A case-crossover design to assess case and control periods was employed. Should we use a case-crossover design? Lesson 15: Crossover Designs. A Case- Crossover Study of Sleep and Childhood Injury . To evaluate the association between sleep and wakefulness duration and childhood unintentional injury. Study Design. Case- crossover study. Methods. Two hundred ninety- two injured children who presented at the Children's Emergency Center of Udine, Italy, or their parents were interviewed after a structured questionnaire. Information was collected concerning sociodemographic variables, participant's habits, and injury characteristics, including a brief description of the accident dynamics. ![]() Sleep or wakefulness status of the child was assessed retrospectively for each of the 4. For each child, we compared the 2. Nonparametric tests were conducted to compare the difference of sleep duration between case and control periods. In addition, we conducted intrapersonal conditional logistic regression analyses and estimated relative risks (RRs) and 9. CIs). Results. Overall, more children had longer hours of sleep during the control period than during the case period. However, this difference was significant for boys only. A direct association between injury risk and sleeping < 1. RR: 2. 3. 3; 9. 5% CI: 1. RR: 1. 0. 0; 9. 5% CI: . This association was particularly strong among boys attending nursery school. We also found a direct association between injury occurring between 4 pm and midnight, and being awake for at least 8 hours before injury occurred (both sexes, RR: 4. CI: 1. 1. 3–1. 4. Conclusions. Our findings show that inadequate sleep duration and lack of daytime naps are transient exposures that may increase the risk of injury among children. Case-crossover designs for alcohol use. Schwartz J Selection bias and confounding in case-crossover analyses of environmental time-series.These results suggest new prospects for injury prevention in childhood. Among infants, injury represented only 2% of overall mortality, whereas in the 2 older age groups injuries accounted for 1. Mortality, however, is just the tip of a pyramid, where for each injury resulting in a death there are many injuries causing hospitalization and treatment in emergency centers, by general practitioners or by paramedics only. Sudden events are often caused by complex, concatenated mechanisms whose identification may fail because they are transient in nature. In particular, traditional case–control studies may not be well suited to investigate relevant risk factors for sudden events. ![]() QS Primer: Case-Crossover Design. Should we use a case-crossover design. I., et al., Heat-related mortality in dairy cattle. A crossover design is a repeated measurements design such. In medical clinical trials the disease should be chronic. Use the following terms. Stress as a Trigger for Relapses in IBD. Should we use a case-crossover design? Annu Rev Public Health. Case-crossover studies of occupational trauma: methodological. Should we use a case-crossover design? The case-crossover design has further been used to evaluate a wide range of. Should we use a case-crossover design? Annu Rev Public Health. ![]() The case- crossover design, in contrast, has proved to be particularly useful when investigating how transient exposures can trigger acute events, such as cardiovascular events,5,6injuries,7–1. The case- crossover design has also been proposed as a useful method in the study of occupational injuries. This epidemiologic method has been successfully applied to evaluate the risk of childhood injuries associated with traffic volume and speed on the roads crossed by young pedestrians. The case- crossover design offers a number of advantages. Cases serve as their own controls and a participant's exposure at the time of the event of interest (case period) is compared with another period when the participant was not a case (control period). Therefore, it is not required to sample additional control participants. In the analysis, each participant is considered a stratum in a case–control study, where cases and controls are times. Comparisons are made within each participant; therefore, this approach controls by design for potential confounding caused by age, sex, personality, and other stable participant- specific covariates. Because there is evidence that among adults sleepiness may be a factor and a cofactor of vehicle accidents. METHODSData Collection. This study was conducted at the children's emergency room of the pediatrics department (CERP) of the University of Udine, the only acute pediatric care center in the Province of Udine. Only a few children present to the general emergency room instead of CERP, and the most plausible reasons are being borderline- aged or having suffered a life- threatening injury requiring transportation to the hospital by ambulance or helicopter. We trained 5 interviewers (2 medical doctors, 2 medical students, and 1 biologist working in the medical field) who staffed CERP between May 1. July 4, 1. 99. 