (soccer) players in Sweden: a cohort study

BACKGROUND

Football (soccer) players might be at increased risk of neurodegenerative disease, which has led to questions regarding the safety of the sport and recent measures introduced by football associations to reduce heading of the ball. We aimed to assess the risk of neurodegenerative disease among male football players in the Swedish top division Allsvenskan, compared with matched controls.

METHODS

In this cohort study, we identified all male football players (amateurs and professionals) who had played at least one game in Allsvenskan from Aug 1, 1924 to Dec 31, 2019 and excluded players whose personal identity number could not be retrieved or be identified in the Total Population Register, and those who were not born in Sweden and who had immigrated to the country after age 15 years. Football players were matched with up to ten controls from the general population according to sex, age, and region of residence. We used nationwide registers to compare the risk of neurodegenerative disease (diagnoses recorded in death certificates, during hospital admissions and outpatient visits, or use of prescription drugs for dementia) among football players versus controls. We also assessed each type of neurodegenerative disease (Alzheimer's disease and other dementias, motor neuron disease, and Parkinson's disease) separately, and compared the risk of neurodegenerative disease among outfield players versus goalkeepers.

FINDINGS

Of 7386 football players who had played at least one game in the top Swedish division between Aug 1, 1924, and Dec 31, 2019, 182 players were excluded for an unretrievable personal identity number, and 417 were excluded due to their number not being identified in the Total Population Register. After a further exclusion of 780 players and 11 627 controls who were born outside of Sweden and who had immigrated to the country after age 15 years, 6007 football players (510 goalkeepers) were included in the study population along with 56 168 matched controls. During follow-up to Dec 31, 2020, 537 (8·9%) of 6007 football players and 3485 (6·2%) of 56 168 controls were diagnosed with neurodegenerative disease. The risk of neurodegenerative disease was higher among football players than controls (hazard ratio [HR] 1·46 [95% CI 1·33-1·60]). Alzheimer's disease and other dementias were more common among football players than controls (HR 1·62 [95% CI 1·47-1·78]), significant group differences were not observed for motor neuron disease (HR 1·27 [0·73-2·22]), and Parkinson's disease was less common among football players (HR 0·68 [0·52-0·89]). The risk of neurodegenerative disease was higher for outfield players than controls (HR 1·50 [95% CI 1·36-1·65]) but not for goalkeepers versus controls (HR 1·07 [0·78-1·47]), and outfield players had a higher risk of neurodegenerative disease than did goalkeepers (HR 1·43 [1·03-1·99]). All-cause mortality was slightly lower among football players than controls (HR 0·95 [95% CI 0·91-0·99]).

INTERPRETATION

In this cohort study, male football players who had played in the Swedish top division had a significantly increased risk of neurodegenerative disease compared with population controls. The risk increase was observed for Alzheimer's disease and other dementias but not for other types of neurodegenerative disease, and among outfield players, but not among goalkeepers. Our study expands on the data that can be used to assess and manage risks in the sport.

FUNDING

Karolinska Institutet, The Swedish Research Council for Sport Science, Folksam Research Foundation, Hedberg Foundation, Neurofonden, and Åhlen Foundation.

Severe Mental Illness Among Adults with Atopic Eczema or Psoriasis: Population-Based Matched Cohort Studies within UK Primary Care

Background

Existing research exploring associations between atopic eczema (AE) or psoriasis, and severe mental illness (SMI - ie, schizophrenia, bipolar disorder, other psychoses) is limited, with longitudinal evidence particularly scarce. Therefore, temporal directions of associations are unclear. We aimed to investigate associations between AE or psoriasis and incident SMI among adults.

Methods

We conducted matched cohort studies using primary care electronic health records (January 1997 to January 2020) from the UK Clinical Practice Research Datalink GOLD. We identified two cohorts: 1) adults (≥18 years) with and without AE and 2) adults with and without psoriasis. We matched (on age, sex, general practice) adults with AE or psoriasis with up to five adults without. We used Cox regression, stratified by matched set, to estimate hazard ratios (HRs) comparing incident SMI among adults with and without AE or psoriasis.

Results

We identified 1,023,232 adults with AE and 4,908,059 without, and 363,210 with psoriasis and 1,801,875 without. After adjusting for matching variables (age, sex, general practice) and potential confounders (deprivation, calendar period) both AE and psoriasis were associated with at least a 17% increased hazard of SMI (AE: HR=1.17,95% CI=1.12-1.22; psoriasis: HR=1.26,95% CI=1.18-1.35). After additionally adjusting for potential mediators (comorbidity burden, harmful alcohol use, smoking status, body mass index, and, in AE only, sleep problems and high-dose glucocorticoids), associations with SMI did not persist for AE (HR=0.98,95% CI=0.93-1.04), and were attenuated for psoriasis (HR=1.14,95% CI=1.05-1.23).

Conclusion

Our findings suggest adults with AE or psoriasis are at increased risk of SMI compared to matched comparators. After adjusting for potential mediators, associations with SMI did not persist for AE, and were attenuated for psoriasis, suggesting that the increased risk may be explained by mediating factors (eg, sleep problems). Our research highlights the importance of monitoring mental health in adults with AE or psoriasis.

Alcohol related disorders among elite male football players in Sweden: nationwide cohort study

OBJECTIVES

To assess whether male elite football players are at increased risk of alcohol related disorders compared with men from the general population, and whether such an increased risk would vary on the basis of calendar year of the first playing season in the top tier of competition, age, career length, and goal scoring abilities.

DESIGN

Nationwide cohort study.

SETTING

Sweden, 1924-2020.

PARTICIPANTS

6007 male football players who had played in the Swedish top division, Allsvenskan, from 1924 to 2019 and 56 168 men from the general population matched to players based on age and region of residence.

MAIN OUTCOME MEASURES

Primary outcome was alcohol related disorders (diagnoses recorded in death certificates, during hospital admissions and outpatient visits, or use of prescription drugs for alcohol addiction); secondary outcome was disorders related to misuse of other drugs.

