Standard Life Table Research Articles

LOCAL ADAPTATION IN TWO SUBSPECIES OF AN ANNUAL PLANT: IMPLICATIONS FOR MIGRATION AND GENE FLOW.

Plant populations often adapt to local environmental conditions. Here we demonstrate local adaptation in two subspecies of the California native annual Gilia capitata using standard reciprocal transplant techniques in two sites (coastal and inland) over three consecutive years. Subspecies performance in each site was measured in four ways: probability of seedling emergence, early vegetative size (length of longest leaf), probability of flowering, and total number of inflorescences produced per plant. Analysis of three of the four variables demonstrated local adaptation through site-by-subspecies interactions in which natives outperformed immigrants. The disparity between natives and immigrants in their probability of emergence and probability of flowering was greater at the coastal site than at the inland site. Treated in isolation, these two fitness components suggest that migration from the coast to the inland site may be less restricted by selection than migration in the opposite direction. Two measurements of individual size (leaf length and number of inflorescences), suggest (though not strongly) that immigrants may be subject to weaker selection at the coastal site than at the inland site. A standard cohort life table is used to compare replacement rates (R0 ) for each subspecies at each site. Comparisons of R0 s suggest that immigrants are under a severe demographic disadvantage at the coastal site, but only a small disadvantage at the inland site. The results point out the importance of integrating over several fitness components when documenting the magnitude of local adaptation.

Prognostic Significance of the CD10+CD19+CD34+ B-Progenitor Immunophenotype in Children with Acute Lymphoblastic Leukemia: A Report from the Children's Cancer Group

Leukemic cells from most patients with B-lineage acute lymphoblastic leukemia (ALL) appear to originate from normal B-lymphocyte precursors. The earliest B-cell progenitors co-express the antigens CD10, CD19, or CD34 on their cell surfaces. In a large cohort of 2028 children with ALL, we compared treatment outcomes of a subset of B-lineage ALL patients with CD10+CD19+CD34+ immature B-progenitor leukemia (BPL) to the treatment outcomes of the remaining CD19+ B-lineage ALL patients. Pediatric B-lineage ALL cases enrolled on risk-adjusted ALL treatment protocols of the Children's Cancer Group were immunopheno-typically classified as BPL or non-BPL. Patients were stratified further into age groups of ≥1 year and <12 months. Event-free survival (EFS) outcomes were calculated by standard life table methods. BPL patients in both age groups generally had more favorable presenting characteristics than non-BPL controls. Within the age group of ≥1 year, BPL patients had a slightly better EFS outcome than non-BPL patients, with 3-year estimates of 83.9% (SD = 1.1%) vs. 78.8% (SD = 1.8%), respectively (P = 0.10). Infants with BPL, representing one-fifth of the total infant patient population, had a significantly better EFS outcome than infants with non-BPL (three-year EFS: 82.4%, SD = 9.2% vs. 34.4%, SD = 5.9%, P = 0.006). In univariate analyses, the relative hazard rate (RHR) was 3.73 for non-BPL vs BPL and this marked difference in EFS outcome was maintained at 5 years of follow-up. The favorable prognostic influence of the BPL immunophenotype for infants remained significant in multivariate analyses with an RHR of 2.72 for non-BPL vs BPL (P = 0.05). CD10+CD19+CD34+ immature B-progenitor immunophenotype is associated with favorable characteristics for children with ALL and identifies a subset of infants who achieve favorable EFS outcomes.

Life expectancy biases in clinical decision modeling.

Clinical decision models often rely upon survival models predicated on disease-specific hazard functions combined with baseline hazard functions obtained from standard life tables. Two biases may arise in such a modeling process. First, life expectancy estimates may be biased even if estimates of survival probabilities are unbiased (misestimation bias). In simulation studies, the authors discovered that the magnitude of misestimation bias is larger as life expectancy increases, sample size decreases, and censoring percentage increases. In the context of a simple decision analysis, they found that imbalances in the sample sizes for the data used to estimate the parameters among different strategies resulted in non-optimal decisions in the long run. The second bias stems from misspecification of the survival model itself (misspecification bias). Using a simple cost-effectiveness model, the authors found that life expectancies and incremental cost-effectiveness ratios differed depending on whether an excess-mortality or a proportional-hazards model was specified. In addition, a predictable pattern was observed for these two survival models when extrapolated to other age and gender groups.

