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PubMed1984

The uses and abuses of life-table methods in vascular surgery.

This paper details the calculations involved in a life-table analysis and appraises the current use of this technique in vascular research. We suggest that the presentation of patency curves should be standardized and recommend that: curves are presented as step rather than continuous graphs; the number of patients remaining in a study are shown at intervals along patency curves; the length of time for which a curve is claimed to hold is more rigorously defined; an attempt is made to increase, where possible, the frequency of patient review, particularly in the immediate postoperative period; ways of increasing the total sample size (e.g. multicentre studies) are investigated. We also recommend that a set of definitive guidelines on the presentation of graft patency data acceptable to all the major vascular journals be sought.

Actuarial Analysis↗
PubMed1982

A modified life table method to study congenital genetic disorders: an application in sickle cell anemia.

A modified life table procedure is introduced designed to study the survival of patients with congenital genetic disorders with the endpoint defined by a complication or death. It uses the ages of the patients as the time axis as in "population' or "current' life tables, and it allows patients to enter and exit the study as in survival life tables. The procedure uses the exact length of time that each patient is observed in the study to determine the conditional probabilities of developing the complication. The proposed procedure is especially helpful in studying recurrent complications or events that occur frequently. The proposed life table procedure is demonstrated in the study of the conditional probability of developing a sickle cell crisis in 509 patients with sickle cell anemia (SS) with different number of prior crises. The demonstration is intended to illustrate the use of the proposed method and not to investigate the clinical severity of sickle cell anemia. It was found that the risk of crisis was to investigate the clinical severity of sickle cell anemia. It was found that the risk of crisis was positively related to the number of prior crises in SS patients (P less than 0.001). This trend was significant in the first three decades of life.

Actuarial Analysis↗
PubMed1987

Analysis of underlying and multiple-cause mortality data: the life table methods.

The stochastic compartment model concepts are employed to analyse and construct complete and abbreviated total mortality life tables, multiple-decrement life tables for a disease, under the underlying and pattern-of-failure definitions of mortality risk, cause-elimination life tables, cause-elimination effects on saved population through the gain in life expectancy as a consequence of eliminating the mortality risk, cause-delay life tables designed to translate the clinically observed increase in survival time as the population gain in life expectancy that would occur if a treatment protocol was made available to the general population and life tables for disease dependency in multiple-cause data.

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↗
PubMed1987

Comparison of risk estimates using life-table methods.

Risk estimates promulgated by various radiation protection authorities in recent years have become increasingly more complex. Early "integral" estimates in the form of health effects per 0.01 person-Gy (per person-rad) or per 10(4) person-Gy (per 10(6) person-rad) have tended to be replaced by "differential" estimates which are age- and sex-dependent and specify both minimum induction (latency) and duration of risk expression (plateau) periods. These latter types of risk estimate must be used in conjunction with a life table in order to reduce them to integral form. In this paper, the life table has been used to effect a comparison of the organ and tissue risk estimates derived in several recent reports. In addition, a brief review of life-table methodology is presented and some features of the models used in deriving differential coefficients are discussed. While the great number of permutations possible with dose-response models, detailed risk estimates and proposed projection models precludes any unique result, the reduced integral coefficients are required to conform to the linear, absolute-risk model recommended for use with the integral risk estimates reviewed.

Actuarial Analysis↗
PubMed1967

Epidemiological basis of tuberculosis eradication. 7. Application of life-table methods for assessing the prognosis for tuberculosis patients.

The experience of a group of patients, observed in a follow-up study, may conveniently be described by means of decrement tables, of which the survival table is the best known. Just as this table shows how a population group has decreased gradually because of death, so other decrement tables may depict the cumulative effect of cure, or of death and cure combined.Decrement tables can be established not only when all patients under study have been observed from the onset of their disease until cure or death, but also when patients with varying durations of disease have been followed for only a few years; in this case the statistical technique used for the construction of life-tables must be applied.This paper demonstrates in detail the tabulations and calculations involved in this technique, using nationwide data from the Danish Tuberculosis Register as the basis, and applying the technique to aspects of the prognosis for tuberculosis patients that have hitherto been difficult to quantify.

Denmark↗
PubMed1993

[Analysis of the effect of PC-IOL implantation on intraocular pressure control in glaucoma eyes using the life-table method].