RESULTS

During follow-up up to 31 December 2020, 257 (4.3%) football players and 3528 (6.3%) men from the general population received diagnoses of alcohol related disorders. In analyses accounting for age, region of residence, and calendar time, risk of alcohol related disorders was lower among football players than among men from the general population (hazard ratio 0.71, 95% confidence interval 0.62 to 0.81). A reduced risk of alcohol related disorders was observed for football players who played their first season in the top tier in the early 1960s and later, while no significant difference versus men from the general population was seen in the risk for football players from earlier eras. The hazard ratio was lowest at around age 35 years, and then increased with age; at around age 75 years, football players had a higher risk of alcohol related disorders than men from the general population. No significant association was seen between goal scoring, number of games, and seasons played in the top tier and the risk of alcohol related disorders. Risk of disorders related to other drug misuse was significantly lower among football players than the general population (hazard ratio 0.22, 95% confidence interval 0.15 to 0.34).

CONCLUSIONS

In this nationwide cohort study, male football players who had played in the Swedish top tier of competition had a significantly lower risk of alcohol related disorders than men from the general population.

A review of decision aids to assess cardiovascular risk

PURPOSE OF REVIEW

Cardiovascular disease remains one of the leading causes of morbidity and mortality today. The major risk factors for cardiovascular disease include type 2 diabetes mellitus, hypertension, tobacco smoking, elevated body mass index, and hyperlipidemia. The decision to use medication treatment for hyperlipidemia can be assisted using computerized decision tools.

RECENT FINDINGS

The treatment of hyperlipidemia with 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has become widely recommended even though most people treated with them do not get clinical benefit, and the magnitude of their effect is dependent upon prior clinical risk. This article reviews recent research about the effectiveness of HMG-CoA reductase inhibitors, and the use of decision-making tools to assist the clinician in advising patients about the use of these medications.

SUMMARY

On-line decision tools are available to estimate cardiovascular risk and to assist clinicians in helping their patients make their own decision about whether to take HMG-CoA reductase inhibitor medication to reduce cardiovascular risk.

Atopic Eczema-Associated Fracture Risk and Oral Corticosteroids: A Population-Based Cohort Study

BACKGROUND

Evidence suggests adults with atopic eczema have increased fracture risk. However, it is unclear whether oral corticosteroids explain the association.

OBJECTIVE

To assess to what extent oral corticosteroids mediate the relationship between atopic eczema and fractures.

METHODS

We conducted a cohort study using English primary care (Clinical Practice Research Datalink) and hospital admissions (Hospital Episode Statistics) records (1998-2016) including adults (18 years old and older) with atopic eczema matched (age, sex, and general practice) with up to 5 adults without atopic eczema. We used Cox regression to estimate hazard ratios (HRs) for specific major osteoporotic fractures (hip, spine, pelvis, or wrist) and for any-site fracture comparing individuals with atopic eczema with those without, adjusting for 6 different definitions of time-updated oral corticosteroid use (ever any prescription, ever high-dose, and recent, cumulative, current, or peak dose).

RESULTS

We identified 526,808 individuals with atopic eczema and 2,569,030 without. We saw evidence of an association between atopic eczema and major osteoporotic fractures (eg, spine HR 1.15, 99% CI 1.08-1.22; hip HR 1.11, 99% CI 1.08-1.15) that remained after additionally adjusting for oral corticosteroids (eg, cumulative corticosteroid dose: spine HR 1.09, 99% CI 1.03-1.16; hip HR 1.09, 99% CI 1.06-1.12). Fracture rates were higher in people with severe atopic eczema than in people without even after adjusting for oral corticosteroids (eg, spine HR [99% CI]: confounder-adjusted 2.31 [1.91-2.81]; additionally adjusted for cumulative dose 1.71 [1.40-2.09]).

CONCLUSIONS

Our findings suggest that little of the association between atopic eczema and major osteoporotic fractures is explained by oral corticosteroid use.

The impact of left truncation of exposure in environmental case-control studies: evidence from breast cancer risk associated with airborne dioxin

In epidemiology, left-truncated data may bias exposure effect estimates. We analyzed the bias induced by left truncation in estimating breast cancer risk associated with exposure to airborne dioxins. Simulations were run with exposure estimates from a Geographic Information System (GIS)-based metric and considered two hypotheses for historical exposure, three scenarios for intra-individual correlation of annual exposures, and three exposure-effect models. For each correlation/model combination, 500 nested matched case-control studies were simulated and data fitted using a conditional logistic regression model. Bias magnitude was assessed by estimated odds-ratios (ORs) versus theoretical relative risks (TRRs) comparisons. With strong intra-individual correlation and continuous exposure, left truncation overestimated the Beta parameter associated with cumulative dioxin exposure. Versus a theoretical Beta of 4.17, the estimated mean Beta (5%; 95%) was 73.2 (67.7; 78.8) with left-truncated exposure and 4.37 (4.05; 4.66) with lifetime exposure. With exposure categorized in quintiles, the TRR was 2.0, the estimated OR_{Q5 vs. Q1} 2.19 (2.04; 2.33) with truncated exposure versus 2.17 (2.02; 2.32) with lifetime exposure. However, the difference in exposure between Q5 and Q1 was 18× smaller with truncated data, indicating an important overestimation of the dose effect. No intra-individual correlation resulted in effect dilution and statistical power loss. Left truncation induced substantial bias in estimating breast cancer risk associated with exposure with continuous and categorical models. With strong intra-individual exposure correlation, both models detected associations, but categorical models provided better estimates of effect trends. This calls for careful consideration of left truncation-induced bias in interpreting environmental epidemiological data.

Cardiovascular events and mortality in people with and without type 2 diabetes: An observational study in a contemporary multi-ethnic population

AIMS/INTRODUCTION

The aim of this study was to examine ethnicity-specific associations between type 2 diabetes mellitus and the risk of a cardiovascular disease (CVD) event as well as risk of specific CVD phenotypes in England.

METHODS

We obtained data from the Clinical Practice Research Datalink for adults with and without type 2 diabetes mellitus diagnosed 2000-2006. The outcome was the first CVD event during 2007-2017 and the following components: aortic aneurysm, cerebrovascular accidents, heart failure, myocardial infarction, peripheral vascular disease and other CVD-related conditions. Flexible parametric survival models were used to estimate ethnicity-specific adjusted hazard ratios.

RESULTS

A total of 734,543 people with and without type 2 diabetes mellitus (29,847; 4.1%) were included; most were of white ethnicity (93.0% with and 92.3% without type 2 diabetes mellitus) followed by South Asian (3.2 and 4.6%). During a median follow-up period of 11.0 years, 67,218 events occurred (6,156 in individuals with type 2 diabetes mellitus). Type 2 diabetes mellitus was associated with a small increase in CVD events (adjusted hazard ratio 1.06, 95% confidence interval 1.02-1.09) in individuals of white ethnicity; whereas the adjusted hazard ratios were considerably higher in individuals of South Asian ethnicity (1.28, 95% confidence interval 1.09-1.51), primarily due to an increased risk of myocardial infarction (1.53, 95% confidence interval 1.08-2.18).

