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PubMed1987

Dental restoration longevity: a critique of the life table method of analysis.

The use of the life table method for assessing the longevity of dental restorations is growing. One reason for this is the availability of statistical computer packages which can be used by the non-expert, and this is tending to lead to an uncritical approach to the methodology. Although much can be learnt regarding the durability of restorations by using life table analysis, there are many inherent problems related to its use in dental studies. The survival pattern of many restorations is such that long-term studies are required to obtain valid assessments of durability. Results reported after only a few years of study contain many restorations not followed to failure. The ways in which data on these restorations are handled can greatly affect the estimates of longevity. These considerations have not, to date, received sufficient attention.

Actuarial Analysis↗
PubMed1986

Life-table methods for detecting age-risk factor interactions in long-term follow-up studies.

Methodological investigation has suggested that age-risk factor interactions should be more evident in age of experience life tables than in follow-up time tables due to the mixing of ages of experience over follow-up time in groups defined by age at initial examination. To illustrate the two approaches, age modification of the effect of total cholesterol on ischemic heart disease mortality in two long-term follow-up studies was investigated. Follow-up time life table analysis of 116 deaths over 20 years in one study was more consistent with a uniform relative risk due to cholesterol, while age of experience life table analysis was more consistent with a monotonic negative age interaction. In a second follow-up study (160 deaths over 24 years), there was no evidence of a monotonic negative age-cholesterol interaction by either method. It was concluded that age-specific life table analysis should be used when age-risk factor interactions are considered, but that both approaches yield almost identical results in absence of age interaction. The identification of the more appropriate life-table analysis should be ultimately guided by the nature of the age or time phenomena of scientific interest.

Actuarial Analysis↗
PubMed2003

Population-level responses to long-term cadmium exposure in two strains of the freshwater gastropod Biomphalaria glabrata: results from a life-table response experiment.

A life-table response experiment was conducted to ascertain the demographic effects of low-level cadmium exposure on two strains, BS90 and NMRI, of the freshwater gastropod Biomphalaria glabrata. Snails were exposed to cadmium continuously from the embryonic stage through adulthood. Results indicated that cadmium significantly affected a number of individual-based parameters, including %hatch, juvenile survival, and adult survival in both strains. Also, fecundity and time to maturity were significantly affected in the NMRI strain. A stage-based, deterministic, population model indicated that population growth rate (lambda) was significantly affected by cadmium. Elasticity analysis indicated that juvenile survival, in general, had the greatest contribution to lambda. Decomposition analysis indicated that the effects of cadmium on the juvenile stage in BS90 and the embryonic stage in NMRI contributed most to cadmium-induced changes in lambda. The BS90 strain was more sensitive to cadmium toxicity than NMRI. Moreover, the two strains differed in pattern of response with different aspects of their respective life histories contributing to cadmium-induced changes in lambda. Comparisons were also made between the main model, based on a Z transformation of the life-cycle graph, and more commonly used matrix models.

Animals↗
PubMed1982

Relapse in major depressive disorder: analysis with the life table.

With the use of life tables to describe time while patients were well and subsequent rates of relapse for 75 patients after their recovery from an episodes of major depressive disorder in naturalistic study, a high risk of relapse was detected shortly after recovery. Twenty-four percent of patients relapsed within 12 weeks at risk, and 12% of patients relapsed with four weeks at risk. The presence of an underlying chronic depression and three or more previous affective episodes predicted a statistically significant increase in the rate of relapse. These data were used to develop an exponential model of relapse probability for a subgroup of the study population.

Actuarial Analysis↗
PubMed2003

[Construction and important factors analysis of natural life table of diamonthback moth, Plutella xylostella under pesticides treatment].

The natural life tables of diamonthback moth (DBM), Plutella xylostella under pesticides treatment were constructed, and the construction method of item "pesticide" was particularly discussed. The life tables indicated that the indices of population trend (I) under the treatment with 80% Dichlorvos EC 1000x and the contrast were 0.7796 and 1.4804, respectively, showing that Dichlorvos had some control on DBM. But, Dichlorvos had some effects on natural enemies of DBM. The decrease of parasitism rate at pupa stage was most obvious, which indicated that Dichlorvos had some effects of killing and wounding on the natural enemies of DBM.

Animals↗
PubMed1979

A computer program for life table regression analysis with time dependent covariates.

This paper presents a computer program for analyzing time-dependent covariables in survival studies by the life table regression model described by Holford [3]. Basically, life table regression incorporates the elements of regression and the life table into a single model. Regression parameters are estimated by the method of maximum likelihood using the Newton-Raphson iterative procedure. The program provides two methods for testing hypotheses concerning regression coefficients, namely the standard normal deviate test and a Wald statistic based on the first and second derivatives of the log likelihood. Residual plots are provided to assess the fit of the model to the data.

