Marginal analysis of longitudinal count data in long sequences: Methods and applications to a driving study

Most of the available methods for longitudinal data analysis are designed and validated for the situation where the number of subjects is large and the number of observations per subject is relatively small. Motivated by the Naturalistic Teenage Driving Study (NTDS), which represents the exact opposite situation, we examine standard and propose new methodology for marginal analysis of longitudinal count data in a small number of very long sequences. We consider standard methods based on generalized estimating equations, under working independence or an appropriate correlation structure, and find them unsatisfactory for dealing with time-dependent covariates when the counts are low. For this situation, we explore a within-cluster resampling (WCR) approach that involves repeated analyses of random subsamples with a final analysis that synthesizes results across subsamples. This leads to a novel WCR method which operates on separated blocks within subjects and which performs better than all of the previously considered methods. The methods are applied to the NTDS data and evaluated in simulation experiments mimicking the NTDS.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS507 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Teenage Drivers Portable Electronic Device Use While Driving

Young drivers’ crash risk increases when they engage in certain secondary tasks while driving. Using a sample of participants from the NEXT Generation Health Study who reported having an independent driving license and driving at least one day in the last 30 days (n = 1,243), the prevalence of portable electronic device use while driving was estimated. Two measures of prevalence were calculated: (1) engaging in the behavior at least once in the last 30 days; (2) percentage of days engaged in the behavior, relative to the number of days driven in the last 30 days. A total of 82.84% reported engaging in electronic device use while driving at least once in the last 30 days. Specifically, 71.13% made or answered a phone call, 64.84% read or sent a text message, 20.29% read or sent an email, 29.11% checked a website, 71.64% changed music, 12.80% used a tablet or computer, and 52.64% looked at directions or a map. Young drivers reported using electronic devices while driving on 19.06% of the days they drove. Males were more likely to use tablet or computer while driving, teens from moderate and high affluence households were more likely to check websites, and rural participants were less likely to look at directions or a map than urban participants. The number of days participants reported driving in the last 30 days, but not self-reported miles driven, was associated with a higher likelihood of using an electronic device while driving

Hazard Perception and Distraction in Novice Drivers: Effects of 12 Months Driving Experience

The high crash risk of novice drivers has been partly attributed to their underdeveloped hazard perception abilities. Novice drivers also have an increased risk of crashes due to distractions. Studies show that novice drivers do not detect risk relevant cues and are more susceptible to distractions when compared to adult drivers. This test track study was conducted to study the effects of 12 months of driving experience on teenagers. Forty-two teenagers and their parents drove through hazard perception scenarios while engaged in secondary tasks. These participants had participated in a similar session 12 months earlier. For the odometer and texting task conditions the novice drivers showed an improvement in hazard perception and a small but insignificant decrease in task suspension after 12 months. For the scenario with the cell phone task none of the novice drivers suspended the task, nor exhibited any sort of hazard perception behavior at 12 months. The results indicate that although hazard perception generally improves with experience under some distracting task conditions this is not the case for cell phone distractions

Psychosocial factors associated with smoking and drinking among Japanese early adolescent boys and girls: Cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Smoking and drinking alcohol among early adolescents are serious public health concerns, but few studies have been conducted in Japan to assess their prevalence and etiology. A regional survey was conducted in eight schools in two Japanese school districts to identify psychosocial factors associated with smoking and drinking behaviors for boys and girls.</p> <p>Methods</p> <p>Junior high school students from seventh to ninth grades (N = 2,923) completed a self-reported questionnaire between December 2002 and March 2003. Relationships between psychosocial variables (i.e., self-assertive efficacy to resist peer pressure, parental involvement, school adjustment, and deviant peer influence) and smoking and drinking were investigated using logistic regression analyses and path analyses.</p> <p>Results</p> <p>Smoking in the last six months was significantly more prevalent in boys (7.9%) than girls (5.1%). The prevalence of drinking in the last six months was similar in boys (23.7%) and girls (21.8%). Self-efficacy to resist peer pressure was negatively associated with both smoking and drinking among both boys and girls and provided both direct and indirect effects through deviant peer influence. Parental involvement showed indirect effects through school adjustment and/or deviant peer influence to both smoking among both boys and girls and drinking among girls, although parental involvement showed direct effects on smoking only for boys. School adjustment was negatively associated with smoking among both boys and girls and drinking among girls.</p> <p>Conclusion</p> <p>These findings suggest that self-assertive efficacy to resist peer pressure, parental involvement, school adjustment and deviant peer influence are potentially important factors that could be addressed by programs to prevent smoking and/or drinking among early adolescent boys and girls in Japan.</p