CONCLUSIONS

Despite universal access to healthcare, there are large disparities in CVD outcomes in people with and without type 2 diabetes mellitus. Other non-traditional risk factors might play a role in the higher CVD risk associated with type 2 diabetes mellitus in individuals of South Asian ethnicity.

New-user and prevalent-user designs and the definition of study time origin in pharmacoepidemiology: A review of reporting practices

BACKGROUND

Guidance reports for observational comparative effectiveness and drug safety research recommend implementing a new-user design whenever possible, since it reduces the risk of selection bias in exposure effect estimation compared to a prevalent-user design. The uptake of this guidance has not been studied extensively.

METHODS

We reviewed 89 observational effectiveness and safety cohort studies published in six pharmacoepidemiological journals in 2018 and 2019. We developed an extraction tool to assess how frequently new-user and prevalent-user designs were reported to be implemented. For studies that implemented a new-user design in both treatment arms, we extracted information about the extent to which the moment of meeting eligibility criteria, treatment initiation, and start of follow-up were reported to be aligned.

RESULTS

Of the 89 studies included, 40% reported implementing a new-user design for both the study exposure arm and the comparator arm, while 13% reported implementing a prevalent-user design in both arms. The moment of meeting eligibility criteria, treatment initiation, and start of follow-up were reported to be aligned in both treatment arms in 53% of studies that reported implementing a new-user design. We provided examples of studies that minimized the risk of introducing bias due to unclear definition of time origin in unexposed participants, immortal time, or a time lag.

CONCLUSIONS

Almost half of the included studies reported implementing a new-user design. Implications of misalignment of study design origin were difficult to assess because it would require explicit reporting of the target estimand in original studies. We recommend that the choice for a particular study time origin is explicitly motivated to enable assessment of validity of the study.

Arguments about face masks and Covid-19 reflect broader methodologic debates within medical science

There has perhaps been no issue as contentious in Covid-19 as face masks. The most contentious scientific debate has been between those who argue that "there is no scientific evidence", by which they mean that there are no randomized controlled trials (RCTs), versus those who argue that when the evidence is considered together, "the science supports that face coverings save lives". It used to be a 'given' that to decide whether a particular factor, either exogenous or endogenous, can cause a particular disease, and in what order of magnitude, one should consider all reasonably cogent evidence. This approach is being increasingly challenged, both scientifically and politically. The scientific challenge has come from methodologic views that focus on the randomized controlled trial (RCT) as the scientific gold standard, with priority being given, either to evidence from RCTs or to observational studies which closely mimic RCTs. The political challenge has come from various interests calling for the exclusion of epidemiological evidence from consideration by regulatory and advisory committees.

Atopic eczema in adulthood and mortality: UK population-based cohort study, 1998-2016

Background

Atopic eczema affects up to 10% of adults and is becoming more common globally. Few studies have assessed whether atopic eczema increases the risk of death.

Objective

We aimed to determine whether adults with atopic eczema were at increased risk of death overall and by specific causes and to assess whether the risk varied by atopic eczema severity and activity.

Methods

The study was a population-based matched cohort study using UK primary care electronic health care records from the Clinical Practice Research Datalink with linked hospitalization data from Hospital Episode Statistics and mortality data from the Office for National Statistics from 1998 to 2016.

Results

A total of 526,736 patients with atopic eczema were matched to 2,567,872 individuals without atopic eczema. The median age at entry was 41.8 years, and the median follow-up time was 4.5 years. There was limited evidence of increased hazard for all-cause mortality in those with atopic eczema (hazard ratio = 1.04; 99% CI = 1.03-1.06), but there were somewhat stronger associations (8%-14% increased hazard) for deaths due to infectious, digestive, and genitourinary causes. Differences on the absolute scale were modest owing to low overall mortality rates. Mortality risk increased markedly with eczema severity and activity. For example, patients with severe atopic eczema had a 62% increased hazard (hazard ratio = 1.62; 99% CI = 1.54-1.71) for mortality compared with those without eczema, with the strongest associations for infectious, respiratory, and genitourinary causes.

Conclusion

The increased hazards for all-cause and cause-specific mortality were largely restricted to those with the most severe or predominantly active atopic eczema. Understanding the reasons for these increased hazards for mortality is an urgent priority.

Statin use and risk of joint replacement due to osteoarthritis and rheumatoid arthritis: a propensity-score matched longitudinal cohort study

OBJECTIVE

Statins are reported to have a potential benefit on progression of OA and on disease activity in RA, but existing evidence is conflicting. Our objective was to examine whether statins associate with reduction in the risk for joint replacement due to OA and RA.

METHODS

This was a propensity score-matched cohort study. Electronic health records from the UK Clinical Practice Research Datalink were used. We selected people prescribed statins and people never prescribed statins. Each statin user was matched to a non-user by age, gender, practice and propensity score for statin prescription. The main outcome measures were knee or hip joint replacement overall, and specifically because of OA or RA. The association between statins and risk of joint replacement was assessed using Cox proportional hazard regression. Statin exposure was categorized according to the potency of reducing low-density lipoprotein as low (21-28%), medium (32-38%) or high (42-55%) intensity.

RESULTS

A total of 178 467 statin users were matched with 178 467 non-users by age, gender, practice and propensity score. Overall, statin was not associated with reduced risk of knee or hip replacement (hazard ratio 0.99, 95% CI: 0.97, 1.03), unless prescribed at high strength (0.86, 0.75-0.98). The reduced risk was only observed for joint replacement due to RA (0.77, 0.63-0.94) but not OA (0.97, 0.94-1.01).

CONCLUSION

Statins at high intensity may reduce the risk of hip or knee replacement. This effect may be RA specific. Further studies to investigate mechanisms of risk reduction and the impact in people with RA are warranted.

Associations of Benzodiazepines, Z-Drugs, and Other Anxiolytics With Subsequent Dementia in Patients With Affective Disorders: A Nationwide Cohort and Nested Case-Control Study

OBJECTIVE

Benzodiazepines and Z-drugs are two of the most prescribed agents worldwide. However, because of their cognitive side effects, the question of their influence on the risk of dementia has been raised. The authors examined the association of benzodiazepines, Z-drugs, and other anxiolytics with incident dementia in patients with affective disorders.

