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PubMed1994

On the analysis of life tables for dependent observations.

Applying methods assuming independence when observations are positively correlated means that confidence intervals become too short and significance levels of statistical tests are less extreme. This paper discusses elements of life-table analysis based on the standard product-limit estimator and a modified Greenwood formula for its variance to be used for dependent observations. An application from oral surgery is given. Erroneously assuming independence in the analysis of a life table could have serious consequences. It is demonstrated in a simulation study that the confidence levels can be much too low. The proposed modification of the Greenwood formula for the variance of the estimated survival function most often results in confidence levels not too much below the required level. Using the upper bound for the variance will give conservative confidence intervals but also larger standard errors. Averaging individual group survival curves should only be considered for situations with large groups.

Computer Simulation↗
PubMed1994

Cancer incidence: life table risk versus cumulative risk.

STUDY OBJECTIVE: To study differences between various methods of estimating cancer risk in individuals. DESIGN: Information was obtained from a cancer registry. Lifetime risk was calculated using the life table method, taking competing causes of death into account and using well recognised methods such as the cumulative rate and risk. SETTING: Regional cancer registry of the Comprehensive Cancer Centre IKL, located in Maastricht, The Netherlands. PATIENTS: Patients with a first primary malignancy in 1989-90 in the catchment area of the cancer registry. MAIN RESULTS: The lifetime risk of developing cancer was estimated to be 34.8% for males and 30.4% for females. In males, especially, the risk estimates were considerably higher when the cumulative risk was used. CONCLUSIONS: The life table method is convenient for estimating the probability that a person will develop cancer during a defined period or during his or her lifetime. The other estimates overestimate the risk of the disease under investigation, especially in the very elderly.

Adolescent↗
PubMed1985

Survival in trisomy 18. Life tables for use in genetic counselling and clinical paediatrics.

Clinical management of neonates with Trisomy 18 depends on a knowledge of life expectancy. True estimates of potential life span are required for genetic counselling purposes when parents interpret the genetic threat, not only in terms of the mathematical odds involved, but also in terms of the quality and length of life of an affected infant, should such be born. This paper reports the findings from a study to generate life tables for Trisomy 18. This study is a total population study over 10 years based on a primary population of 2.2 million. Forty-eight cases of Trisomy 18 were identified, five at amniocentesis. Four of the 43 clinical cases (9%) were mosaics. The median life expectancy for live-born infants was five days (range one hour to 18 months). Mean age at death was 48 days. Life tables, by sex and by sub-types (associated congenital abnormalities) are presented. The annual incidence is 14 per 100,000 total births, with a prevalence estimate of 0.06 per 100,000 total population.

Chromosomes, Human, 4-5↗
PubMed1987

Suicide in middle age and later life: sex and race specific life table and cohort analyses.

Cross-temporal data on suicide for the period 1962 to 1981 from the National Center for Health Statistics were analyzed. These data were used to estimate period and cohort suicide rates for the four middle-aged and elderly groups (ages 45 to 64, 65 to 74, 75 to 84, and 85 and older) by sex and race. Statistical procedures included multiple decrement life table analyses and cause elimination life table analyses for each year 1968 to 1981. Results from an age, period, cohort analysis of cohort trends 1962 to 1981 also were presented. The analysis showed that suicide continues to be a serious problem in later life especially among the "oldest-old" (those aged 85 and over) and among nonwhite males. It also showed important differences in cohort risks that may strongly affect future suicide risks among elderly adults.

Actuarial Analysis↗
PubMed2003

[Life-table of Helicoverpa armigera in northern China and characters of population development in southern and northern China].

The population dynamics of Helicoverpa armigera in Raoyang County, Hebei Province as an example in Northern China was researched, and its natural life-table was established. The results showed that total mortality of first to fourth generations of cotton bollworm in Northern China were 98.3%, 98.34%, 98.69% and 99.13%, and the population tendency index (I) were 3.97, 1.50, 1.41 and 1.09, respectively. A comparative analysis of the natural life-table of cotton bollworm in Southern China and in Northern China showed that the survival curves were concave curves in the two cotton zones. The curve showed that the mortality of cotton bollworm was higher in its egg stage to the second instar, and lower after the third instar. The key death factor of cotton bollworm was the scouring effect of rain and wind in Southern China, and the predation of its natural enemies in Northern China. The hatch period to the first instar was the key stage in Northern China and Southern China, and in this time, its larva instar was slim, fragile and sensitive to bad circumstances, so its mortality was higher. The second and third generations were the key damage generations in Northern China, while the third and fourth generations were the key damage generations in Southern China. The development and damage characters of each generation in Northern China and in Southern China were discussed.