Actuarial Analysis↗
PubMed1989

On the derivation of a full life table from mortality data recorded in five-year age groups.

Mortality data are often gathered using 5-year age groups rather than individual years of life. Furthermore, it is common practice to use a large open-ended interval (such as 85 and over) for mortality data at the older ages. These limitations of the data pose problems for the actuary or demographer who wishes to compile a full and accurate life table using individual years of life. The author devises formulae which handle these problems. He also devises methods for handling mortality during the 1st year of life and for dealing with other technical problems which arise in the compilation of the full life table from grouped data.

Adult↗
PubMed2002

Determining demographic effects of cypermethrin in the marine copepod Acartia tonsa: stage-specific short tests versus life-table tests.

Short-term lethal and sublethal responses of the calanoid copepod Acartia tonsa to cypermethrin were compared with life-table responses to assess whether or not it is necessary to use exposure periods longer than 5 days to estimate demographic responses to stress. More specifically, by limiting exposure periods to sensitive age classes (eggs, nauplii, copepodids, and adults) and including measurements on survival, egg production, and feeding rates, it was possible to derive a short test design of similar sensitivity and ecological relevance as full life-table tests. Short-term exposures to cypermethrin reduced copepodid's feeding rates at concentrations well below those affecting egg production rates and survival of eggs and adult stages. Lethal effects on naupliar stages occurred at lower concentrations than any other effect observed on eggs and adults. Life-table sensitivities of the intrinsic rate of increase ( r(m)) to cypermethrin were similar to those observed in short-term exposures. More specifically, exposure to cypermethrin impaired r(m) responses at concentrations (7.4 ng x L(-1)) that also affected feeding and naupliar responses. Our results show that by quantifying and separating combined toxic effects on ecologically relevant individual life-history traits, it is possible to develop toxicity test designs of similar ecological relevance yet that are less labor-intensive and costly than existing demographic tests.

Animals↗
PubMed1990

Reconstruction of Indian life tables for 1901-1981 and projections for 1981-2001.

"An attempt has been made to reconstruct life tables for India from 1901-11 to 1971-81 and to project for the decades 1981-91 and 1991-2001 by adopting a Brass relational model. The earlier actuarial life tables seem to have been based on a British model of sex differentials in mortality leading to higher life expectancies for females--not in tune with Indian experience. Consistency has been attained in this study by taking recourse to mortality patterns obtained from the Sample Registration System."

Asia↗
PubMed1995

Life table analysis for areas using vital register data.

"This study considers the utility of parameterised life tables derived by survival analysis for comparing mortality between areas, using death registration records and accompanying information on the social characteristics for each individual deceased. Such methods enable a comparison of summary measures of mortality experience such as life expectancy and median age at death before and after adjustment for socio-economic variables. In the absence of comparable information on the survivor population an approximate life table method is investigated as a means of comparing mortality profiles and the effects of social factors. Such factors may pertain both to the individuals (e.g. their birthplace) or to their small area of residence (e.g. measures of area deprivation). These methods also permit a comparison of the impact of socio-economic factors on different causes of death. The application is to mortality in London over the period 1990-92 and to its constituent boroughs and electoral wards."

Cause of Death↗
PubMed1988

The multistate life table with duration-dependence.

"A method for generalizing the multistate, or increment-decrement, life table to include rates which depend upon duration of exposure to risk, as well as upon age, is proposed. The method is built upon the linear approximation, called the linear integration hypothesis, developed mainly by Rogers and his colleagues.... It is possible to derive several new summary indices of the life-table cohort's history, such as the mean and median time in current status, at any age. The method is illustrated using a simple four-state marital-status model which has appeared often in the literature; here, rates of divorce and widowhood vary by duration of marriage as well as age." An example is demonstrated using 1984 period data for women in Finland aged 15-50. (SUMMARY IN FRE)

Age Factors↗
PubMed1995

Formulas expressing life expectancy, survival probability and death rate in life table at various ages in US adults.

The National Center for Health Statistics (Monthly Vital Statistics Report, 41 (1993) 1-36; Pediatrics, 92 (1993) 743-754) reported the life table for the total population of the United States, 1992, on the basis of vital statistics. The life table shows life expectancy, survival and death rate at various ages. Formulas expressing death rate, survival probability and life expectancy at various ages in US adults are constructed from the data of the National Center for Health Statistics (NCHS). A mathematical model of the 'probacent'-probability equation previously published by the author is employed in this study. Analysis of the computer-assisted predicted values and the data reported by the NCHS indicates that the formulas are accurate and reliable with a close agreement in expressing death rate, survival probability and life expectancy at various ages in US adults of 25 years of age and older. The formulas can determine the relationship between the age and the death rate, the survival probability or the life expectancy and may be of value for epidemiologic evaluation of US adults.