METHODS

The authors conducted a cohort and nested case-control study of 235,465 patients over age 20 who were identified in the Danish National Patient Registry as having had a first-time hospital contact for an affective disorder between 1996 and 2015. From the Danish National Prescription Registry, information was obtained on all prescriptions for benzodiazepines, Z-drugs, and other anxiolytics, and patients were followed for incident dementia (defined by hospital discharge diagnosis or acetylcholinesterase inhibitor use). Cox proportional hazards and conditional logistic regression models were used to calculate hazard ratios and odds ratios with adjustment for sociodemographic and clinical variables.

RESULTS

A total of 75.9% (N=171,287) of patients had any use of benzodiazepines or Z-drugs, and during the median follow-up of 6.1 years (interquartile range, 2.7-11), 9,776 (4.2%) patients were diagnosed with dementia. Any use of benzodiazepines or Z-drugs showed no association with dementia after multiple adjustments in either the cohort analysis or a nested case-control design. In the cohort analysis, the number of prescriptions and the cumulated dose of benzodiazepines or Z-drugs at baseline were not associated with dementia. In the nested case-control study, where prescriptions were counted from 1995 until 2 years before the index date, there was a slightly higher odds ratio of dementia in patients with the lowest use of benzodiazepines or Z-drugs (odds ratio=1.08, 95% CI=1.01, 1.15) compared with no lifetime use. However, patients with the highest use had the lowest odds of developing dementia (odds ratio=0.83, 95% CI=0.77, 0.88).

CONCLUSIONS

This large cohort study did not reveal associations between use of benzodiazepines or Z-drugs and subsequent dementia, even when exposures were cumulated or divided into long- and short-acting drugs. Some results were compatible with a protective effect.

Beta-adrenergic receptor blockers and liver cancer mortality in a national cohort of hepatocellular carcinoma patients

Background: β-adrenergic signaling has been implicated in the pathology of hepatocellular carcinoma (HCC), but the evidence from clinical studies is limited. In this national population-based cohort study, we investigated the possible association of β-adrenergic receptor blockers and cancer-specific mortality among patients with primary HCC diagnosed in Sweden between 2006 and 2014.Methods: Patients were identified from the Swedish Cancer Register (n = 2104) and followed until 31 December 2015. We used Cox regression to evaluate the association of β-blockers dispensed within 90 days prior to cancer diagnosis, ascertained from the national Prescribed Drug Register, with liver cancer mortality identified from the Cause of Death Register, while controlling for socio-demographic factors, tumor characteristics, comorbidity, other medications and treatment procedures.Results: Over a median follow-up of 9.9 months, 1601 patients died (of whom 1309 from liver cancer). Compared with non-use, β-blocker use at cancer diagnosis [n = 714 (predominantly prevalent use, 93%)] was associated with lower liver cancer mortality [0.82 (0.72-0.94); p = .005]. Statistically significant associations were observed for non-selective [0.71 (0.55-0.91); p = .006], β1-receptor selective [0.86 [0.75-1.00); p = .049] and lipophilic [0.78 (0.67-0.90); p = .001] β-blockers. No association was observed for hydrophilic β-blockers [1.01 (0.80-1.28); p = .906] or other antihypertensive medications. Further analysis suggested that the observed lower liver cancer mortality rate was limited to patients with localized disease at diagnosis [0.82 (0.67-1.01); p = .062].Conclusion: β-blocker use was associated with lower liver cancer mortality rate in this national cohort of patients with HCC. A higher-magnitude inverse association was observed in relation to non-selective β-blocker use.

Methodological considerations when analysing and interpreting real-world data

In the absence of relevant data from randomized trials, nonexperimental studies are needed to estimate treatment effects on clinically meaningful outcomes. State-of-the-art study design is imperative for minimizing the potential for bias when using large healthcare databases (e.g. claims data, electronic health records, and product/disease registries). Critical design elements include new-users (begin follow-up at treatment initiation) reflecting hypothetical interventions and clear timelines, active-comparators (comparing treatment alternatives for the same indication), and consideration of induction and latent periods. Propensity scores can be used to balance measured covariates between treatment regimens and thus control for measured confounding. Immortal-time bias can be avoided by defining initiation of therapy and follow-up consistently between treatment groups. The aim of this manuscript is to provide a non-technical overview of study design issues and solutions and to highlight the importance of study design to minimize bias in nonexperimental studies using real-world data.

The present and future scope of real-world evidence research in diabetes: What questions can and cannot be answered and what might be possible in the future?

The last decade has witnessed an exponential growth in the opportunities to collect and link health-related data from multiple resources, including primary care, administrative, and device data. The availability of these "real-world," "big data" has fuelled also an intense methodological research into methods to handle them and extract actionable information. In medicine, the evidence generated from "real-world data" (RWD), which are not purposely collected to answer biomedical questions, is commonly termed "real-world evidence" (RWE). In this review, we focus on RWD and RWE in the area of diabetes research, highlighting their contributions in the last decade; and give some suggestions for future RWE diabetes research, by applying well-established and less-known tools to direct RWE diabetes research towards better personalized approaches to diabetes care. We underline the essential aspects to consider when using RWD and the key features limiting the translational potential of RWD in generating high-quality and applicable RWE. Only if viewed in the context of other study designs and statistical methods, with its pros and cons carefully considered, RWE will exploit its full potential as a complementary or even, in some cases, substitutive source of evidence compared to the expensive evidence obtained from randomized controlled trials.

Atopic eczema and fracture risk in adults: A population-based cohort study

BACKGROUND

Limited evidence suggests increased fracture risk in people with atopic eczema. Any link could have substantial effect; atopic eczema is common, and fractures have associated morbidity and mortality.

OBJECTIVE

We sought to examine whether atopic eczema is associated with fracture and whether fracture risk varies with eczema severity.

METHODS

We performed a matched cohort study set in primary care (Clinical Practice Research Datalink GOLD 1998-2016) and linked hospital admissions data (Hospital Episode Statistics), including adults (≥18 years old) with atopic eczema matched (by age, sex, general practice, and cohort entry date) with up to 5 individuals without eczema. We estimated hazard ratios (HRs) from stratified Cox regression comparing risk of major osteoporotic (hip, pelvis, spine, wrist, and proximal humerus) fractures individually and any fracture in those with and without atopic eczema.