9, for a total of 2. Seven- hour shifts were from 9 am to 4pm, 8- hour shifts from 4 pm to midnight. Shifts were assigned so that each day of the week was covered 8 times (4 seven- hour and 4 eight- hour shifts), but with no more than 1 shift a day. The interviewer on duty approached patients with acute injury presenting to CERP. We decided to enroll patients who declared unintentional injuries, who were treated and discharged from the emergency department or admitted to any of the hospital services, and who were accompanied by at least 1 parent giving written informed consent. After a structured questionnaire, the interviewers conducted in person interviews with the patient's mother or father or with the child, if the child was old enough to understand and properly answer the questions. The interviews took place while waiting for the pediatrician to see the injured child or immediately after the visit. Complete interviews lasted . Information collected concerned characteristics of the patient, such as sex; age and educational level; acute or chronic use of medication; the child's usual sleeping pattern; the child's sleeping pattern during the last week; date, hour, and characteristics of injury; and a short narrative reconstruction of the accident. The interviewers also investigated the 4. International Classification of Diseases, Ninth Revision E- codes were assigned to each injury by one medical doctor (F. V.) after reading the description of the injury dynamics. Statistical Analysis. This was a case- crossover study, in which each participant acted as his or her own control. We compared sleep and wakefulness duration in the 2. The dependent variable was the presence or absence of injury. The exposure categories were obtained dichotomizing daily sleep amount and length of wakefulness periods. Conditional logistic regression was used to estimate relative risks (RRs) and 9. CIs). First, we calculated the RR of injury during a 2. Second, for injuries occurring between 4 pm and midnight, we calculated the RR for having been awake for at least 8 hours, compared with < 8 hours. These cutoffs were chosen according to the methodology developed by Maclure. In brief, we repeated the risk calculations varying the time intervals and chose the cutoffs that maximized the RR. Our selection was also supported by biological reasons. In fact, 1. 0 hours were also the median and the mean duration of sleep in our sample. For sleep duration, we considered as the effect period the whole day, from rising to going to bed, because we assumed that influence exerted by insufficient sleep started immediately after rising in the morning and lasted until going to bed in the evening. Both nighttime sleep and daytime naps were included when considering as exposure a sleep duration < 1. In fact, Kaplan et al. In addition, children's sleep distribution has been shown to depend on age. Separate analyses were also conducted using the sleep duration variable as continuous rather than dichotomous. This approach allowed for an evaluation of a possible dose–response relation between duration of sleep and childhood injury. Finally, we evaluated differences between usual sleep duration and sleep duration during the 4. In the analyses regarding wakefulness duration, we chose 8 hours as a cutoff because it is likely that if a child had been awake for such a period, no naps were taken early in the afternoon. For wakefulness duration, we selected as the effect period the part of the day starting from 4 pm until going to bed, because it provided the highest RR estimates among all periods allowing for a previous 8- hour wakefulness. In stratified analyses, we grouped cases by age and type of school attendance, as follows: < 1 year old; 1 to 2 years old; children attending nursery school (3–5 years old); children attending elementary school (6–1. In fact, not only age may be associated with injury occurrence, injury nature, and sleep characteristics, but also school type may be an important factor in that it influences the children's habits (eg, bedtime, rise time, and leisure activities). For the case- crossover analyses, the effect measures were calculated considering all the participants, and after excluding children < 1 year of age and participants attending high school. The former group was excluded because their role was unlikely to be active in determining the injury. The latter group was excluded because many risk factors other than intrapersonal variation of sleep are likely to play a much more relevant role. In fact, these children can operate mopeds, their schools are more frequently distant from home, and they are more likely to drink alcohol. All case- crossover analyses were repeated after excluding children who were injured in circumstances that they probably could not control, that is children bitten by animals and as car passengers. Because some children could have been awake for a long time in the same day when they slept few hours overall, for injuries taking place after 4 pm, we fit a conditional logistic regression model with both sleep and wakefulness duration, to evaluate the effect of wakefulness after controlling for the other. In addition, day of the week was considered as a potential intrapersonal confounder, because it may be associated with both the risk of injury and lack of sleep. To control for potential confounding by day of the week, we included an indicator variable (weekday vs weekend) in a multivariate conditional logistic regression model. Because injury risk varies with time of day and fatigue increases with time, we evaluated possible effect modification by time of the accident. To evaluate whether the relation between sleep duration and injury varied with type of activity at the time of injury, we performed subgroup analyses according to activity risk level.
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