Higher self-reported physical activity Is associated with lower systolic blood pressure: The Dietary Intervention Study in Childhood (DISC)

Objective: Children participating in a dietary clinical trial were studied to assess physical activity patterns in boys and girls longitudinally from late childhood through puberty; and to determine the association of level of physical activity on systolic blood pressure (SBP), low density lipoprotein (LDL) cholesterol, and body mass index (BMI). Patients and Methods: In the Dietary Intervention Study in Childhood (DISC), a randomized clinical trial of a reduced saturated fat and cholesterol diet in 8-10 year olds with elevated LDL, a questionnaire that determined time spent in five intensity levels of physical activity was completed at baseline and at 1 and 3 years. A MET score was calculated for weekly activity; hours per week were calculated for intense activities. We hypothesized that weekly self-reported physical activity would be associated with lower SBP, LDL, and BMI over three years. Longitudinal data analyses were performed for each outcome (SBP, LDL, and BMI) using generalized estimating equations with MET score per week as the independent variable adjusted for visit, gender, and Tanner stage (BMI was included in models for SBP and LDL). Results: The initial study cohort comprised 663 youths (362 male; age 9.7 years, 301 female; age 9.0 years) of whom 623 (94%) completed the 3-year visit. For every 100 MET-hours of physical activity, there was a decrease of 1.15 mmHg of SBP (p=0.0038). There was a 1.28 mg/dl decline in LDL (p=0.10) for a similar energy expenditure. For BMI, an analysis of intense physical activity showed that for every 10 hours of intense activity, there was a trend toward significance with a 0.2 kg/m2 decrease (p=0.06). Conclusion: Children with elevated cholesterol who lead a more physically active lifestyle have lower SBP and a trend toward lower LDL over a 3-year interval. Long-term participation in intense physical activity may reduce BMI as well

Decreases in adolescent weekly alcohol use in Europe and North America: evidence from 28 countries from 2002 to 2010

Background: This study examined trends in adolescent weekly alcohol use between 2002 and 2010 in 28 European and North American countries. Methods: Analyses were based on data from 11-, 13- and 15-year-old adolescents who participated in the Health Behaviour in School-Aged Children (HBSC) study in 2002, 2006 and 2010. Results: Weekly alcohol use declined in 20 of 28 countries and in all geographic regions, from 12.1 to 6.1% in Anglo-Saxon countries, 11.4 to 7.8% in Western Europe, 9.3 to 4.1% in Northern Europe and 16.3 to 9.9% in Southern Europe. Even in Eastern Europe, where a stable trend was observed between 2002 and 2006, weekly alcohol use declined between 2006 and 2010 from 12.3 to 10.1%. The decline was evident in all gender and age subgroups. Conclusions: These consistent trends may be attributable to increased awareness of the harmful effects of alcohol for adolescent development and the implementation of associated prevention efforts, or changes in social norms and conditions. Although the declining trend was remarkably similar across countries, prevalence rates still differed considerably across countrie

How Well Do Parents Manage Young Driver Crash Risks

Abstract Motor vehicle crashes are extremely high among young drivers during at least the first year of licensure. Crash risks decline with increased experience, but the more newly licensed teenagers drive, the greater their risk exposure. Hence, the dilemma facing policy makers and parents is how to provide young drivers with driving experience without unduly increasing their crash risk. Graduated driver licensing policies serve to delay licensure and then limit exposure to the highest risk conditions after licensure, allowing young drivers to gain experience only under less risky driving conditions. A similar strategy is needed to guide parents. Parents do not appear to appreciate just how risky driving is for novice drivers and tend to exert less control over their teenage children&apos;s driving than might be expected. Recent research has demonstrated that simple motivational strategies can persuade parents to adopt driving agreements and impose greater restrictions on early teen driving

Not Early Drinking but Early Drunkenness Is a Risk Factor for Problem Behaviors Among Adolescents from 38 European and North American Countries

