Reexamining the association between smoking and periodontitis in the dunedin study with an enhanced analytical approach.

BACKGROUND: Smoking is a major risk factor for periodontal disease. Conventional oral epidemiology approaches have found strong, consistent associations between chronic smoking and periodontal attachment loss (AL) through ages 26, 32, and 38 years, but those statistical methods disregarded the data's hierarchical structure. This study reexamines the association using hierarchical modeling to: 1) overcome the limitations of an earlier approach (trajectory analysis) to the data and 2) determine the robustness of the earlier inferences. METHODS: Periodontal examinations were conducted at ages 26, 32, and 38 years in the Dunedin Multidisciplinary Health and Development Study. The number of participants examined at those three ages were 913, 918, and 913, respectively. A generalized linear mixed model with a quasi-binomial approach was used to examine associations between chronic smoking and periodontal AL. RESULTS: At ages 26, 32, and 38, smokers had 3.5%, 12.8%, and 23.2% greater AL than non-smokers. Regular cannabis use was associated with greater AL after age 32, but not at age 26. Males had more AL than females. Participants with high plaque scores had consistently greater AL; those who were of persistently low socioeconomic status had higher AL at ages 32 and 38, but not at age 26. The amount of AL in anterior teeth was less than in premolars and molars. Gingival bleeding was associated with higher AL at ages 26, 32, and 38. CONCLUSION: The smoking-periodontitis association is observable with hierarchical modeling, providing strong evidence that chronic smoking is a risk factor for periodontitis.

Capture-recapture using multiple data sources: estimating the prevalence of diabetes.

OBJECTIVE: To examine the potential for using multiple list sources and capture-recapture methods for estimating the prevalence of diagnosed diabetes. METHOD: A model-averaging procedure using an adjusted Akaike's Information Criterion (QAICc) was used to combine capture-recapture estimates from log-linear models obtained from simultaneously analysing four sources of data. The method was illustrated using four separate lists of patients with diabetes, resident in Otago, New Zealand. RESULTS: Eighteen candidate models with a QAICc weight of more than 0.01 were obtained. A total of 5,716 individuals were enrolled on one or more of the four lists, of whom 379 (6.6%) appeared on all four lists and 1,670 (29.2%) appeared on one list only. The model-averaged estimate of the total number of people with diagnosed diabetes was 6,721 (95% CI: 6,097, 7,346). The age-standardised prevalence was 3.70% (95% CI: 3.36-4.04%) for the total population and 4.45% (95% CI: 4.03-4.86) for adults aged 15+ years. CONCLUSIONS: Estimated diabetes prevalence was consistent with national survey results. Capture-recapture methods, combined with model averaging, are a cheap, efficient tool to estimate the prevalence of diagnosed diabetes. IMPLICATIONS: This method provides a relatively easy way to estimate the prevalence of diagnosed diabetes using routinely collected diabetes information, thus providing the opportunity to monitor the diabetes epidemic and inform planning decisions and resource allocation.

COMPARATIVE BIOCHEMICAL GENETICS OF THREE FIRE ANT SPECIES IN NORTH AMERICA, WITH SPECIAL REFERENCE TO THE TWO SOCIAL FORMS OF SOLENOPSIS INVICTA (HYMENOPTERA: FORMICIDAE).

An electrophoretic study of the genetics of three fire ant species in North America was undertaken with the primary objective of further clarifying the genetic relationship between two social forms of Solenopsis invicta. Such social forms are common in many groups of ants and may, in some cases, represent significant intermediate stages in the speciation process. The monogyne and polygyne forms of S. invicta, while differing in a number of important biological traits, are genetically indistinguishable, in contrast to the substantial genetic differentiation observed between S. invicta and a second, closely related, introduced species, S. richteri. The native fire ant, S. geminata, is genetically the most distinct of the three species studied, in accord with its taxonomic placement in a different species complex. Hypotheses concerning the derivation of the polygyne form of S. invicta from the monogyne form which invoke their long-term reproductive isolation in South America and separate introductions to North America appear unfounded. Although S. invicta and S. richteri are known to hybridize in North America, our study provided no evidence of gene introgression between S. invicta and the native species, S. geminata, in areas where our samples were collected. Analyses of population structure in S. invicta failed to reveal significant differentiation of populations or local inbreeding. Levels of genetic diversity in the three species studied, although not significantly different, were in the order predicted from knowledge of the population biology and recent history of the taxa, with S. richteri exhibiting the least diversity, S. geminata the greatest, and S. invicta having an intermediate level.

