Robert D. Hoppa

Geographic analysis of diabetes prevalence in an urban area

The objective of this research is to identify the sociodemographic, environmental, and lifestyle factors associated with the geographic variability of Diabetes Mellitus (DM) prevalence in the City of Winnipeg, Manitoba in Canada. An ecological regression study design was employed for this purpose. The study population included all prevalent cases of DM in 1998 for Winnipeg. Predictor and outcome data were aggregated for analysis using two methods. First, the spatial scan statistic was used to aggregate study data into highly probable diabetes prevalence clusters. Secondly, predictor and outcome data were aggregated to existing administrative health areas. Analysis of variance and spatial and non-spatial linear regression techniques were used to explore the relationship between predictor and outcome variables. The results of the two methods of data aggregation on regression results were compared. Mapping and statistical analysis revealed substantial clustering and small-area variations in the prevalence of DM in the City of Winnipeg. The observed variations were associated with variations in socioeconomic, environmental and lifestyle characteristics of the population. The two methods of data aggregation used in the study generated very similar results in terms of identifying the geographic location of DM clusters and of the population characteristics ecologically correlated to those clusters. High rates of DM prevalence are strongly correlated with indicators of low socioeconomic status, poor environmental quality and poor lifestyles. This analysis further illustrates what a useful tool the spatial scan statistic can be when used in conjunction with ecological regression to explore the etiology of chronic disease.

Population variation in osteological aging criteria: An example from the pubic symphysis

A fundamental assumption made by skeletal biologists is that both the pattern and rate of age-related morphological changes observed in modern reference populations are not significantly different than in past populations. In this brief exploration, the composition of a single reference and two independent, known-age, target samples are evaluated for the pubic symphysis. Differences in the timing of age-progressive changes between the reference and target samples are observed, and in particular, females demonstrated a pattern that was fundamentally different from the reference sample. These results serve as a cautionary note for the use of osteological aging criteria and issues of representativeness for modern standards.

A test of sex determination from measurements of chest radiographs.

Sexually dimorphic distinctions within the human thoracic area may include morphological as well as metric differences in the sternum and 4th rib. This research assesses the validity of a set of previously published measurements from chest radiographs and their use in contemporary forensic situations. The chest plates from 130 adult individuals of a known sample undergoing medico-legal post-mortem examination were examined at autopsy. Thoracic radiographs were taken using a Faxitron cabinet X-ray machine at 40 kV using Kodak Diagnostic Film Ready Pack X-Omat TL. Measurements were taken to the nearest millimetre using a sliding calliper. Logistic regression analysis of measurements of the sternum and 4th rib was undertaken to determine sex. Using 4th rib width and sternal area, sex was predicted at an accuracy of 95.8% for males and 90.3% for females.

Sex Allocation from Long Bone Measurements using Logistic Regression

ABSTRACTLogistic regression equations are more suitable for the prediction of sex than other multivariate statistical techniques such as least squares linear regression or discriminant function ana...

Estimating diaphyseal length from fragmentary subadult skeletal remains : Implications for palaeodemographic reconstructions of a southern Ontario ossuary

Fragmentary skeletal remains are a significant problem for osteologists attempting to reconstruct individuals or populations. This problem is further aggravated by sites yielding commingled remains, such as are recovered from the large protohistoric and historic ossuaries from southern Ontario, for which individual methods of age estimation and sex determination cannot be used concurrently. While some attention has been given to the estimation of long bone length from fragmentary, adult remains, little attention has been given to the equally important problem of fragmentary long bones in subadult assemblages. Analysis of data on diaphyseal length is a crucial aspect of reconstructing subadult palaeodemographic profiles, particularly for ossuary collections where dental remains are not associated with individuals and are often less represented than long bones. Such analysis also aids in the assessment of conditions of past population health. This study reports the results of several regression techniques used to estimate diaphyseal length from shaft-end breadths. Data collected from two southern Ontario ossuary samples were compiled to calculate the regression equations. Reliability of these equations and implications for palaeodemographic profiles are discussed.

Two quantitative methods for rib seriation in human skeletal remains.

Accurate rib sequencing is of importance to both forensic anthropologists and human osteologists, but until recently there have been few traits used to aid in the seriation of ribs within a human burial. This study examines two measurements (head to tubercle length and superior costotransverse ligament crest height) for the purpose of aiding rib identification and seriation in human skeletal remains. A sample of 344 ribs from 43 individuals from the 19th century Anglican Church cemetery of St. Thomas in Belleville, Ontario were used for the current study. While the head to tubercle length appeared unreliable for rib seriation, the superior costotransverse ligament crest height may provide an alternative technique for assessing rib sequence. More importantly though, the method provides a basis on which the identification of the central ribs can be made.

