Regressões lineares em geocronologia: isócronas, errócronas e pseudoisócronas

Several methods of linear regression reported in the literature for use in geochonology are discussed in order to guide geochronologists in the selection of an adequate model and also to distinguish among isochrons, errorchrons and pseudoisochrons. For Rb/Sr isochron methods, at least 6 models or statistical treatments are available, each one with its peculiarities. Based in two examples, we show that for cases when the experimental data points scatter within limits determined by the experimental errors, and using or not the weighted regression treatment, the resultant parameters are essentially concordant. The estimates of associated error, however especially for initial ratios, show variations by up to a factor of 7, depending upon the statistical procedure. In view of this fact and on the basis of simulated test data, we propose not only more adequate models, but also general criteria that must be observed in the selection of samples in order to obtain an isochron. If the data to be regressed show a scatter in excess of experimental error for geological reasons (open system), four regression models are available to treat the parameters defined in these cases as errorchrons. These models are briefly discussed in terms of their applications. In the Pb/U methods, in which the usual regression treatment is applied to obtain the best-fit line, some additional peculiarities are pointed outDiversos métodos de regressão linear propostos na literatura, para fins geocronológicos, são discutidos de modo a orientar os geocronólogos na escolha de modelos adequados e também distinguir entre isócronas, errócronas ou pseudoisócronas. No caso do método isocrôni co Rb/Sr, são disponíveis pelo menos 6 modelos ou abordagens estatísticas, cada qual com peculiaridades específicas. Exemplifica-se o caso em que os pontos se alinham dentro dos erros experimentais e utilizando modelos, adequados ou não, que empregam a técnica de pondera ção dos pontos, os parâmetros resultantes são praticamente concordantes, porém os erros podem variar até por um fator tão alto quanto 7, conforme a formulação estatística proposta. Em vista deste fato, propõem-se, com base também em exemplos, os modelos mais adequados e também critérios gerais que devem ser observados até na seleção de amostras para a obtenção de isócronas. Nos casos em que os pontos não se alinham dentro dos erros experimentais, por causas geológicas (sistema aberto), são abordados 4 dos modelos sugeridos e é feita também uma discussão em que casos seriam aplicáveis. No método da concórdia Pb/U, em que as regressões usuais também são aplicáveis para determinar a melhor reta, algumas particularidades adicionais são discutida

Relationship between tooth loss and mortality in 80-year-old Japanese community-dwelling subjects

<p>Abstract</p> <p>Background</p> <p>Findings from several studies suggest associations between tooth loss and health outcomes, including malnutrition, poor quality of life, and mortality, in older individuals. However, limited information is available regarding whether those associations remain true in very elderly subjects after adequately considering confounding factors such as sex and smoking status. Herein, we determined whether the number of teeth in 80-year-old subjects is an independent predictor of mortality.</p> <p>Methods</p> <p>We initially contacted 1282 80-year-old community-dwelling individuals born in 1917, of whom 697 responded and participated in a baseline study, with follow-up examinations conducted 4 and 5.5 years later. Data from interviews and medical and oral examinations were obtained, and oral health was determined according to the number of teeth remaining in the oral cavity.</p> <p>Results</p> <p>A total of 108 and 157 subjects died in 4 years and 5.5 years, respectively, after the baseline study. Tooth loss was significantly associated with mortality at age 85.5, but not at age 84, after adjusting for potential confounders. When the analysis was stratified by sex, we found a stronger association in females in follow-up examinations conducted at both 4- and 5.5 years. On the other hand, the effect of tooth loss on mortality was not significantly different between smokers and non-smokers.</p> <p>Conclusion</p> <p>Tooth loss is a significant predictor of mortality independent of health factors, socio-economic status, and lifestyle in octogenarians, with a stronger association in females.</p

Idades K-Ar de rochas alcalinas do Brasil meridional e Paraguai oriental: compilação e adaptação às novas constantes de decaimento

