Name: life table method for survival rates
Uploaded: 2025-01-09T15:14:16.000Z
Duration: 1 min 20 s
Channel: JoVE

A análise de sobrevida avalia o tempo até que ocorra um evento como morte ou falha do tratamento. A abordagem atuarial ou da tabela de vida, adaptada da ciência atuarial, analisa os dados de sobrevivência.
Em um cenário de estudo clínico, os participantes são divididos em grupos com diferentes durações de acompanhamento para se concentrar em períodos críticos, como o primeiro ano após a cirurgia de alto risco.
O método atuarial calcula as taxas de sobrevida em intervalos predeterminados, utilizando totalmente os dados de todos os participantes, incluindo aqueles que perderam o acompanhamento ou que morreram por outras causas.
Para entender o impacto na sobrevida do primeiro ano, as taxas de sobrevida de um ano são derivadas subtraindo o número de mortes do total de participantes e dividindo pelo número original.
Apenas o subconjunto de pacientes observados durante os dois anos completos é considerado para estimar a sobrevida em dois anos, com foco naqueles que sobreviveram ao primeiro ano e continuaram a sobreviver ao segundo ano.
Esse método é consistente, ajuda a identificar tendências de longo prazo e avalia a eficácia de tratamentos ou intervenções, fornecendo uma ferramenta robusta para entender os resultados da pesquisa médica.

avaliação atuarial

Actuarial Approach

A abordagem atuarial, um método estatístico originalmente desenvolvido para avaliação de risco de seguro de vida, é amplamente usada para calcular taxas de sobrevivência em estudos clínicos e populacionais. Este método considera os participantes perdidos no acompanhamento ou aqueles que morrem por causas não relacionadas ao estudo, garantindo uma representação mais precisa das probabilidades de sobrevivência. Considere o exemplo de um procedimento cirúrgico de alto risco com mortalidade significativa em estágio inicial. Um estudo clínico de dois anos é conduzido, com foco no primeiro ano crítico. Os participantes são divididos em dois grupos: um acompanhado por um ano e outro por dois anos. As taxas de sobrevivência são estimadas usando o método atuarial (ou tábua de vida), que divide o período do estudo em intervalos — normalmente um ano. Para ilustrar, suponha que o primeiro grupo comece com 1.000 pacientes, dos quais 240 morrem no primeiro ano. O segundo grupo também começa com 1.000 pacientes, com 200 mortes no primeiro ano e 16 no segundo ano. A taxa de sobrevivência de um ano é calculada subtraindo o número total de mortes do tamanho inicial da coorte e dividindo o resultado pela população inicial: Taxa de sobrevivência de um ano = (2000−240−200)/2000=0,78 ou 78% Essa abordagem também pode ser aplicada a estudos de resultados de longo prazo, como avaliar a eficácia de um tratamento de câncer ao longo dos anos. O método atuarial acomoda pacientes perdidos no acompanhamento ou que morrem de causas não relacionadas, permitindo uma análise robusta dos efeitos de longo prazo. Para taxas de sobrevivência de dois anos, o cálculo se torna mais sutil. Ele usa probabilidade condicional, considerando apenas os indivíduos observados durante os dois anos completos e que sobreviveram ao primeiro ano. A taxa de sobrevivência de dois anos não deve exceder a taxa de um ano e é determinada multiplicando a probabilidade de sobreviver ao primeiro ano pela probabilidade de sobreviver ao segundo ano, condicional à sobrevivência ao primeiro ano: Taxa de sobrevivência de dois anos = 0,78 × 0,98 = 0,7644 ou 76,44% Este método sofisticado, embora poderoso, enfrenta desafios como dados de acompanhamento incompletos e o registro preciso de mortes. Apesar dessas limitações, ele continua particularmente eficaz em estudos populacionais em larga escala, onde o rastreamento de participantes individuais é impraticável. Ao contabilizar a censura e as probabilidades de sobrevivência baseadas em intervalos, a abordagem atuarial fornece uma estrutura confiável para a análise de sobrevivência em diversos contextos de pesquisa.

Avaliação Atuarial

A análise de sobrevida avalia o tempo até que ocorra um evento como morte ou falha do tratamento. A abordagem atuarial ou da tábua de vida, adaptada da abordagem atuarial ...