Cataract extraction and posterior chamber intraocular lens (PC-IOL) implantation were carried out in 21 primary angle glaucoma (POAG) and 26 primary angle closure glaucoma (PACG) eyes in which preoperative intraocular pressure (IOP) was well controlled with medication. The postoperative IOP on the first postoperative day was significantly higher than the preoperative level in POAG eyes, while no significant difference was seen in PACG eyes. The postoperative IOP was significantly lower than the preoperative level at 3 and 6 months postoperatively in POAG eyes and at 1-12 months postoperatively in PACG eyes. Medication did not differ significantly pre- and postoperatively. In 64 +/- 11% (SE) of POAG and 63 +/- 15% of PACG the status of IOP control did not worsen at 2 years. Overall, 70% of the eyes the status of IOP control improved postoperatively, and this was maintained for 2 years in 44 +/- 12%. The present result implies that in primary glaucoma, PC-IOL implantation surgery does not need to be combined with glaucoma surgeries when the IOP was satisfactory controlled and the stage of disease was not advanced.

Female↗
PubMedDate not supplied

[Comments on the use of the "life-table method" in orthopedics].

In the description of long term results, e.g. of joint replacements, survivorship analysis is used increasingly in orthopaedic surgery. The survivorship analysis is more useful to describe the frequency of failure rather than global statements in percentage. The relative probability of failure for fixed intervals is drawn from the number of controlled patients and the frequency of failure. The complementary probabilities of success are linked in their temporal sequence thus representing the probability of survival at a fixed endpoint. Necessary condition for the use of this procedure is the exact definition of moment and manner of failure. It is described how to establish survivorship tables.

Follow-Up Studies↗
PubMed1983

Life-table methods for evaluating antiarrhythmic drug efficacy in patients with paroxysmal atrial tachycardia.

Spontaneous variability in the occurrence of paroxysmal arrhythmias has made it difficult to apply objective and quantitative methods to describe their clinical course. In this study of paroxysmal atrial tachycardia, the "tachycardia-free interval" was used as a quantitative measure of drug efficacy during treatment with oral verapamil. The tachycardia-free interval is the time a patient remains free from an episode of tachycardia after drug treatment is begun. We documented recurrent tachycardia by telephone transmission of the electrocardiogram. Improvement caused by increasing the drug dose (360 versus 480 mg/day) or by comparing verapamil with placebo treatment was demonstrated by upward shifts in the cumulative tachycardia-free interval curves. The tachycardia-free interval is an easily measured clinical variable that has substantial promise in the study of paroxysmal arrhythmias.

Actuarial Analysis↗
PubMed1986

Analysis of survival data using the actuarial life table method.

A microcomputer program has been developed for an Apple II Plus microcomputer for the analysis of survival data. The program is fully interactive and can analyze complete survival and censored data. Input to the program may be in the form of frequency data or individual patient information. Standard errors of the cumulative survival function are also computed using Greenwood's formula. Incorrectly specified data can be modified immediately with little effort from the user.

Actuarial Analysis↗
PubMed1984

Relapse in affective disorders: a reanalysis of the literature using life table methods.

Using survival methods the authors review and reanalyze nine published reports on relapse after recovery from depression. Despite wide disagreement over cross-sectional rates of relapse, the reanalysis reveals a common finding that the hazard of relapse declines steadily for the first three years after recovery. Methodological and design issues are discussed and summarized for the 40 naturalistic studies that report on longitudinal outcome after recovery from depression. The principles and techniques of survival methods are briefly introduced in an Appendix.

Actuarial Analysis↗
PubMed1984

Life table methods for assessing the dynamics of U.S. nursing home utilization: 1976-1977.

One likely consequence of the aging of the U.S. population is the growth of the number of persons in nursing homes. As the numbers of persons in nursing homes increase so will the amount of resources required to keep them in those homes. This will make it increasingly important to understand the dynamics of nursing home utilization so that we can more effectively plan the allocation of resources. Unfortunately, we lack direct information on the dynamics of nursing home utilization both because of the expense of implementing longitudinal studies to gather such information and because the available data on current residents are inappropriate to study the dynamics of utilization because of several types of bias. Demographic methods are presented that can be applied to survey data to remove sample biases from the data and permit study of the dynamics of the utilization of facilities for the total U.S. nursing home population and for various of its components.

Actuarial Analysis↗