A compilation of 295 geochronological data of 52 alkaline occurrences from Southern Brazil and Eastern Paraguay is presented. These data, mostly available in previous publications, were recalculated, using the new decay constants recommended by STEIGER & JAEGER (1977) for the K-Ar method. The estimated analytical error of the age determined using experimental parameters is also indicated (COX & DALRYMPLE, 1967). This paper aims, specifically, at making ages published prior to 1977 compatible with recent data, allowing, for example, comparisons between ages obtained from a single alkaline massif or from neighbouring massifs. By calculating K-Ar ages using the constants recommended by STEIGER & JAEGER (op. cit.), there occurs an increase of 2.1 to 2.4% in the value of the age calculated with the previous constantsUma compilação de 295 dados geocronológicos de 52 ocorrências alcalinas do Brasil Meridional e Paraguai Oriental é apresentada. Estes dados, previamente publicados em sua quase totalidade, foram recalculados, utilizando-se as novas constantes de decaimento recomendadas por STEIGER & JAEGER (1977) para o método K-Ar. Indica-se, também, a estimativa do erro analítico da idade, determinada em função das condições experimentais (COX & DALRYMPLE 1967). O presente trabalho visa, especificamente, compatibilizar as idades publicadas anteriormente a 1977 com os dados mais recentes, permitindo, por exemplo, comparações entre idades de um mesmo maciço alcalino ou de maciços alcalinos vizinhos. Ao se calcular a idade K-Ar utilizando-se as constantes de STEIGER & JAEGER (op. cit.) ocorre um acréscimo de 2,1 a 2,4% no valor da idade calculada pelas constantes anteriore

Serum total cholesterol concentration and 10-year mortality in an 85-year-old population

Yutaka Takata,1 Toshihiro Ansai,2 Inho Soh,2 Shuji Awano,2 Ikuo Nakamichi,1 Sumio Akifusa,3 Kenichi Goto,1 Akihiro Yoshida,2 Hiroki Fujii,1 Ritsuko Fujisawa,1 Kazuo Sonoki3 1Division of General Internal Medicine, 2Division of Community Oral Health Development, 3Department of Oral Health and Environment, School of Oral Health Science, Kyushu Dental College, Kitakyushu, Japan Abstract: Little is known about the association between total cholesterol (TC) and all-cause mortality in the elderly (especially the very elderly). Here we examined the association between TC and all-cause mortality in 207 very elderly (85-year-old) participants. In 2003, we performed a baseline laboratory blood examination, and blood pressure (BP) and body mass index (BMI) measurements, and lifestyle questionnaires were completed by the participants. The participants were followed for the subsequent 10 years. As of 2013, of the 207 participants in 2003, 70 participants had survived, 120 individuals had died, and 17 were lost to follow up. The TC values were divided into high-TC (&ge;209 mg/dL), intermediate-TC (176&ndash;208 mg/dL), and low-TC (&le;175 mg/dL) categories. With the Kaplan&ndash;Meier method, we found that both the high-TC and intermediate-TC participants survived longer than the low-TC participants. The men with high TC survived longer than those with low TC, but no corresponding difference was found for the women. A multivariate Cox proportional hazards regression model, with adjustment for gender, smoking, alcohol intake, history of stroke or heart disease, serum albumin concentration, BMI, and systolic BP, revealed that the total mortality in the low-TC group was 1.7-fold higher than that in the high-TC group. Mortality, adjusted for the same factors, decreased 0.9% with each 1 mg/dL increase in the serum TC concentration and decreased 0.8% with each 1 mg/dL increase in the serum (low-density lipoprotein) LDL-cholesterol (LDL-C) concentration. Our results indicate an association between lower serum TC concentrations and increased all-cause mortality in a community-dwelling, very elderly population. Mortality decreased with the increases in both TC and LDL-C concentrations, after adjustment for various confounding factors. These findings suggest that low TC and low LDL-C may be independent predictors of high mortality in the very elderly. Keyword: community-dwelling, very elderly, LDL-cholesterol, gender difference, prospective cohor

High-level activities of daily living and disease-specific mortality during a 12-year follow-up of an octogenarian population

