Douglas A. Noe

Risk Factors of Falls in Community-Dwelling Older Adults: Logistic Regression Tree Analysis

PURPOSE OF THE STUDY A novel logistic regression tree-based method was applied to identify fall risk factors and possible interaction effects of those risk factors. DESIGN AND METHODS A nationally representative sample of American older adults aged 65 years and older (N = 9,592) in the Health and Retirement Study 2004 and 2006 modules was used. Logistic Tree with Unbiased Selection, a computer algorithm for tree-based modeling, recursively split the entire group in the data set into mutually exclusive subgroups and fit a logistic regression model in each subgroup to generate an easily interpreted tree diagram. RESULTS A subgroup of older adults with a fall history and either no activities of daily living (ADL) limitation and at least one instrumental activity of daily living or at least one ADL limitation was classified as at high risk of falling. Additionally, within each identified subgroup, the best predictor of falls varied over subgroups and was also evaluated. IMPLICATIONS Application of tree-based methods may provide useful information for intervention program design and resource allocation planning targeting subpopulations of older adults at risk of falls.

Comparing methods for analyzing overdispersed binary data in aquatic toxicology

Historically, death is the most commonly studied effect in aquatic toxicity tests. These tests typically employ a gradient of concentrations and exposure with more than one organism in a series of replicate chambers in each concentration. Whereas a binomial distribution commonly is employed for such effects, variability may exceed that predicted by binomial probability models. This additional variability could result from heterogeneity in the probabilities across the chambers in which the organisms are housed and subsequently exposed to concentrations of toxins. Incorrectly assuming a binomial distribution for the statistical analysis may lead to incorrect statistical inference. We consider the analysis of grouped binary data, here motivated by the study of survival. We use a computer simulation study to examine the impact of overdispersion or outliers on the analysis of binary data. We compare methods that assume binomial or generalizations that accommodate this potential overdispersion. These generalizations include adjusting the standard probit model for clustering/correlation or using alternative estimation methods, generalized estimating equations, or generalized linear mixed models (GLMM). When data were binomial or overdispersed binomial, none of the models exhibited any significant bias when estimating regression coefficients. When the data were truly binomial, the probit model controlled type I errors, as did the Donald and Donner method and the GLMM method. When data were overdispersed, the probit model no longer controlled type I error, and the standard errors were too small. In general, the Donald and Donner and the GLMM methods performed reasonably based on this study, although all procedures suffered some impact in the presence of potential outliers.

The Psychosocial Effects of Cleft Lip and Palate in Non-Anglo Populations: A Cross-Cultural Meta-Analysis

Objective A meta-analytic study was conducted to examine the cross-cultural psychosocial impact of cleft lip and/or palate in non-Anglo populations. Design A total of 333 citations were initially identified for review using electronic and hand-search strategies. Of the six studies that met inclusion criteria, two were later excluded due to insufficient data. The four remaining studies represented a combined sample size of 2276 adolescents and adults with cleft lip and/or palate from China, Hong Kong, Taiwan, and Norway. Main outcome Measures Effect size using Cohens d and confidence intervals were estimated using data from four studies of empirical, controlled study designs. Results The magnitude of effect sizes indicated that men (d = −0.75) with cleft lip and/or palate in non-Anglo cultures are more prone to psychosocial issues than women (d = −0.33). Adults (d = −0.50) are more impacted than adolescents (d = −0.04). Overall, regardless of age, gender, or culture, individuals with cleft lip and/or palate have lower psychosocial development than individuals without cleft lip and/or palate (d = −0.42). Conclusion The effects for the cross-cultural comparisons were moderated by the age group and gender of the participants; however, most studies resulted in negative effect sizes. Health care teams for cleft lip and/or palate should recognize the importance of psychological intervention and family support in the treatment of all patients with cleft lip and/or palate throughout the life span.