-Many studies have reported that the earlier the age at first drink (AFDrink) the higher the later drinking levels and related problems. However, unless adolescents proceed into drunkenness, it is unclear why consuming small quantities at early age should lead to later problems. This study investigates the link between AFDrink and problem behaviors (smoking, cannabis use, injuries, fights, and low academic performance) among 15-year-olds who did and did not proceed into drunkenness. Among those with drunkenness experience, we tested whether AFDrink predicted problem behaviors over and above the age at first drunkenness (AFDrunk). Multilevel structural equation models were estimated based on a sample of 44,801 alcohol-experienced 15-year-olds from 38 North American and European countries and regions who participated in the Health Behaviour in School-aged Children cross-national survey. Overall, there was a significant association between AFDrink and all 5 problem behaviors. However, this was the case only among those with drunkenness experiences but not among those never drunk. Among the former, AFDrunk was a strong predictor for all 5 problem behaviors, but time from first drink to first drunk did not predict problem behaviors. Not early alcohol initiation but early drunkenness was a risk factor for various adolescent problem behaviors at the age of 15, that is, there was not consistent relationship for the time before the first drunkenness (i.e., since first drinking). Besides targeting early drinking, particular efforts are needed to impede early drunkenness to prevent associated harm in adolescence and beyond.Det er ikke tidlig alkoholdebut, men tidlig beruselsesdebut som øker risiko for problematferd blant ungdom. Mange studier har rapportert at jo yngre man er når man drikker alkohol for første gang, jo høyere er risikoen for problematferd. Imidlertid viser en ny studie utført av en internasjonal forskergruppe at det ikke er avgjørende om man har debutert tidlig med å drikke, men om man har debutert tidlig med å drikke seg full. Denne studien undersøkte i hvilken grad «alder ved første alkoholinntak» og «alder ved første gang med overstadig beruselse» var assosiert med fem typer av problematferd. De fem typene problematferd var røyking, cannabisbruk, utsatthet for skader, slagsmål og dårlige skoleprestasjoner. Nesten 45 000 15-åringer fra 38 land og regioner i Nord-Amerika og Europa deltok i studien og svarte på spørreskjema. Studien fant en sterk sammenheng mellom det å drikke seg full i ung alder og alle de fem typene problematferd. Jo yngre ungdommene var den første gangen de var fulle, desto større grad av problemer hadde de. En tilsvarende sammenheng ble ikke funnet med hensyn til alder for første gangs alkoholinntak blant dem som ikke hadde vært fulle. Tidlig alkoholdebut så ikke ut til å spille noen rolle for disse ungdommene

Passenger Age and Gender Effects on Adult Driver Fatal Crash Rate

Driver behavior and crash rates vary with the presence of passengers but the details of this relationship are not well understood. The literature generally does not take into account the characteristics of passengers, yet effects on crashes may vary dramatically with passenger age and gender. This study estimated the amount of exposure (driving miles) done by various driver age/gender categories with various combinations of passengers. Statistical imputation techniques were used to derive travel estimates for various pairings using data from the 2001 National Household Travel Survey. Crash frequencies for every pairing were obtained from the Fatality Analysis Reporting System and were used to compute fatal crash rates (per 10 million trip miles). The findings reported here focus on adult (21 and older) drivers. The results show that drivers of a given type (age/gender group) show dramatically different crash rates as a function of passenger type. Some passenger types are associated with fatal crash rates higher than that with no passenger, while other passenger types are associated with lower crash rates. The details of this relationship depend to some degree on driver characteristics. Crash rates for different driver age/gender groups overlap substantially based on the passenger, so that the “best” and “worst” driver groups are passenger-specific. For adult male drivers, female passengers are generally associated with lower crash rates. For male drivers, there is a higher crash rate with a male passenger of a given age than with a female passenger of the same age, even for child passengers

Measuring Young Drivers’ Behaviors during Complex Driving Situations

Driving behaviors of teenagers and adults in complex driving situations, viz., merges and intersections, from an 18-month longitudinal naturalistic driving study were analyzed. Variables from multiple sources were selected to create an Unsafe Driving Index to rate drivers’ behaviors in these locations. Teenagers scored lower on this index, corresponding to safer driving behaviors, than adults. However, the teenagers’ scores for the index increased across the study period. The interpretations of these findings are discussed with respect to the methodological aspects of the study and in terms of driver training and rule following