Adult↗
PubMed2003

On the analysis of quasi-life tables.

Baxter (1994) defined a quasi-life table in which the data arise from many concurrent, independent, discrete-time renewal processes. The processes are not observed individually, only the total numbers of renewals at each time point are observed. The estimates proposed by Baxter (1994), based on the discrete-time renewal equation, are studied more formally here, and some extensions are made.

Cohort Studies↗
PubMedDate not supplied

Sex-specific life table aging rates in large medfly cohorts.

Life table aging rate (LAR) is defined as the age-specific rate of mortality change with age and corresponds to the first derivative or slope of the mortality schedule at each age. We computed the sex-specific LARs for 167 Medfly cohorts, containing a total of approximately 600,000 individuals of each sex. We found that: (a) the LAR is not constant for either sex; at the youngest ages, mortality changes by approximately 1.4-fold daily, whereas at the older ages (>30 days), mortality levels off and decreases; (b) female LAR is higher than male LAR from 0 to 12 days, at which time the rates cross over and male LAR is higher than female LAR; however, at about 30 days, both male and female LARs are less than or equal to unity; (c) mortality in each of the 167 cohorts leveled off for both sexes. The average age for this leveling off was around 23 days for females and 31 days for males; and (d) the mortality rate at the age of leveling off was approximately 1.4-fold higher in males than in females--0.13/day for females and 0.19/day for males. Implications of these findings are briefly discusses, including the use of summary measures of senescence, the arbitrariness of selecting the age of senescence onset, and test of hypotheses concerned with explanations of mortality patterns such as leveling off at older ages.

Aging↗
PubMedDate not supplied

Effects of environmental temperature on life tables of Rhodnius neivai Lent, 1953 (Hemiptera: Reduviidae) under experimental conditions.

Changes in life tables of Rhodnius neivai due to variations of environmental temperature were studied, based on nine cohorts. Three cohorts were kept at 22 degrees C, three at 27 degrees C and three at 32 degrees C. Cohorts were censused daily during nymphal instars and weekly in adults. Nine complete horizontal life tables were built. A high negative correlation between temperature and age at first laying was registered (r=-0,84). Age at maximum reproduction was significantly lower at 32 degrees C. Average number of eggs/female/week and total eggs/female on its life time were significantly lower at 22 degrees C. Total number of egg by cohort and total number of reproductive weeks were significantly higher at 27 degrees C. At 32 degrees C, generational time was significantly lower. At 27 degrees C net reproductive rate and total reproductive value were significantly higher. At 22 degrees C, intrinsic growth, finite growth and finite birth rates were significantly lower. At 22 degrees C, death instantaneous rate was significantly higher.

Animals↗
PubMed2004

Providing more up-to-date estimates of patient survival: a comparison of standard survival analysis with period analysis using life-table methods and proportional hazards models.

OBJECTIVE: Standard survival methods can yield out-of-date estimates of long-term survival. Period analysis, based on life-table methodology, provides more up-to-date survival estimates by exploring survival during a restricted recent period of interest. It excludes the short-term survival of patients recruited at the start of the study. We use statistical models to further develop the method of period analysis, providing more up-to-date estimates of survival and the ability to explore differences in survival by covariates and adjust for case mix. METHODS: We use cancer registry data for colorectal cancer in Leicestershire, UK, to illustrate the use of Cox proportional hazards (CPH) models to estimate period and standard survival. We compare these estimates with those obtained using life-table methodology. RESULTS: Period estimates were slightly higher than the standard estimates as they reflect recent improvements in short-term survival. The results for period analysis using the life-table approach and using CPH models were similar. However, CPH models allowed further investigation of other risk factors and the ability to control for potential confounding variables. CONCLUSION: Using period survival estimates, more up-to-date information is available to clinicians and others with an interest in monitoring survival. Period CHP models offer all the advantages of statistical modeling, and are straightforward to fit in standard statistical packages.

Colorectal Neoplasms↗
PubMed1994

Complete life tables of Israel, 1988-1992.

"This publication presents complete life tables for [Israel for] 1988-1992. In the tables data are detailed by single ages, for males and females separately. The data are presented for the entire population and for Jews and Non-Jews separately."

Age Factors↗
PubMed1993

Complete life tables of Israel, 1987-1991.

"This publication presents complete life tables [for Israel] for 1987-1991. Data are detailed by single ages, for males and females separately. The data are presented for the entire population and for Jews and Non-Jews separately."

Age Factors↗