Model life table for captive chimpanzees.

Mortality statistics from three captive populations of chimpanzees (Pan troglodytes) were combined to generate standard model life tables for each sex in this species. The model is compared to an estimate of survivorship of a group of wild animals, and is applied to an incomplete data set to illustrate how the model may be used to extend estimates of mortality statistics to missing older ages. © 1995 Wiley-Liss, Inc.

MIAMOD: a computer package to estimate chronic disease morbidity using mortality and survival data

The MIAMOD package is for use in epidemiological analysis of chronic degenerative diseases. The package has been designed to use survival and mortality data supplied by the user, to estimate incidence and prevalence rates, to forecast future mortality and morbidity levels and to provide life tables. Estimates are derived by modelling incidence as an age-period-cohort function and by the equations relating specific cause mortality and prevalence to incidence and survival. The model parameters are evaluated by fitting mortality data by means of a weighted non-linear regression model. Numerical and statistical methods used to solve the regression and to compute standard errors, projections, and life tables are discussed. The program is written in standard FORTRAN 77 and runs on a mainframe computer. The different program units are illustrated together with the principal implementation options. An example of application is provided to show a typical output pattern.

Evaluating a neglected dimension of economic development: Mortality, risk aversion and uncertainty

Mortality and longevity are important but neglected dimensions of economic well-being. This paper develops a general method for applying stochastic dominance ranking procedures to evaluate mortality distributions across populations and among major regions of the world. The dominance approach is shown to have a number of important advantages, which are illustrated with applications using data from standard life tables. The problem of “missing women” is investigated by making dominance comparisons of female mortality distributions among major LDC regions. Using United Nations model life-table data it is shown that for a wide range of life expectancy values, female mortality in the Far East dominates the overall pattern for females in LDCs, while the converse is true for South Asia and Latin America.

Model life tables for the smaller new world monkeys.

Mortality statistics from five populations of small New World monkeys (includinsg Callithrix jaccus, Leontopithecus rosalia, Saguinus fuscicollis, and Saguinus oedipus) were combined to generate a standard model life table reflecting the mortality patterns of these primates. The model is applied to three individual populations to illustrate a strategy for smoothing and interpolating mortality statistics of varying completeness and quality. © 1993 Wiley-Liss, Inc.

The mortality of lead smelter workers: an update.

Mortality studies of lead workers have shown excesses of nonmalignant renal disease and cerebrovascular disease. Animal studies and one human study have shown excess kidney cancer. We have updated a mortality study of male lead smelter workers (n = 1990). An analysis was conducted using standard life table techniques. The updated analysis added 11 years of follow-up and 363 new deaths. The original study had found elevated but nonsignificant risks for kidney cancer, stroke, and nonmalignant renal disease, probably attributable to lead exposure. Deaths from accidents and nonmalignant respiratory disease were significantly elevated, but probably not as a result of lead exposure. In the updated study, no new deaths from nonmalignant renal disease occurred (9 observed, standardized mortality ratio = 1.21). Three more deaths from kidney cancer were observed, yielding a standardized mortality ratio of 1.93 (9 observed, 95% CI = 0.88, 3.67), which increased for those who had worked in areas with the highest lead exposure (8 observed, standardized mortality ratio = 2.39, 95% CI = 1.03, 4.71). Cerebrovascular disease remained elevated for those with more than 20 years of exposure (26 observed, standardized mortality ratio = 1.41, 95% CI = 0.92, 2.07). This cohort with high lead exposure showed a diminishing excess of death from nonmalignant renal disease, a continued excess from kidney cancer, and an excess of cerebrovascular disease only in those with longest exposure to lead.