Yutaka Takata,1 Toshihiro Ansai,2 Inho Soh,2 Shuji Awano,2 Ikuo Nakamichi,1 Sumio Akifusa,3 Kenichi Goto,1 Akihiro Yoshida,2 Hiroki Fujii,1 Ritsuko Fujisawa,1 Kazuo Sonoki31Division of General Internal Medicine, 2Division of Community Oral Health Science, 3Department of Oral Health and Environment, School of Oral Health Science, Kyushu Dental University, Kitakyushu, JapanBackground: Little is known about the relationship between disease-specific mortality and high-level activities of daily living in the elderly. We examined whether mortality is associated with high-level activities of daily living in an octogenarian population.Methods: We conducted a population-based cross-sectional and prospective cohort study in 693 older persons aged 80 years and living in Japan&rsquo;s Fukuoka Prefecture. We then evaluated the association between 12-year disease-specific mortality and high-level functional capacity as measured by the Tokyo Metropolitan Institute of Gerontology Index of Competence, which is a standardized multidimensional 13-item instrument; items 1 through 5 are classified as instrumental self-maintenance activity, items 6 through 9 as intellectual activity, items 10 through 13 as social roles activity, and all 13 items together yield total functional capacity.Results: By the 12-year follow-up of the 693 participants, 413 had died, 242 survived, and 38 were unable to be located. Of the 413 who died, 105 died of cardiovascular disease, 73 of respiratory tract disease, 71 of cancer, and 39 of senility. Of the other 125 deaths, 59 were due to other diseases, and the cause of death for 66 participants is not known. The hazard ratio (HR) for all-cause mortality, adjusted for confounding factors with multivariate Cox analyses, fell by 6% (HR 0.937, 95% confidence interval [CI] 0.899&ndash;0.978, P = 0.003) with each one-point increase in participants&rsquo; scores on the Tokyo Metropolitan Institute of Gerontology Index of total functional capacity. With one-point increases in instrumental self-maintenance activity and in intellectual activity, the HRs for all-cause mortality decreased by 14% (HR 0.856, 95% CI 0.787&ndash;0.930, P = 0.000) and 12% (HR 0.884, 95% CI 0.794&ndash;0.983, P = 0.023), respectively. Respiratory mortality with HR adjustment fell by 11% (HR 0.887, 95% CI 0.804&ndash;0.978, P = 0.016) and 24% (HR 0.760, 95% CI 0.627&ndash;0.922, P = 0.005) with one-point increases in the scores of total functional capacity and instrumental self-maintenance activity, respectively. Similarly, mortality due to senility fell by 16% (HR 0.838, 95% CI 0.743&ndash;0.946, P = 0.004), 29% (HR 0.707, 95% CI 0.564&ndash;0.886, P = 0.003), and 29% (HR 0.710, 95% CI 0.522&ndash;0.966, P = 0.029) with one-point increases in the scores of total functional capacity, instrumental self-maintenance activity, and intellectual activity, respectively.Conclusion: These findings suggest that high-level activities of daily living may be an independent predictor of mortality due to all causes, respiratory disease and senility in older persons.Keywords: older persons, community-dwelling, mortality, respiratory death, instrumental AD

Cognitive function and 10 year mortality in an 85 year-old community-dwelling population

Yutaka Takata,1 Toshihiro Ansai,2 Inho Soh,2 Shuji Awano,2 Ikuo Nakamichi,1 Sumio Akifusa,3 Kenichi Goto,1 Akihiro Yoshida,2 Hiroki Fujii,1 Ritsuko Fujisawa,1 Kazuo Sonoki31Division of General Internal Medicine, Kyushu Dental University, 2Division of Community Oral Health Development, Kyushu Dental University, 3Department of Oral Health and Environment, School of Oral Health Science, Kyushu Dental University, Kitakyushu, JapanAbstract: The relationship between mortality and impaired cognitive function has not been thoroughly investigated in a very elderly community-dwelling population, and little is known about the association of disease-specific mortality with Mini-Mental State Examination (MMSE) subscale scores. Here we evaluated these data in Japanese community-dwelling elderly. In 2003, 85 year-olds (n=207) were enrolled; 205 completed the MMSE for cognitive function and were followed-up for 10 years, during which time 120 participants died, 70 survived, and 17 were lost to follow-up. Thirty-eight deaths were due to cardiovascular disease, 22 to senility, 21 to respiratory disease, and 16 to cancer. All-cause mortality decreased by 4.3% with a 1-point increase in the global MMSE score without adjustment, and it decreased by 6.3% with adjustment for both sex and length of education. Cardiovascular mortality decreased by 7.6% and senility mortality decreased by 9.2% with a 1-point increase in the global MMSE score with adjustment for sex and education. No association was found between respiratory diseases or cancer mortality and global MMSE score. All-cause mortality also decreased with increases in MMSE subscale scores for time orientation, place orientation, delayed recall, naming objects, and listening and obeying. Cardiovascular mortality was also associated with the MMSE subscale of naming objects, and senility mortality was associated with the subscales of time orientation and place orientation. Thus, we found that impaired cognitive function determined by global MMSE score and some MMSE subscale scores were independent predictors of all-cause mortality or mortality due to cardiovascular disease or senility in 85 year-olds.Keywords: cognition, elderly, mortality, community-dwelling, MMS