Education

JoVE Core

Statistics

Estatísticas

Unit 1

Unidade 1

Survival Analysis

Análise de Sobrevivência

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

life table method for survival rates

The life table method, also called the actuarial approach, is used to estimate survival rates in clinical and population studies. It began in life insurance, where risk over time must be measured carefully. In health research, it gives a clearer picture of survival when some participants are lost to follow-up or die from causes unrelated to the study.

This method works by dividing the study period into set intervals, usually one year. That makes it useful for tracking outcomes over time, especially in studies with early deaths after a high-risk surgical procedure. In one example, a two-year study follows two groups. One group is observed for one year, and the other is observed for two years.

The one-year survival rate is found from the starting group size and the number of deaths during that year. In the example, 1,000 patients begin in each group. The first group has 240 deaths in the first year, and the second group has 200 deaths in the first year. Using the actuarial calculation, the one-year survival rate is 78%.

The same method can also be used for long-term studies, such as testing how well a cancer treatment works over several years. It accounts for patients who are not followed for the full study or who die from unrelated causes. That makes the survival estimate more realistic when individual tracking is difficult.

Two-year survival uses conditional probability, which means the second year is calculated only for people who survived the first year and were observed for the full two years. In the example, the second-year survival probability is multiplied by the first-year survival probability. The result is 0.78 times 0.98, or 76.44%.

A two-year survival rate should not be higher than the one-year rate. The method is powerful, but it depends on complete follow-up and accurate death records. Even with those limits, it is especially useful in large population studies where following each person closely is not practical.

Life Table Method for Survival Rates

introduction to survival analysis

Time-to-Event Data and Censoring

Survival analysis is a statistical method for time-to-event data. The event can be death, disease relapse, system failure, or recovery. It helps estimate survival time, which is the time until a specific event occurs, and it also shows what factors may affect that time. A key idea in survival analysis is censoring. Censoring happens when the event of interest has not been observed for some people during the study period. Because the data are incomplete in those cases, survival analysis uses...

life tables

Life Tables and Survival Patterns

A life table is a statistical tool that shows mortality and survival patterns in a population. It organizes data across age intervals so students can see how likely a group is to survive or die at each stage of life. The table gives a clear snapshot of population dynamics over time. Life tables are used in demography, public health, actuarial science, and ecology. They help scientists study life expectancy, plan health interventions, estimate insurance risk, and compare how species survive in...

survival curves

Kaplan-Meier Survival Curve Basics

Kaplan-Meier survival curves show how the chance of staying event-free changes over time. They are used to track survival in a population and to compare groups in medicine, public health, and reliability engineering. The Kaplan-Meier estimator is the most common way to build these curves. It is a non-parametric method, which means it does not assume a fixed pattern for the data. The result is a stepwise line that drops each time an event happens, such as death, disease recurrence, or...

actuarial approach

The life table method, also called the actuarial approach, is used to estimate survival rates in clinical and population studies. It began in life insurance, where risk over time must be measured carefully. In health research, it gives a clearer picture of survival when some participants are lost to follow-up or die from causes unrelated to the study. This method works by dividing the study period into set intervals, usually one year. That makes it useful for tracking outcomes over time,...

kaplan-meier approach

Survival Curves with Kaplan-Meier Data

The Kaplan-Meier estimator is a non-parametric method for estimating a survival function from time-to-event data. It is commonly used in medical research to track how many patients survive for a set time after treatment. It is also important in clinical trials, epidemiological studies, and reliability engineering. This method helps researchers study survival probabilities over time, even when some data are incomplete. That incomplete data is called censored data, which means the exact event...

assumptions of survival analysis

Survival Analysis Assumptions in Studies

Survival analysis studies the time until an event happens. The event may be death in a living organism or failure in a mechanical system. These models are used in medicine, biology, engineering, and public health to study time-to-event data. Careful study design matters because the method depends on several key assumptions. One common feature of survival times is positive skewness. This means events often happen early, while fewer cases occur later. Survival data also often include censoring,...

comparing the survival analysis of two or more groups

comparing-the-survival-analysis-of-two-or-more-groups

Kaplan-Meier Curves and Hazard Ratios

Kaplan-Meier curves and hazard ratios help researchers compare survival time between groups. Survival analysis looks at the time until an event happens, such as death, disease recurrence, or recovery. It is a key tool in medical research. A major strength of survival analysis is that it can handle censored data. Censored data means the event has not happened for some participants by the end of the study, or it has not been observed. This makes survival analysis different from standard...

