Assessing Injuries with Proxies: Implications for Understanding Concurrent Relations and Behavioral Antecedents of Pediatric Injuries

Assessing Injuries with Proxies: Implications for Understanding Concurrent Relations and Behavioral Antecedents of Pediatric Injuries Bryan T. Karazsia*, MA, and Manfred H. M. van Dulmen, PHD Kent State University Objective To examine the implications of using proxies of medically attended injuries (minor injuries and close calls) for understanding concurrent relations among—and behavioral antecedents of—pediatric injuries. Methods Participants were 812 children from the NICHD Study of Early Child Care. Measures of externalizing behavior, maternal depression, SES, and the home environment were examined as prospective predictors of minor injuries, close calls, and medically attended injuries. Results Minor injuries and close calls were associated with medically attended injuries concurrently. Regression equations revealed different prospective predictors across the three outcome variables. Conclusions This study was the first to examine concurrent associations among minor injuries, close calls, and medically attended injuries. Prospective antecedents of each injury assessment were also examined. The present findings signify the importance of distinguishing between these different methods of assessing pediatric injury. The study also illustrated that different analytic strategies were needed to represent observed data of each outcome variable. Key words injury; injury proxies; count outcomes. Injuries pose a significant threat to the health of children (Peterson & Brown, 1994; U.S. Department of Health and Human Services, 2000), accounting for more deaths in the United States than any other cause (e.g., Martin et al., 2008). Injuries are difficult to study on the individual level because of a variety of methodological and ethical issues with observing injury risk behavior (Peterson & Brown, 1994; Peterson, Saldana, & Heiblum, 1996). Therefore, many researchers utilize proxies of severe injuries, such as minor injuries or ‘‘close calls’’ (e.g., Damashek et al., 2005; Morrongiello, 1997). However, the extent to which assessments of medically attended injuries and various proxies can be used interchangeably is not well established. The purpose of the present study was to examine the extent to which children’s minor injuries and close calls are related with medically attended injuries. Antecedents of each injury variable were also examined. An additional overarching goal of the current study was to explore statistical methodologies appropriate for count outcomes with different distributions (Karazsia & van Dulmen, 2008). Methodological ‘‘Problems’’ with Injury Outcomes For decades, scholars stressed the importance of identifying behavioral antecedents of children’s injuries (Peterson et al., 1996; Scheidt, 1988), though doing so is difficult for several reasons. Childhood injuries are highly reactive (Peterson et al., 1996). That is, they occur less often in the context of supervision (Schwebel, 2006), which makes them difficult to observe directly. Even if injuries could be observed in natural environments, there are obvious ethical problems with doing so without implementing prevention efforts (e.g., Peterson et al., 1996). Furthermore, injury data present a host of ‘‘problems’’ from a statistical standpoint. The most common approach to measuring injury risk is to sum the number of injury events that occur during a specified time period. At the individual level, severe injurious experiences are a low base rate phenomenon (Peterson et al., 1996), which leads to low variability and highly skewed distributions (Karazsia & van Dulmen, 2008). These characteristics present problems because (a) variability is necessary to demonstrate meaningful relations among variables (Cohen, Cohen, *Present address: Department of Psychology, The College of Wooster, Wooster, OH 44691. All correspondence concerning this article should be addressed to Bryan T. Karazsia, Department of Psychology, The College of Wooster, Wooster, OH 44691, USA. E-mail: Journal of Pediatric Psychology 35(1) pp. 51–60, 2010 doi:10.1093/jpepsy/jsp036 Advance Access publication May 18, 2009 Journal of Pediatric Psychology vol. 35 no. 1 ß The Author 2009. Published by Oxford University Press on behalf of the Society of Pediatric Psychology. All rights reserved. For permissions, please e-mail: 52 Karazsia and van Dulmen West, & Aiken, 2003) and (b) highly skewed distributions violate assumptions of common statistical techniques, which often leads to inaccurate results (Hammer & Landau, 1981; Gardner, Mulvey, & Shaw, 1995). Common analytic methods to overcome these problems include dichotomizing data into two groups (i.e., those injured versus not injured) or transforming the data (e.g., Johnson & Wichern, 1998), although it may be more appropriate to use regression techniques designed specifically for count outcomes. In an analysis of medically attended injuries that occurred when children were in the second through sixth grades, Karazsia and van Dulmen (2008) demonstrated that a zero-inflated Poisson (ZIP) model provided the best fit of observed injury data, compared to Ordinary Least Squares, Poisson, negative binomial, and zero-inflated negative binomial models (ZINB).1 Injury Proxies Injury researchers also rely on alternative assessment methods, or proxies, to overcome the aforementioned problems. When proxies are utilized, it is assumed that they adequately represent the phenomenon of interest, in this case severe injury (e.g., Damashek et al., 2005). Multiple proxies of medically attended injuries exist in the literature, including counting the number of minor injuries and close calls. An attractive feature of these proxies is that they occur at a higher frequency than severe injuries. Therefore, different analytic strategies may be required to model the different distributions appropriately. To our knowledge, this issue has never been explored empirically, and thus one goal of this paper was to explore statistical techniques that may be useful for these outcomes. Assessing minor injuries is a common practice established by Peterson and colleagues (Peterson & Brown, 1994; Peterson et al., 1996). Minor injuries are an attractive proxy of medically attended injuries because they have higher base rates, although research on the extent to which they are related with medically attended injuries is mixed. For example, Morrongiello, Ondejko, and Littlejohn (2004) reported that minor injuries correlated positively with retrospective reports of more severe injuries, while Schwebel, Binder, and Plumert (2002) reported no significant relationship between minor injuries and retrospective reports of medically attended injuries. To our knowledge, no studies have investigated the 1 For a thorough description of these and other regression models, including mathematical equations, please consult Long and Freese (2006). extent to which minor injuries are associated concurrently with medically attended injuries. Ano (...truncated)