BIOCHEMICAL PHENOTYPIC AND GENETIC STUDIES OF TWO INTRODUCED FIRE ANTS AND THEIR HYBRID (HYMENOPTERA: FORMICIDAE).

Two introduced fire ants, Solenopsis invicta and S. richteri, and their hybrid were studied using phenotypic markers from gas chromatographic analysis of hydrocarbons and venom alkaloids, as well as genetic markers from enzyme electrophoresis. Both methods show that extensive gene introgression is occurring over a distance of at least 120 km at the contact zone between the two forms in eastern Mississippi. Genetic analyses suggest that the hybrid population does not depart dramatically from panmixia. Also, recombinant genotypes predominate in the hybrid zone, indicating that F1 hybrids are viable. Allele frequency clines through the hybrid zone are apparent for four polymorphic loci. Data sets generated by the chromatographic and electrophoretic methods are highly concordant in that they differentiate completely between the two forms and agree in designating colonies from the contact zone as hybrid or parental in a high proportion (90%) of cases. The two methods can serve as complementary tools for studying closely related but genetically distinct populations in this, and perhaps other, groups of insects.

GENETIC ORIGIN OF MALE DIPLOIDY IN THE FIRE ANT, SOLENOPSIS INVICTA (HYMENOPTERA: FORMICIDAE), AND ITS EVOLUTIONARY SIGNIFICANCE.

Male diploidy was studied in natural populations of the fire ant, Solenopsis invicta, in order to find an explanation from population genetics for the apparently common occurrence of this phenomenon in some North American populations. The association of male diploidy with polygyne (more than one queen per colony) populations in this species led us to expect that the two phenomena are causally linked. We proposed three hypotheses, based on current knowledge of sex-determining mechanisms in the Hymenoptera, to explain the loss of genetic diversity associated with high rates of diploid male production in S. invicta: a) allelic diversity was reduced during colonization of North America by a small founder group; b) allelic diversity was reduced during subsequent subfounding of the several polygyne populations; and c) genetic structuring of polygyne populations due to local inbreeding caused reduced allelic diversity and/or increased homozygosity. An extensive survey revealed that diploid males are common in all four polygyne (P) populations studied, and that none occur in the monogyne (M) population in north-central Georgia. On the other hand, newly mated (i.e., colony-founding) queens from this same M population produced diploid males in the laboratory, and in the Georgia M and P populations, the frequencies of queens that produce diploid males were shown to be similar. We conclude that the frequent production of diploid males in S. invicta has resulted from a loss of allelic diversity during colonization of North America rather than from any special genetic attribute of P populations. We found no evidence for genetic structuring of the Georgia P population or for decreased allelic diversity relative to the Georgia M population. Thus, the exclusive occurrence of diploid males in P populations does not reflect a fundamental difference between P and M populations in the genetic determinants of male diploidy but is, rather, the result of differential mortality of diploid-male-producing colonies of the two forms. In view of these results, the common occurrence of male diploidy in the P form of S. invicta cannot be taken as evidence of a role for kin selection in the evolution of polygyny. (In this paper, "polygyny" is used to refer to a multiple-queen society.) Studies of the progeny of single queens with allozyme markers demonstrated that diploid male S. invicta are produced biparentally, as in other hymenopteran species. Diploid males were found to take part in the normal summer mating flights in the Georgia P population, although the significance of this behavior is unknown. Males sampled from two P populations exhibited bimodal size distributions, with the diploid males consistently larger than haploids. Assuming a single locus sex determinant, we estimate 15 alleles at this locus for both forms of the ant in North America.