Are body mass and parasite load related to social partnerships and mating in Microtus ochrogaster

Abstract Within socially monogamous species, a males reproductive success depends on his success at obtaining a social partner with which he mates, as well as gaining extra-pair matings. We investigated the impacts of body mass and parasitism on 2 measures of a males success at obtaining a social partner (number of female social associations and relative strength of a social bond to a single female) and 2 measures of reproduction (number of females with which a male sires offspring and the number of offspring sired) in natural populations of prairie voles (Microtus ochrogaster) located in Kansas and Indiana. Kansas males with greater endoparasite loads were less likely to have one social partner. Instead, they associated with multiple females although they did not sire offspring with more females than males with lower levels of endoparasitism. We did not find any relationship between endoparasite infestation and the number of females with which males associated in Indiana. There was no association between the level of endoparasites found among males in either Indiana or Kansas and the strength of a males social bond to a female. Endoparasites, at least at the infection levels detected in this study, were not related to indices of male reproductive success in Microtus populations in Kansas or Indiana. No relationship was found between body mass and indicators of social monogamy in either population. However, body mass appears to be significantly related to male reproductive success. Heavier males produced offspring with more females, particularly in the Kansas population, and sired more pups in both populations.

Predictors of adherence with self-care guidelines among persons with type 2 diabetes: results from a logistic regression tree analysis.

Type 2 diabetes is known to contribute to health disparities in the U.S. and failure to adhere to recommended self-care behaviors is a contributing factor. Intervention programs face difficulties as a result of patient diversity and limited resources. With data from the 2005 Behavioral Risk Factor Surveillance System, this study employs a logistic regression tree algorithm to identify characteristics of sub-populations with type 2 diabetes according to their reported frequency of adherence to four recommended diabetes self-care behaviors including blood glucose monitoring, foot examination, eye examination and HbA1c testing. Using Andersen’s health behavior model, need factors appear to dominate the definition of which sub-groups were at greatest risk for low as well as high adherence. Findings demonstrate the utility of easily interpreted tree diagrams to design specific culturally appropriate intervention programs targeting sub-populations of diabetes patients who need to improve their self-care behaviors. Limitations and contributions of the study are discussed.

Long-Distance Dispersal and Diffusion in the Invasion of Lonicera maackii

Abstract To investigate the relative importance of long-distance dispersal vs. diffusion in the invasion of a nonnative plant, we used age structure to infer the contribution to recruitment of external propagule rain vs. within-population reproduction. We quantified the age structure of 14 populations of Amur honeysuckle in a landscape where it recently invaded, in Darke County, OH. We sampled the largest honeysuckle individuals in each population (woodlots), and aged these by counting annual rings in stem cross sections. Individuals in the oldest four 1-yr age classes are assumed to be from external recruitment, given the minimum age at which shrubs reproduce. We used these recruitment rates to model external recruitment over the next 5 yr and used observed age structures to estimate total recruitment. We used the difference between total and external recruitment to infer the rate of internal recruitment. Our findings indicate that recruitment from within the population is of about the same magnitude as immigration in the fifth to seventh year after population establishment, but by years 8 to 9 internal recruitment dominates. At the landscape scale, the temporal-spatial pattern of population establishment supports a stratified dispersal model, with the earliest populations establishing in widely spaced woodlots, about 4 km from existing populations, and these serving as “nascent foci” for diffusion to nearby woodlots. Understanding the relative importance of long-distance dispersal vs. diffusion will inform management, e.g., whether it is more effective to scout for isolated shrubs or remove reproducing shrubs at the edge of invaded areas. Nomenclature: Amur honeysuckle, Lonicera maackii (Rupr.) Herder. Management Implications: The relative importance of diffusion (expanding front) vs. long-distance dispersal can inform management of invasive species. If diffusion dominates, it will be most efficient to monitor for, and eradicate, new patches on the edges of existing patches. If long-distance dispersal dominates, one should scout for, and eradicate, initial colonists in previously uncolonized patches (Moody and Mack 1988). Furthermore, removing reproductive individuals at the edge of the current range would slow the spread of diffusing populations, but have little effect if long-distance dispersal dominates. We assessed the relative importance of diffusion vs. long-distance dispersal in the invasion of Amur honeysuckle [Lonicera maackii (Rupr.) Herder] in forested patches in an agricultural landscape in southwest Ohio. We examined the age structures of woodlot populations, used these to estimate the importance of immigration vs. within-population recruitment, and examined the temporal-spatial pattern of population initiation. Our findings indicate that long-distance dispersal dominates early in the invasion, and new populations grow slowly, until the original colonists begin reproducing. Thus, efforts to slow the spread of L. maackii should involve scouting for colonists in woodlots up to 4–5 km from existing populations. Fortunately, this is feasible, as even small honeysuckle shrubs are easily spotted during early spring and late fall, when native deciduous woody plants are not in leaf. These searches could be as infrequent as every 3 yr, given the lack of reproduction in the youngest age classes.

