Space-Time-Stratified Case-Crossover Design in Environmental Epidemiology Study

PurposeTo determine the association between the number of flares systemic lupus erythematosus (SLE) patients experience and damage accrual, independently of other known risk factors.MethodsSLE patients (34 centres, nine Latin American countries) with a recent diagnosis (≤2 years) and ≥3 evaluations were studied. Disease activity was ascertained with the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and damage with the SLICC/ACR Damage Index (SDI). Flare was defined as an increase ≥4 points in the SLEDAI between two study visits. An ambidirectional case- crossover design was used to determine the association between the number of flares and damage accrual.Results901 patients were eligible for the study; 500 of them (55.5%) experienced at least one flare, being the mean number of flares 0.9 (SD: 1.0). 574 intervals from 251 patients were included in the case-crossover design since they have case and control intervals, whereas, the remaining patients did not. Their mean age at diagnosis was 27.9 years (SD: 11.1), 213 (84.9%) were women. The mean baseline SDI and SLEDAI were 1.3 (1.3) and 13.6 (8.1), respectively. Other features were comparable to those of the entire sample. After adjusting for possible confounding variables, the number of flares, regardless of their severity, was associated with damage accrual (SDI) OR 2.05, 95% CI 1.43 to 2.94, p<0.001 (OR 2.62, 95% CI 1.31 to 5.24, p=0.006 for severe and OR 1.91, 95% CI 1.28 to 2.83, p=0.001for mild-moderate).ConclusionsThe number of flares patients experience, regardless of their severity, increases the risk of damage accrual, independently of other known risk factors.

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Risk of Infective Endocarditis After Invasive Dental Treatments

Circulation ◽

10.1161/circulationaha.117.033131 ◽

2018 ◽

Vol 138 (4) ◽

pp. 356-363 ◽

Cited By ~ 5

Author(s):

Tzu-Ting Chen ◽

Yi-Chun Yeh ◽

Kuo-Liong Chien ◽

Mei-Shu Lai ◽

Yu-Kang Tu

Keyword(s):

Infective Endocarditis ◽

Confidence Interval ◽

Regression Model ◽

Conditional Logistic Regression ◽

Case Series ◽

Crossover Design ◽

The Self ◽

Series Design ◽

Case Crossover ◽

Study Designs

Background: Invasive dental treatments (IDTs) can yield temporary bacteremia and have therefore been considered a potential risk factor of infective endocarditis (IE). It is hypothesized that, through the trauma caused by IDTs, bacteria gain entry to the bloodstream and may attach to abnormal heart valves or damaged heart tissue, giving rise to IE. However, the association between IDTs and IE remains controversial. The aim of this study is to estimate the association between IDTs and IE. Methods: The data in this study were obtained from the Health Insurance Database in Taiwan. We selected 2 case-only study designs, case-crossover and self-controlled case series, to analyze the data. The advantage of these methods is that confounding factors that do not vary with time are adjusted for implicitly. In the case-crossover design, a conditional logistic regression model with exposure to IDTs was used to estimate the risks of IE following an IDT with 4, 8, 12, and 16 weeks delay, respectively. In the self-controlled case series design, a conditional Poisson regression model was used to estimate the risk of IE for the risk periods of 1 to 4, 5 to 8, 9 to 12, and 13 to 16 weeks following an IDT. Results: In total, 9120 and 8181 patients with IE were included in case-crossover design and self-controlled case series design, respectively. In the case-crossover design, 277 cases and 249 controls received IDTs during the exposure period, and the odds ratio was 1.12 (95% confidence interval, 0.94–1.34) for 4 weeks. In the self-controlled case series design, we observed that 407 IEs occurred during the first 4 weeks after IDTs, and the age-adjusted incidence rate ratio was 1.14 (95% confidence interval, 1.02–1.26) for 1 to 4 weeks after IDTs. Conclusions: In both study designs, we did not observe a clinically larger risk for IE in the short periods after IDTs. We also found no association between IDTs and IE among patients with a high risk of IE. Therefore, antibiotic prophylaxis for the prevention of IE is not required for the Taiwanese population.

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Heat and Cold-related Hospitalization Risk in North-East of Iran: A Time-stratified Case Crossover Design

10.21203/rs.3.rs-513713/v1 ◽

2021 ◽

Author(s):

Omid Aboubakri ◽

Hamid Reza Shoraka ◽

Joan Ballester ◽

Rahim Sharafkhani

Keyword(s):

Linear Model ◽

Hospital Admissions ◽

Extreme Values ◽

Crossover Design ◽

Preventive Program ◽

North East ◽

Distributed Lag ◽

Case Crossover ◽

Non Linear ◽

The Impact

Abstract Background: This study aimed to estimate hospitalization risk/number attributed to air extreme temperatures using time-stratified case crossover study and distributed lag non-linear model in a region of Iran during 2015-2019.Methods: A time-stratified case crossover design based on aggregated exposure data was used in this study. In order to have no overlap bias in the estimations, a fixed and disjointed window by using one-month strata was used in the design. A conditional Poisson regression model allowing for over dispersion (Quasi-Poisson) was applied into Distributed Lag Non-linear Model (DLNM). Different approaches were applied to estimate Optimum Temperature (OT). In the model, the interaction effect between temperature and humidity was assessed to see if the impact of heat or cold on Hospital Admissions (HAs) are different between different levels of humidity.Results: The cumulative effect of heat during 21 days was not significant and it was the cold that had significant cumulative adverse effect on all groups. While the number of HAs attributed to any ranges of heat, including medium, high, extreme and even all values were negligible, but a large number was attributable to cold values; about 10000 HAs were attributable to all values of cold temperature, of which about 9000 were attributed to medium range and about 1000 and less than 500 were attributed to high and extreme values of cold, respectively.Conclusion: This study highlights the need for interventions in cold seasons by policymakers. The results inform researchers as well as policy makers to address both men and women and elderly when any plan or preventive program is developed in the area under study.

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