RESULTS

We identified 526,808 people with atopic eczema and 2,569,030 people without atopic eczema. Those with eczema had increased risk of hip (HR, 1.10; 99% CI, 1.06-1.14), pelvic (HR, 1.10; 99% CI, 1.02-1.19), spinal (HR, 1.18; 99% CI, 1.10-1.27), and wrist (HR, 1.07; 99% CI, 1.03,-1.11) fractures. We found no evidence of increased proximal humeral (HR, 1.06; 99% CI, 0.97-1.15) fracture risk. Fracture risk increased with increasing eczema severity, with the strongest associations in people with severe eczema (compared with those without) for spinal (HR, 2.09; 99% CI, 1.66-2.65), pelvic (HR, 1.66; 99% CI, 1.26-2.20), and hip (HR, 1.50; 99% CI, 1.30-1.74) fractures. Associations persisted after oral glucocorticoid adjustment.

CONCLUSIONS

People with atopic eczema have increased fracture risk, particularly major osteoporotic fractures.

Atopic Eczema in Adulthood and Risk of Depression and Anxiety: A Population-Based Cohort Study

BACKGROUND

Atopic eczema is a common and debilitating condition associated with depression and anxiety, but the nature of this association remains unclear.

OBJECTIVE

To explore the temporal relationship between atopic eczema and new depression/anxiety.

METHODS

This matched cohort study used routinely collected data from the UK Clinical Practice Research Datalink, linked to hospital admissions data. We identified adults with atopic eczema (1998-2016) using a validated algorithm, and up to 5 individuals without atopic eczema matched on date of diagnosis, age, sex, and general practice. We estimated the hazard ratio (HR) for new depression/anxiety using stratified Cox regression to account for age, sex, calendar period, Index of Multiple Deprivation, glucocorticoid treatment, obesity, smoking, and harmful alcohol use.

RESULTS

We identified 526,808 adults with atopic eczema who were matched to 2,569,030 without. Atopic eczema was associated with increased incidence of new depression (HR, 1.14; 99% CI, 1.12-1.16) and anxiety (HR, 1.17; 99% CI, 1.14-1.19). We observed a stronger effect of atopic eczema on depression with increasing atopic eczema severity (HR [99% CI] compared with no atopic eczema: mild, 1.10 [1.08-1.13]; moderate, 1.19 [1.15-1.23]; and severe, 1.26 [1.17-1.37]). A dose-response association, however, was less apparent for new anxiety diagnosis (HR [99% CI] compared with no atopic eczema: mild, 1.14 [1.11-1.18]; moderate, 1.21 [1.17-1.26]; and severe, 1.15; [1.05-1.25]).

CONCLUSIONS

Adults with atopic eczema are more likely to develop new depression and anxiety. For depression, we observed a dose-response relationship with atopic eczema severity.

Statin Use Over 65 Years of Age and All-Cause Mortality: A 10-Year Follow-Up of 19 518 People

OBJECTIVES

As life expectancy continues to rise, the burden of cardiovascular disease among older people is expected to increase, making cardiovascular prevention in older people an issue of growing interest and public health importance. We aimed to explore the long-term effects of adherence to statins on mortality and cardiovascular morbidity among older adults.

DESIGN

A historical population-based cohort study using routinely collected data.

SETTING

Clalit Health Services Northern District.

PARTICIPANTS

We followed members of Clalit Health Services aged 65 years or older who were eligible for primary cardiovascular prevention for a period of 10 years.

MEASUREMENTS

We fitted Cox regression models to assess the association between the adherence to statin therapy and all-cause mortality and cardiovascular morbidity, adjusting for cardiovascular risk factors and associated morbidity as time-updated variables.

RESULTS

The analysis included 19 518 older adults followed during 10 years (median = 9.7 y). All-cause mortality rates were 34% lower among those who had adhered to statin treatment, compared with those who had not (hazard ratio [HR] = .66; 95% confidence interval [CI] = .56-.79). Adherence to statins was also associated with fewer atherosclerotic cardiovascular disease events (HR = .80; 95% CI = .71-.81). The benefit of statin use did not diminish among beyond age 75 and was evident for both women and men.

CONCLUSION

Adherence to statins may be associated with reduced mortality and cardiovascular morbidity among older adults, regardless of age and sex. J Am Geriatr Soc 67:2038-2044, 2019.

History of Benzodiazepine Prescriptions and Risk of Dementia: Possible Bias Due to Prevalent Users and Covariate Measurement Timing in a Nested Case-Control Study

Previous estimates of whether long-term exposure to benzodiazepines increases dementia risk are conflicting and are compromised by the difficulty of controlling for confounders and by reverse causation. We investigated how estimates for the association between benzodiazepine use and later dementia incidence varied based on study design choices, using a case-control study nested within the United Kingdom's Clinical Practice Research Datalink. A total of 40,770 dementia cases diagnosed between April 2006 and July 2015 were matched on age, sex, available data history, and deprivation to 283,933 control subjects. Benzodiazepines and Z-drug prescriptions were ascertained in a drug-exposure period 4-20 years before dementia diagnosis. Estimates varied with the inclusion of new or prevalent users, with the timing of covariate ascertainment, and with varying time between exposure and outcome. There was no association between any new prescription of benzodiazepines and dementia (adjusted odds ratio (OR) = 1.03, 95% confidence interval (CI): 1.00, 1.07), whereas an inverse association was observed among prevalent users (adjusted OR = 0.91, 95% CI: 0.87, 0.95), although this was likely induced by unintentional adjustment for colliders. By considering the choice of confounders and timing of exposure and covariate measurement, our findings overall are consistent with no causal effect of benzodiazepines or Z-drugs on dementia incidence.

Re-evaluating Safety and Effectiveness of Dabigatran Versus Warfarin in a Nationwide Data Environment: A Prevalent New-User Design Study

Introduction

The new user cohort design is widely used to assess the effects of a new drug, such as dabigatran, but inherently excludes some users due to prior use of the comparator drug, for example warfarin. The prevalent new-user design offers a solution that includes all eligible users of the new drug.

Objective

To evaluate the safety and effectiveness of dabigatran versus warfarin in non-valvular atrial fibrillation (NVAF) patients with prevalent new-user design.

Methods

Taiwan National Health Insurance and mortality data from 2011 through 2015 were utilized. From an incident NVAF cohort, we identified dabigatran initiators as either incident or prevalent (switchers from warfarin) new users. Time- and prescription-based exposure sets were formed for dabigatran initiators to account for prior warfarin prescriptions. A comparable warfarin user was matched on the time-conditional propensity score to the dabigatran initiator in each set. The matched patients were followed for clinical outcomes, with Cox proportional hazards model used to estimate hazard ratios (HRs).