Male prairie voles with different avpr1a microsatellite lengths do not differ in courtship behaviour

Females are generally expected to be selective when choosing their social and sexual partners. In a previous laboratory study, female prairie voles (Microtus ochrogaster) showed significant social and sexual preferences for males with longer microsatellite DNA within the avpr1a gene encoding the vasopressin 1a receptor, as predicted if females select mates whose parental behaviour should increase female reproductive success. We tested the hypothesis that males with short versus long avpr1a microsatellite alleles exhibit differences in courtship behaviour, which could act as cues for female mate preference. The only behavioural difference we detected between males with short versus long avpr1a microsatellite alleles in mate preference trials was that males with short avpr1a microsatellite alleles sniffed the anogenital region of females more frequently during the first two days of the trials. Our results did not strongly support the hypothesis that a males avpr1a genotype predicts the courtship behaviours we measured and suggests that other courtship behaviours or traits, such as odour and vocalizations, may be more important to female prairie voles when choosing mates. Additional studies using a wider array of species are needed to assess the degree to which male mammal courtship behaviour provides information on mate quality to females.

Identifying At-Risk Subpopulations of Canadians with Limited Health Literacy

Background. Health literacy, the set of skills for locating, understanding, and using health-related information, is associated with various health outcomes through health behaviors and health care service use. While health literacy has great potential for addressing health disparities stemming from the differing educational attainment in diverse populations, knowledge about subpopulations that share the same risk factors is useful. Objective. This study employed a logistic regression tree algorithm to identify subpopulations at risk of limited health literacy in Canadian adults. Design. The nationally representative data were derived from the International Adult Literacy and Skills Survey (n = 20,059). The logistic regression tree algorithm splits the samples into subgroups and fits logistic regressions. Results. Results showed that the subpopulation comprised of individuals 56 years and older, with household income less than

Here's to Your Health: Will They Stay or Will They Go? Predicting disenrollment from home care services to nursing homes using classification trees

50,000, no participation in adult education programs, and lack of reading activities (i.e., newspaper, books) was at the greatest risk (82%) of limited health literacy. Other identified subgroups were displayed in an easily interpreted tree diagram. Conclusions. Identified subpopulations organized in tree diagrams according to the risk of limited health literacy inform not only intervention programs targeting unique subpopulations but also future health literacy research.

The role of ultraviolet radiation and fish in regulating the vertical distribution of Daphnia

According to the U.S. Department of Health and Human Services, there are 36 million adults over age 65 living in the United States, representing 12% of the population. This segment of the population is expected to increase to more than 70 million by 2030. The number of individuals age 85 and older—who are more likely to be disabled and in need of services for chronic disability than members of the general population—is predicted to increase by 44% between 2005 and 2020. Although the majority of daily custodial care (referred to as long-term care) is paid privately, Medicaid plays a major role. Long-term care services are provided in a variety of settings, including homes, residential care, and nursing facilities. A high proportion of people who disenroll from homecare services leave for nursing homes, and nursing homes are the most expensive option. Policymakers naturally would like to know if any policy interventions would make it possible for the elderly to stay at home longer. A related important question that can be assessed with available data is: Among those individuals who have been enrolled in a homecare services program, who is most likely to disenroll and enter a nursing home? Something Other Than Logistic Regression?