the mantel-cox log-rank test

Log-Rank Test for Comparing Survival Curves

The Mantel-Cox log-rank test compares survival curves from two groups. It checks whether the groups have a statistically significant difference in survival time. This makes it useful when the timing of an event matters, such as death or disease recurrence. The log-rank test is non-parametric. That means it does not assume a specific distribution for the survival data. It is also useful in medical research, where it often helps compare a new treatment with a control or standard treatment in...

applications of life tables

Life Tables in Public Policy and Science

Life tables are used in many fields to study mortality and survival rates. They give a numerical way to examine how long people or living things are likely to survive. This makes them useful for public health, business planning, and scientific research. In demography and public health, life tables help experts study population changes and predict future trends. They can show patterns such as an aging population or the effect of a health policy. In Nigeria, health officials used survival rates...

cancer survival analysis

Cancer Survival Curves and Risk Factors

Cancer survival analysis measures how long it takes from diagnosis or the start of treatment to a specific outcome, such as remission or death. It helps researchers judge treatment effectiveness and understand what affects patient outcomes. These results also support clinical decisions and prognostic evaluations. Survival data are often skewed and not normally distributed. They also include censored cases, where the full survival time is unknown because the study ends, a patient is lost to...

hazard rate

Modeling Event Risk Over Time

Hazard rate is a statistical measure that describes how event risk changes over time. It is also called the hazard function or failure rate. In survival analysis, it shows the instantaneous rate at which an event occurs, but only after the subject has not had the event yet. From a probability view, hazard rate gives the chance that a subject will have the event in a very small time interval. That chance is conditional on surviving to the start of that interval. From a frequency view, it can...

hazard ratio

Hazard Ratio in Clinical Trials

The hazard ratio is a way to compare event risk in clinical trials. It is often used to study events such as death or disease recurrence in two groups over time. The two groups are usually a treatment group and a control group. A hazard ratio compares hazard rates, which are the instantaneous risk of an event happening at a given moment. It shows how the risk in one group relates to the risk in the other group. In a cancer drug study, for example, the hazard ratio can show how a new treatment...

truncation in survival analysis

Left and Right Truncation in Survival Data

Truncation in survival analysis describes data loss caused by the timing of an event or by when a subject can enter a study. It can happen in two forms: left truncation and right truncation. In both cases, some individuals are left out of the dataset before analysis begins. Left truncation happens when people who had the event before a set time are not included in the study. This often occurs with delayed entry, which means a person is only observed if they survive until the entry point. For...

censoring survival data

Types of Censoring in Survival Analysis

Survival analysis studies time-to-event data, which tracks how long it takes for an outcome to happen. It is used in medicine, engineering, and social science. A common problem in this type of data is censoring, which means the full event time is not observed for every person or item. Censoring can happen for several reasons and in different patterns. The most common kind is right censoring. This happens when the event has not occurred by the end of the study or when a participant is lost to...

survival tree

Survival Tree in Time-to-Event Analysis

A survival tree is a non-parametric tool in survival analysis that links predictor variables, or covariates, to survival time. Survival time is the time until an event of interest occurs. It is useful when some data are censored, which means the event has not happened for some people by the end of the study or the exact event time is unknown. Building a survival tree starts with a dataset that includes covariates, survival time, and a censoring indicator for each subject. The data must be...

parametric survival analysis: weibull and exponential methods

parametric-survival-analysis-weibull-and-exponential-methods

Modeling Survival Time with Weibull and Exponential

Parametric survival analysis models survival time by assuming a specific probability distribution for when an event occurs. The Weibull and exponential distributions are two common choices because they are flexible and relatively straightforward to use. The Weibull distribution is a flexible model in parametric survival analysis. It can describe both increasing and decreasing hazard rates, depending on its shape parameter beta. When beta is greater than 1, the hazard rate rises over time. That...

key terms and concepts

Learn how the life table method, or actuarial approach, estimates one-year and two-year survival rates while accounting for follow-up losses and unrelated deaths.

Life Table Method for Survival Rates | JoVE K12

statistics

JoVE Core Estatística apresenta os conceitos e aplicação da coleta, análise, apresentação e interpretação de dados para os alunos. Esses vídeos de animação fornecem uma compreensão de estatística beneficial para alunos de uma ampla gama de disciplinas. Além disso, os vídeos do cientista em ação demonstram a aplicação de conceitos relacionados em experimentos de pesquisa clássicos e originais realizados nos laboratórios atuais em todo o mundo.

Life Table Method for Survival Rates

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