Which statement best describes life tables in survival analysis?

• A. They provide prognosis by using observed survival over time and yield interval-specific and cumulative survival probabilities.
• B. They are used to estimate disease incidence from cross-sectional data.
• C. They calculate mortality rates solely from birth data.
• D. They are only applicable to nonhuman populations.

Answer: (B)

The main idea is that life tables summarize how a group survives over time by organizing follow-up into time intervals and estimating the probability of surviving each interval as well as the overall, or cumulative, probability of survival. They use information on how many people are at risk at the start of each interval, how many die during the interval, and how many are censored, to produce interval-specific survival probabilities and a survival curve for the whole follow-up period. This makes life tables useful for describing prognosis and comparing survival between groups, and they can be constructed from cohort or longitudinal data while properly handling censored observations. Life tables are not about estimating disease incidence from cross-sectional data, which relies on different data and methods; they describe survival, not incidence. They are applicable to human populations as well as animal studies, so their scope is broader than nonhuman-only use.