Results

There were 10,811 dabigatran initiators, including 22% prevalent new users (switchers), who formed the exposure sets and were matched 1:1 to warfarin users. Dabigatran use was associated with lower risks of intracranial hemorrhage (HR 0.51; 95% confidence interval [CI] 0.39, 0.66) and gastrointestinal bleeding (HR 0.81; 95% CI 0.70, 0.92), compared with warfarin use. These effects were similar between the incident and prevalent new users.

Conclusion

Using a design that includes both incident and prevalent new users of dabigatran, the use of dabigatran is associated with lower major bleeding risk than warfarin use among patients with incident NVAF.

Electronic supplementary material

The online version of this article (10.1007/s40801-019-0156-2) contains supplementary material, which is available to authorized users.

Selection bias introduced by informative censoring in studies examining effects of vaccination in infancy

Background

Many studies have examined ‘non-specific’ vaccine effects on infant mortality: attention has been particularly drawn to diphtheria-tetanus-pertussis (DTP) vaccine, which has been proposed to be associated with an increased mortality risk. Both right and left censoring are common in such studies.

Methods

We conducted simulation studies examining right censoring (at measles vaccination) and left censoring (by excluding early follow-up) in a variety of scenarios in which confounding was and was not present. We estimated both unadjusted and adjusted hazard ratios (HRs), averaged across simulations.

Results

We identified scenarios in which right-censoring at measles vaccination was informative and so introduced bias in the direction of a detrimental effect of DTP vaccine. In some, but not all, situations, adjusting for confounding by health status removed the bias caused by censoring. However, such adjustment will not always remove bias due to informative censoring: inverse probability weighting was required in one scenario. Bias due to left censoring arose when both health status and DTP vaccination were associated with mortality during the censored early follow-up and was in the direction of attenuating a beneficial effect of DTP on mortality. Such bias was more severe when the effect of DTP changed over time.

Conclusions

Estimates of non-specific effects of vaccines may be biased by informative right or left censoring. Authors of studies estimating such effects should consider the potential for such bias and use appropriate statistical approaches to control for it. Such approaches require measurement of prognostic factors that predict censoring.

Long-term airborne dioxin exposure and breast cancer risk in a case-control study nested within the French E3N prospective cohort

BACKGROUND

Dioxins, Group 1 carcinogens, are emitted by industrial chlorinated combustion processes and suspected to increase breast cancer risk through receptor-mediated pathways.

OBJECTIVES

We estimated breast cancer risk associated with airborne dioxin exposure, using geographic information system (GIS) methods and historical exposure data.

METHODS

We designed a case-control study (429 breast cancer cases diagnosed between 1990 and 2008, matched to 716 controls) nested within the E3N (Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale) cohort. Airborne dioxin exposure was assessed using a GIS-based metric including participants' residential history, technical characteristics of 222 dioxin sources, residential proximity to dioxin sources, exposure duration and wind direction. Odds ratios (OR) and 95% confidence intervals (CI) associated with quintiles of cumulative exposure were estimated using multivariate logistic regression models.

RESULTS

We observed no increased risk of breast cancer for higher dioxin exposure levels overall and according to hormone-receptor status. We however observed a statistically significant OR for Q2 versus Q1 overall (1.612, 95% CI: 1.042-2.493) and for estrogen-receptor (ER) positive breast cancer (1.843, 95% CI: 1.033-3.292).

CONCLUSIONS

Overall, as well as according to hormone-receptor status, no increased risk was observed for higher airborne dioxin exposure. The increased risk for low exposure levels might be compatible with non-monotonic dose-response relationship. Confirmation of our findings is required. Our GIS-based metric may provide an alternative in absence of ambient dioxin monitoring and may allow assessing exposure to other pollutants.

Observational studies of treatment effectiveness: worthwhile or worthless?

Observational studies which evaluate effectiveness are often viewed with skepticism owing to the fact that patients are not randomized to treatment, meaning that results are more prone to bias. Therefore, randomized controlled trials remain the gold standard for evaluating treatment effectiveness. However, it is not always possible to conduct randomized trials. This may be due to financial constraints, for example, in identifying funding for a randomized trial for medicines that have already gained market authorization. There can also be challenges with recruitment, for example, of people with rare conditions or in hard-to-reach population subgroups. This is why observational studies are still needed. In this manuscript, we discuss how researchers can mitigate the risk of bias in the most common type of observational study design for evaluation of treatment effectiveness, the cohort study. We outline some key issues that warrant careful consideration at the outset when the question is being developed and the cohort study is being designed. We focus our discussion on the importance of deciding when to start follow-up in a study, choosing a comparator, managing confounding and measuring outcomes. We also illustrate the application of these considerations in a more detailed case study based on an examination of comparative effectiveness of two antidiabetic treatments using data collected during routine clinical practice.

A review of time scale fundamentals in the g-formula and insidious selection bias

PURPOSE OF REVIEW

We review recent examples of data analysis with the g-formula, a powerful tool for analyzing longitudinal data and survival analysis. Specifically, we focus on the common choices of time scale and review inferential issues that may arise.

RECENT FINDINGS

Researchers are increasingly engaged with questions that require time scales subject to left-truncation and right-censoring. The assumptions necessary for allowing right-censoring are well defined in the literature, whereas similar assumptions for left-truncation are not well defined. Policy and biologic considerations sometimes dictate that observational data must be analyzed on time scales that are subject to left-truncation, such as age.

SUMMARY

Further consideration of left-truncation is needed, especially when biologic or policy considerations dictate that age is the relevant time scale of interest. Methodologic development is needed to reduce potential for bias when left-truncation may occur.

Severe and predominantly active atopic eczema in adulthood and long term risk of cardiovascular disease: population based cohort study

OBJECTIVE

To investigate whether adults with atopic eczema are at an increased risk of cardiovascular disease and whether the risk varies by atopic eczema severity and condition activity over time.

DESIGN

Population based matched cohort study.

SETTING

UK electronic health records from the Clinical Practice Research Datalink, Hospital Episode Statistics, and data from the Office for National Statistics, 1998-2015.

PARTICIPANTS

Adults with a diagnosis of atopic eczema, matched (on age, sex, general practice, and calendar time) to up to five patients without atopic eczema.