Assessing Age-Related Morphology of the Pubic Symphysis from Digital Images Versus Direct Observation

The increasingly global role of a forensic anthropologist necessitates a proper means for archiving evidence for re-examination. Large quantities of evidence can be stored and be made readily accessible through digital imaging. This study focuses on age assessment from digital photographs for personal identity reconstructions. A comparison of 52 Suchey-Brooks scores assigned to digital images and actual bone revealed that age assessment from digital images can be completed with accuracy. Coefficients of concordance imply that there significant agreement between osteological assessment of aging criteria from digital images and direct observation-greater than random change alone (p < 0.05). However, assessments from images should be approached with caution since there are inherent limitations of the naked eye in identifying morphological changes in certain skeletal features, especially where older adults are concerned. Although there is no replacement for a hands-on physical assessment, a digital archive may facilitate the global needs of the forensic anthropologist.

A re-evaluation of the impact of radiographic orientation on the identification and interpretation of Harris lines.

The identification of Harris lines through radiographic analysis has been well-established since their discovery in the late nineteenth century. Most commonly associated with stress, the study of Harris lines has been fraught with inconsistent identification standards, high levels of intra- and interobserver error, and the inevitability of skeletal remodelling. Despite these methodological challenges, the use of Harris lines remains an important contributor to studies of health in archaeological populations. This research explores the radiographic process, specifically orientation and how Harris lines are initially captured for study. Using the Black Friars (13th-mid 17th centuries) skeletal sample from Denmark, 157 individuals (134 adults; 23 subadults) were radiographically analyzed in both an anterior-posterior (A-P) and medial-lateral (M-L) view for the left and right radii and tibiae. Based on the current methodological standards within the literature, it was hypothesized that the A-P view would provide the best resolution and visualization of Harris lines. The results, however, show that the number of lines visible in the M-L view were significantly higher than those visible in the A-P view; inferring that the M-L view is superior for the study of Harris lines.

The MAD legacy: How meaningful is mean age-at-death in skeletal samples

This study examines the representativeness of palaeodemographic reconstructions from human skeletal remains. Mean age-at-death (MAD) is the primary statistic used in interpretations of changing patterns of health and well being from palaeodemographic analyses. A series of sampling experiments were conducted on three documented 19th century samples representing the total cemetery population from which skeletal samples could be drawn. Comparisons of the age-at-death distributions of simulated skeletal samples to the parent population were made to assess the relative magnitude of deviation associated with different types of bias (age, sex, temporal). From the examples presented, variability in age-at-death distribution is high in samples of less than 100, suggesting that for samples of less than 100analyzable individuals, it is probable that the mortality profiles constructed are not an accurate reflection of the cemetery. It is proposed that whateverprocess mean age-at-death reflects for past populations (fertility or mortality), is irrelevant if the sample on which the statistic is calculated is not representative of the population. Given that most cemetery samples will be subject, differentially, to biases at a variety of levels, comparative studies based on palaeodemographic data cannot be considered reliablewithout careful control for those biases. It is suggested that representativeness is the primary theoretical obstacle for researches to overcome, and that it is necessary to shift our focus to rigorously exploring those factors that bias our samples. Without some direct quantification of the representativeness of a sample, palaeodemographic estimators such as mean age-at-death are meaningless and any subsequent interpretations regarding the past, dubious at best.

The biochemical signatures of stress: A preliminary analysis of osteocalcin concentrations and macroscopic skeletal changes associated with stress in the 13th - 17th centuries black friars population.

OBJECTIVE As a chemical precursor to the hard tissue changes well-studied in bioarchaeological research, osteocalcin provides a unique opportunity to assess stress via fluctuations in bone metabolism. The main objectives of this research were 1) to successfully extract osteocalcin from the Black Friars skeletal population; 2) to assess the diagenetic change between individual bone samples; and 3) to compare osteocalcin concentrations across sex, age, time period and macroscopic indicators of stress. METHODS Twenty adult individuals were selected from the 13th-17th centuries Black Friars skeletal population with bone samples taken from the clavicle and femur. Total protein was assessed through a MicroBCA analysis with osteocalcin quantified using a Human Quantikine ELISA kit. Diagenetic change was assessed using Fourier transform infrared spectroscopy and the attenuated total reflectance method. RESULTS Osteocalcin concentrations showed no significant differences between sex or age groups; however, between time period the post-medieval individuals showed a significant reduction of osteocalcin in both the clavicle and the femur. There were no significant differences in osteocalcin concentrations between those with and without past stress indicators and only one significant difference among the chronic indicators. The diagenetic results demonstrated a similar degree of crystallinity between all samples. CONCLUSIONS While preliminary in nature, this study was successful in demonstrating the potential use of osteocalcin in future health-related research and how the study of osteocalcin may contribute to a better understanding of how and when stress begins to affect the skeletal tissues.