The standardized mortality ratio and life expectancy.

This paper develops a theoretical relation between the standardized mortality ratio (SMR) and the expected years of life and establishes a regression equation for easy conversion between these two statistics. The mathematical expression of the derived relation is an approximation, requiring an assumption of constant age-specific mortality ratios. It underestimates the "true" value calculated based on life table technique when the age-specific mortality ratios increase with age. This equation provides a conservative method to estimate the expected years of life for cohort mortality studies and facilitates an assessment of the impact of work-related factors on the length of life of the worker. It also allows one to convert the SMR to life expectancy in smaller studies whose sole objective is to determine the SMR in a working population. A 1% decrease (or increase) in the standardized mortality ratio will result in 0.1373 years increased (or decreased) life expectancy based on white male data for the US population. Furthermore, with data from 14 large oil refinery and chemical worker cohorts of white males, the "derived" expected years of life based on the regression equation closely predicts the corresponding value calculated using a standard life table technique. This statistical equation is expected to have practical applications when used in conjunction with the SMR to provide an approximate measure of life expectancy, a term and statistic familiar to most lay people.

A Comparison of Hospital Costs and Morbidity Between Octogenarians and Other Patients Undergoing General Surgical Operations

The hospital costs and clinical results of 304 patients who were more than 80 years old and who underwent general surgical procedures were evaluated. The over-all mortality rate was 14 per cent; 19.9 per cent occurred in patients admitted under emergency conditions as compared with 8.9 per cent that occurred in patients undergoing elective procedures (p less than 0.001). Seventy-nine per cent of the patients were discharged and 7 per cent required care in a skilled nursing facility. Survival rates were as good or better than standard life table survival rates for 80 year old patients. Costs were higher in those who were admitted under emergent conditions or who died in the hospital. Deaths were a result of complications of the primary disease rather than associated disease in most groups. Neither costs nor length of stay could accurately predict survival of individual patients. We concluded that health resources should be directed at treating problems, such as cholelithiasis, hernia or carcinoma, early before complications develop.

Cash Value of the Dairy Cow Predicted from Net Income over Remaining Herd Life

For decisions involving the purchase of dairy cattle, cow cash value can be defined as net income over remaining herd life plus terminal salvage value. Cow net income per month was predicted from income curves, and life expectancy was estimated using standard life table techniques. Estimates of cow net income per month over 13 calvings were calculated for cows with 27 combinations of cow characteristics (including parity, stage of lactation, fertility, producing ability, salvage value, and health problems) in combination with nine milk and feed prices. Remaining herd life was estimated for each cow parity, pregnancy status, and stage of lactation. For each parity, lactation stage, and pregnancy status combination, appropriate estimates of cow net income per month over estimated remaining herd life were discounted to the cow's present age, summed, and added to a terminal cow salvage value. These observations of cow cash value were analyzed by regression analysis. Parity, producing ability, and milk price had the most effect on cash value. Cash value was highest at freshening in second lactation with a consistent pattern of change after calving in all parities. Prediction equations can estimate the maximum price or depreciation for a particular animal and the relative values of different animals.

Mortality of wild and captive chimpanzees.

Mortality of chimpanzees in the wild (Gombe National Park) and in captivity (Taronga Zoo, Sydney and Melbourne Zoo) was compared using standard cohort life table techniques. Overall mortality probabilities up to age 30 were compared using a logrank test. No significant difference in overall mortality was revealed, and the mortality curves did appear to be surprisingly similar, but there were nevertheless some differences in the distribution of mortality. Perinatal mortality was higher in the zoo, while post-perinatal and infant mortality were higher in the wild. Survivorship in the older zoo animals (over age 27) was better than the wild. These differences were attributed to the more sheltered zoo environment, including the availability of veterinary care, which could be expected to improve survival in infants and older adults. The higher perinatal mortality experienced by zoo infants could be reflecting higher levels of inbreeding among the zoo animals.