MAIN OUTCOME MEASURES

Cardiovascular outcomes (myocardial infarction, unstable angina, heart failure, atrial fibrillation, stroke, and cardiovascular death).

RESULTS

387 439 patients with atopic eczema were matched to 1 528 477 patients without atopic eczema. The median age was 43 at cohort entry and 66% were female. Median follow-up was 5.1 years. Evidence of a 10% to 20% increased hazard for the non-fatal primary outcomes for patients with atopic eczema was found by using Cox regression stratified by matched set. There was a strong dose-response relation with severity of atopic eczema. Patients with severe atopic eczema had a 20% increase in the risk of stroke (hazard ratio 1.22, 99% confidence interval 1.01 to 1.48), 40% to 50% increase in the risk of myocardial infarction, unstable angina, atrial fibrillation, and cardiovascular death, and 70% increase in the risk of heart failure (hazard ratio 1.69, 99% confidence interval 1.38 to 2.06). Patients with the most active atopic eczema (active >50% of follow-up) were also at a greater risk of cardiovascular outcomes. Additional adjustment for cardiovascular risk factors as potential mediators partially attenuated the point estimates, though associations persisted for severe atopic eczema.

CONCLUSIONS

Severe and predominantly active atopic eczema are associated with an increased risk of cardiovascular outcomes. Targeting cardiovascular disease prevention strategies among these patients should be considered.

Pharmacoepidemiology in Pharmacogenetics

Epidemiologic methods provide rigorous means by which to study the interplay between genetic factors and drug response. In this chapter, we describe the differences between experimental and observational study designs, and illustrate how to implement the highly efficient case-control study design. We discuss analytic approaches to evaluating gene-drug interactions within typical study designs and review sources of bias that must be assessed and accounted for in epidemiologic analyses.

Causality and causal inference in epidemiology: the need for a pluralistic approach

Causal inference based on a restricted version of the potential outcomes approach reasoning is assuming an increasingly prominent place in the teaching and practice of epidemiology. The proposed concepts and methods are useful for particular problems, but it would be of concern if the theory and practice of the complete field of epidemiology were to become restricted to this single approach to causal inference. Our concerns are that this theory restricts the questions that epidemiologists may ask and the study designs that they may consider. It also restricts the evidence that may be considered acceptable to assess causality, and thereby the evidence that may be considered acceptable for scientific and public health decision making. These restrictions are based on a particular conceptual framework for thinking about causality. In Section 1, we describe the characteristics of the restricted potential outcomes approach (RPOA) and show that there is a methodological movement which advocates these principles, not just for solving particular problems, but as ideals for which epidemiology as a whole should strive. In Section 2, we seek to show that the limitation of epidemiology to one particular view of the nature of causality is problematic. In Section 3, we argue that the RPOA is also problematic with regard to the assessment of causality. We argue that it threatens to restrict study design choice, to wrongly discredit the results of types of observational studies that have been very useful in the past and to damage the teaching of epidemiological reasoning. Finally, in Section 4 we set out what we regard as a more reasonable ‘working hypothesis’ as to the nature of causality and its assessment: pragmatic pluralism.

Conditioning on future exposure to define study cohorts can induce bias: the case of low-dose acetylsalicylic acid and risk of major bleeding

Background

A principle of cohort studies is that cohort membership is defined by current rather than future exposure information. Pharmacoepidemiologic studies using existing databases are vulnerable to violation of this principle. We evaluated the impact of using data on future redemption of prescriptions to determine cohort membership, motivated by a published example seeking to emulate a “per-protocol” association between continuous versus never use of low-dose acetylsalicylic acid (ASA) and major bleeding (e.g., cerebral hemorrhage or gastrointestinal bleeding).

Materials and methods

Danish medical registry data from 2004 to 2011 were used to construct two analytic cohorts. In Cohort 1, we used information about future redemption of low-dose ASA prescriptions to identify cohorts of continuous and never-ASA users. In Cohort 2, we identified ASA initiators and non-initiators using only contemporaneous data and censored follow-up for changes in use over time. We implemented propensity score-matched Poisson regression to evaluate associations between ASA use and major bleeding and estimated adjusted incidence rate differences (IRDs) per 1,000 person-years and ratios (IRRs) overall and stratified by time since initiation.

Results

Among >6 million eligible Danish adults, we identified 403,693 low-dose ASA initiators (Cohort 2), of whom 189,150 were defined as continuous users (Cohort 1). Overall, IRDs and IRRs were similar across cohorts. However, the IRD for major bleeding in the first 90 days was substantially larger in Cohort 1 (IRD=25 per 1,000 person-years) compared with Cohort 2 (IRD=10 per 1,000 person-years).

Conclusion

Using future medication redemption data to define baseline cohorts violates basic epidemiologic principles. Compared with an approach using only contemporaneous data to define cohorts, the approach based on future redemption data generated a substantially higher short-term association between low-dose ASA use and major bleeding on the absolute, but not the relative, scale possibly due to selection and immortal time biases.

Mortality gap for people with bipolar disorder and schizophrenia: UK-based cohort study 2000-2014

BackgroundBipolar disorder and schizophrenia are associated with increased mortality relative to the general population. There is an international emphasis on decreasing this excess mortality.AimsTo determine whether the mortality gap between individuals with bipolar disorder and schizophrenia and the general population has decreased.MethodA nationally representative cohort study using primary care electronic health records from 2000 to 2014, comparing all patients diagnosed with bipolar disorder or schizophrenia and the general population. The primary outcome was all-cause mortality.ResultsIndividuals with bipolar disorder and schizophrenia had elevated mortality (adjusted hazard ratio (HR) = 1.79, 95% CI 1.67-1.88 and 2.08, 95% CI 1.98-2.19 respectively). Adjusted HRs for bipolar disorder increased by 0.14/year (95% CI 0.10-0.19) from 2006 to 2014. The adjusted HRs for schizophrenia increased gradually from 2004 to 2010 (0.11/year, 95% CI 0.04-0.17) and rapidly after 2010 (0.34/year, 95% CI 0.18-0.49).ConclusionsThe mortality gap between individuals with bipolar disorder and schizophrenia, and the general population is widening.

Statin use and risk of recurrent venous thrombosis: results from the MEGA follow-up study

INTRODUCTION

Whether statin use after first venous thrombosis reduces the risk of recurrence is uncertain. Therefore, we aimed to examine the risk of recurrent venous thrombosis in statin users vs non-users.