Evaluation of a simplified method for estimation of early childhood mortality in small populations.

The provision of simple health technologies in less developed countries has far outpaced the capabilities to evaluate their impact on health in general, and early childhood survival in particular. In rural Haiti, attempts to monitor the impact of health care delivery programmes have been frustrated by some of the same problems encountered elsewhere; ie lack of practicable yet scientifically sound methodologies that interface well with ongoing service delivery programmes. The 'preceding birth' technique, originally advanced by Brass and Macrae, holds promise as just such a method. Its practical appeal derives largely from simple data requirements. In its simplest form, the method requires only responses to a single question put to mothers at delivery regarding the survival status of her previous child. They have shown that the proportion of immediately preceding births dying before the 'index' birth date provides a good approximation of the standard life table probability of death before the second birthday. Given that in rural Haiti, as in much of the less developed world, few women deliver in clinic or hospital where such data could be systematically obtained, exploitation of the preceding birth method would require identification of a convenient and unobtrusive point of contact between questioner and mothers who have recently delivered. In Haiti, two options arose: (1) interview women at home after childbirth, and (2) interview women when they bring the 'index' child seeking vaccination or some other child survival intervention. Both of these deviate from the original technique of Brass and Macrae with respect to the timing and method of data collection, and could therefore introduce serious complications to the interpretation of trends in child mortality. To study this, we examined the effects of adapting the preceding birth method to a rural less developed country setting in Mirebalais, where since 1983 primary health care activities have been administered by MARCH (Management and Resources for Community Health), a private voluntary health organization. The Mirebalais study used a pregnancy register, originally developed for targeting of services, to identify women who were expected to have given birth during the 12-month period before each of two survey rounds. Brief interviews with these women would provide direct life table estimates of child mortality level and trend with which to compare estimates produced from use of the preceding birth method in modified form. Direct estimates of the probability of dying before the second birthday were 138/1000 from first round data and 134/1000 from second round data, indicating a 3% decline.(ABSTRACT TRUNCATED AT 400 WORDS)

Model life tables for the larger old world monkeys.

Mortality statistics for 25 populations of the larger Old World monkeys (members of the subfamily Cercopithecinae) were evaluated with a competing hazard model of mortality. The best eight of these life tables were combined to generate a standard model life table representative of the mortality patterns of these primates. Two applications of the standard model to smooth, graduate, and compare life tables based on limited and defective data are presented.

What are the odds that smoking will kill you?

We calculated the long-term risks of death from smoking for individuals of various ages and smoking status in terms of the excess mortality contributed by smoking, over and above the baseline mortality from the same diseases caused by factors other than smoking using standard life table procedures. Since mortality data for specific smoking categories were available only from prospective studies in the late 1950s, we scaled these to the 1982 mortality levels. We assumed, for lung cancer, that the death rates for nonsmokers have not changed and, for other smoking-related diseases, that the risks of death for smokers relative to those for nonsmokers have not changed since the 1950s. Probabilities that result from alternative assumptions were also investigated and are presented. As many as one-third of heavy smokers age 35 will die before age 85 of diseases caused by their smoking. The probabilities of death from smoking when compared with other causes may be persuasive as public education tools. Their effective use for this purpose is affected not only by the deficiencies in the public's factual knowledge of the magnitude of the risks from smoking, but also by numerous apparent misconceptions relating to the interpretation of risk information. Risk data should be presented to the public in a manner that clarifies these misconceptions and facilitates their understanding of the overwhelming risk imposed by smoking.

Factors influencing the age at natural menopause

To examine sociodemographic, menstrual, reproductive, and other factors which may influence the age at natural menopause, the authors analyzed data from a large series of women participating in a nationwide breast cancer screening program conducted between 1973 and 1980. Standard life table techniques permitted assessment of factors suspected of varying the time to menstrual cessation among 983 premenopausal women, 1091 surgically menopausal women, and 1423 naturally menopausal women. The median age at natural menopause was 51.1 years. Multivariate analysis indicated that parity, irregularity of menstrual cycles before age 25 or first livebirth, and high socioeconomic status were significantly related to menopausal age. These data provide evidence for the hypothesis that certain environmental and hormonal factors which affect ovulation during reproductive years may ultimately postpone the menopause.

Fertility and the Development of Agriculture in the Prehistoric Midwest

In this article we develop and apply a method for estimating fertility in paleodemographic study. The proportion D30+/D5+, generated from standard life table calculations, is used to estimate relative fertility rates for eight Woodland and Mississippian populations represented by skeletal series from west-central Illinois. The inferred pattern of fertility increase through time is then considered in the context of key variables that define diet, technology, and sedentism. We conclude that changes in diet or food preparation techniques are implicated in this demographic change. The absence of a significant increment in juvenile mortality in association with the elevated fertility rates suggests that these changes in fertility explain the regional population increase previously inferred from mortuary and habitation site densities.

Applications of the grade of membership technique to event history analysis: Extensions to multivariate unobserved heterogeneity

Analyses of the event histories of social and service utilization processes are often difficult because of a lack of adequate theory to specify the distributional form of any latent heterogeneity [J. Heckman and B. Singer, The identifiability of the proportional hazards model. Rev. Econ. Studies 51 , 231–241 (1984); ibid. , A method for minimizing the impact of distributional assumptions in econometric models for duration data. Econometrics 52 , 271–320 (1984).] or the form of the basic hazard rate [J. Trussel and C. Hammerslough, A hazards-model analysis of the covariates of infant and child mortality in Sri Lanka. Demography 20 , 1–26 (1983).]. In this study we present an analytic strategy that deals with both questions nonparametrically using a conditional likelihood approach. The model is illustrated using 24 months of follow-up data on Supplemental Security Income beneficiaries in Type D (Nursing Home) living arrangements. The parameter estimates can be used in standard life table computations to determine the amount of time expected to be spent in different residential and payment statuses for different analytically identified classes of beneficiaries.

Biogenic grafts in arterial surgery--long-term results (I. The homologous vein--II. The modified heterologous bovine carotid artery--III. The human umbilical vein).

This report summarizes the authors' experience with homologous vein grafts, modified heterologous bovine carotid artery grafts and human umbilical vein grafts in reconstructive vascular surgery. The homologous saphenous vein, taken from living donors, was implanted in 21 patients. The high percentage of early and late complications (28% and 38%, respectively), the difficult availability and the development of modern materials appear to suggest that these grafts, at least the type used in this study, should no longer be employed. The experience with 102 femoro-popliteal and femoro-tibial bypasses in 140 revascularization operations carried out with modified heterologous bovine carotid artery grafts (Solcograft) is presented. The cumulative patency rate was 43% after 5 years for the above-knee and 33% for the below-knee femoro-popliteal bypasses. The high early and late complication rates (37% and 35%) lead us to believe that this graft should also no longer be employed. The human umbilical cord vein (Meadox-Dardik-Biograft) was used in performing 68 femoro-popliteal and 15 femoro-crural bypasses in 60 limbs of 57 patients. The patency rates calculated according to the standard life table method was 36% for the above-knee (after 5 years) and 32% for the below-knee femoro-popliteal bypass (after 4 years) and 31% (after 3 years) for the femoro-tibial bypass, respectively. On the understanding that other materials should be preferred in the individual case, this material still seems to be recommendable as a graft of second or third choice.

Risk factors in schizophrenia: season birth in Maryland, USA.

The association between the risk for schizophrenia and season of birth was studied using a standard actuarial life table method. This method of analysis eliminates the possibility of the previously described statistical artifacts from the data. An increased risk for schizophrenia for winter born individuals was demonstrated. The analysis also supported the hypothesis that season of birth is associated with an increased risk for a subtype of schizophrenia.