METHODS

Patients with a first venous thrombosis were recruited from the MEGA follow-up study. Information on statin use was obtained by linkage to the Dutch Foundation for Pharmaceutical Statistics register. Linkage was successful in 54% of all patients (n = 2,547). Cox-regression models with statin-exposure as a time-dependent co-variate were used to estimate hazard ratios (HR) with 95% confidence intervals (CI 95) for recurrence.

RESULTS

Statin therapy was continued in 153 (6.0%) patients and initiated in 233 (9.1%) patients during a median follow-up of 5.7 years. There were 367 recurrent venous thrombotic events, of which 32 occurred among statin users. Incident statin use was associated with 22% reduced risk of recurrence after multivariable adjustments (HR 0.78, CI 95: 0.46-1.31), and 13% reduced risk after propensity score adjustment (HR 0.87, CI 95: 0.52-1.47). Statin use seemed not to have an effect on recurrence in patients with an unprovoked first event (multivariable HR 1.03, CI 95: 0.54-1.98), but the statistical power was low due to few events and the results must be interpreted with caution. In general, the risk estimates were slightly attenuated when prevalent users were included in the analyses.

CONCLUSION

Our findings suggest that statins may have a modest decreasing effect on the risk of recurrent venous thrombosis. While we took care to minimize bias and confounding, the causality of the association is still unsettled.

What's in a Name? The Incorrect Use of Case Series as a Study Design Label in Studies Involving Dogs and Cats

BACKGROUND

Study design labels are used to identify relevant literature to address specific clinical and research questions and to aid in evaluating the evidentiary value of research. Evidence from the human healthcare literature indicates that the label "case series" may be used inconsistently and inappropriately.

OBJECTIVE

Our primary objective was to determine the proportion of studies in the canine and feline veterinary literature labeled as case series that actually corresponded to descriptive cohort studies, population-based cohort studies, or other study designs. Our secondary objective was to identify the proportion of case series in which potentially inappropriate inferential statements were made.

DESIGN

Descriptive evaluation of published literature.

PARTICIPANTS

One-hundred published studies (from 19 journals) labeled as case series.

METHODS

Studies were identified by a structured literature search, with random selection of 100 studies from the relevant citations. Two reviewers independently characterized each study, with disagreements resolved by consensus.

RESULTS

Of the 100 studies, 16 were case series. The remaining studies were descriptive cohort studies (35), population-based cohort studies (36), or other observational or experimental study designs (13). Almost half (48.8%) of the case series or descriptive cohort studies, with no control group and no formal statistical analysis, included inferential statements about the efficacy of treatment or statistical significance of potential risk factors.

CONCLUSIONS

Authors, peer-reviewers, and editors should carefully consider the design elements of a study to accurately identify and label the study design. Doing so will facilitate an understanding of the evidentiary value of the results.

Methodologic Issues When Estimating Risks in Pharmacoepidemiology

Risk is an important parameter to describe the occurrence of health outcomes over time. However, many outcomes of interest in healthcare settings, such as disease incidence, treatment initiation, and cause-specific mortality, may be precluded from occurring by other events, often referred to as competing events. Here, we review straightforward approaches to estimate risk in the presence of competing events. We illustrate the application of these methods using timely examples in pharmacoepidemiologic research and compare results to those obtained using analytic simplifications commonly used to handle competing events. These examples demonstrate how the analytic methods used to account for competing events affect the interpretation of results from pharmacoepidemiologic studies.

Prevalent new-user cohort designs for comparative drug effect studies by time-conditional propensity scores

PURPOSE

Studies of the real-world comparative effectiveness of drugs conducted using computerized healthcare databases typically involve an incident new-user cohort design for head-to-head comparisons between two medications, using exclusively treatment-naïve patients. However, the desired contrast often involves one new drug compared with an older drug, of which many users of the new drug may have switched from, seriously restricting the scope of incident new-user studies.

METHODS

We introduce prevalent new-user cohort designs for head-to-head comparative drug effect studies, where incident new users are scarce. We define time-based and prescription-based exposure sets to compute time-conditional propensity scores of initiating the newer drug and to identify matched subjects receiving the comparator drug. We illustrate this approach using data from the UK's Clinical Practice Research Datalink to evaluate whether the newer glucagon-like peptide-1 receptor agonists (GLP-1 analogs) used to treat type 2 diabetes increase the risk of heart failure, in comparison with the older similarly indicated sulfonylureas.

RESULTS

Of the 170 031 users of antidiabetic agents from 2000 onwards, 79 682 used sulfonylureas (first use 2000), while 6196 used GLP-1 analogs (first use 2007), 75% of which had previously used a sulfonylurea. After matching each GLP-1 analog user to a sulfonylurea user on the time-conditional propensity scores from prescription-based exposure sets, the hazard ratio of heart failure with GLP-1 use was 0.73 (95%CI: 0.57-0.93).

CONCLUSION

The proposed prevalent new-user cohort design for comparative drug effects studies allows the use of all or most patients exposed to the newer drug, thus permitting a more comprehensive assessment of a new drug's safety. Copyright © 2016 John Wiley & Sons, Ltd.

Counterpoint: epidemiology to guide decision-making: moving away from practice-free research

Analyses of observational data aimed at supporting decision-making are ideally framed as a contrast between well-defined treatment strategies. These analyses compare individuals' outcomes from the start of the treatment strategies under consideration. Exceptions to this synchronizing of the start of follow-up and the treatment strategies may be justified on a case-by-case basis.

Counterpoint: the treatment decision design

The comparative new-user design is a principled approach to learning about the relative risks and benefits of starting different treatments in patients who have no history of use of the treatments being studied. Vandenbroucke and Pearce (Am J Epidemiol. 2015;182(10):826-833) discuss some problems inherent in incident exposure designs and argue that epidemiology may be harmed by a rigid requirement that follow-up can only begin at first exposure. In the present counterpoint article, a range of problems in pharmacoepidemiology that do not necessarily require that observation begin at first exposure are discussed. For example, among patients who are past or current users of a medication, we might want to know whether treatment should be augmented, switched, restarted, or discontinued. To answer these questions, a generalization of the new-user design, the treatment decision design, which identifies cohorts anchored at times when treatment decisions are being made, such as the evaluation of laboratory parameters, is discussed. The design aims to provide estimates that are directly relevant to physicians and patients, helping them to better understand the risks and benefits of the different treatment choices that they are considering.