Animals↗
PubMed1991

The fetal life table revisited: spontaneous abortion rates in three Kaiser Permanente cohorts.

A cohort of 9,055 singleton pregnancies was identified by conventional urine tests or physician examination at the Kaiser Permanente Medical Care Program in Northern California in 1981-1982. Using life table methods, we estimated the cumulative risk of spontaneous abortion or fetal death through the end of pregnancy as 13.0% of all pregnancies surviving 1 week or more past the time of the first missed menses. This value was lower than the estimates of 15.1% and 16.0%, respectively, from two previous fetal life table studies conducted at Kaiser Permanente in prior decades, but similar to estimates from recent, smaller studies of early pregnancy diagnosed by human chorionic gonadotropin. The major difference in survival between the three Kaiser Permanente cohorts was in the earliest gestational week of observation, week 5 from the last menstrual period, where the older data were sparse and potentially biased. High loss rates during this week accounted for one-fourth to one-third of the cumulative risk observed in the older studies. Although the older cohorts were larger, the 1981-1982 cohort included five times and three times as many pregnancies under observation during week 5 from the last menstrual period, yielding more stable estimates for this period. Because of improved reliability of early pregnancy testing and an emphasis on early prenatal care, the mean gestational age at entry to the 1981-1982 cohort was 10.4 weeks from the last menstrual period compared to 14.3 weeks and 13.7 weeks for the older studies. All three studies showed a peak for risk of spontaneous abortion around weeks 10-12 from the last menstrual period.

Abortion, Spontaneous↗
PubMed1983

Life-table factors for use in estimating the cancer risk of radiation exposure to workers.

Recent publications have discussed the use of life-tables in estimating the risks of radiation-induced cancer (Bu81; Ha81). These studies have been useful in estimating the hazards to groups of individuals exposed to radiation. However, they are not always presented in a way which is useful to health physicists. Life-table factors are presented here which may be of use in calculating such risks to individuals or groups.

Actuarial Analysis↗
PubMed1991

Life table analysis of fecundity in intravenously gonadotropin-releasing hormone-treated patients with normogonadotropic and hypogonadotropic amenorrhea.

The success of pulsatile intravenous (IV) gonadotropin-releasing hormone (GnRH) treatment in patients with normogonadotropic and hypogonadotropic amenorrhea was studied retrospectively using life table analysis. Two hundred forty-four ovulatory cycles in 48 normogonadotropic and hypogonadotropic patients were evaluated. The cumulative conception rate after 12 cycles was 93%, with a mean conception rate of 22.5% per cycle. Comparing cycles 1 to 6 with cycles 7 to 12, no significant difference in conception rate was observed. Subdivisions were made relative to the presence of additional infertility factors, history of weight loss, actual weight, estrogenic status, and primary versus secondary amenorrhea. The life table curves of patients either with or without other infertility factors were significantly different. No statistically significant differences were found in the other subdivisions. It is concluded that IV GnRH therapy is highly successful in patients with normogonadotropic and hypogonadotropic amenorrhea, especially if no other infertility factors are present.

Adult↗
PubMedDate not supplied

Marital status life table for Australian women, 1971.

"In this paper the mathematical principles behind the construction of multistate life tables are presented. [They are] then applied to study the patterns of first marriage, widowhood, divorce and remarriage of the Australian female population for the year 1971." Comparisons are also made with data for the United States in 1970. The author finds that "the first marriage patterns of both countries are very similar. But the divorce pattern is different. Though the probability that a marriage will end in a divorce is much lower in Australia than in the United States, the proportion of divorcees remarrying is only slightly lower in Australia.... Expected duration of a marriage is about 10.5 years longer in Australia than in the United States." (summary in FRE, ITA)

Australia↗
PubMed2004

Evidence from data searches and life-table analyses for gender-related differences in absolute risk of hip fracture after Colles' or spine fracture: Colles' fracture as an early and sensitive marker of skeletal fragility in white men.

UNLABELLED: Based on data searches and life-table analyses, we determined the long-term (remaining lifetime) and short-term (10- and 5-year) absolute risks of hip fracture after sustaining a Colles' or spine fracture and searched for potential gender-related differences. In aging men, Colles' fractures carry a higher absolute risk for hip fracture than spinal fractures in contrast to women. These findings support the concept that forearm fracture is an early and sensitive marker of male skeletal fragility. INTRODUCTION: Colles' fracture occurrence has been largely ignored in public health approaches to identify target populations at risk for hip fracture. The aim of this study was to estimate the long-term and short-term absolute risks of hip fracture after sustaining a Colles' or spine fracture and to search for potential gender-related differences in the relationship between fracture history and future fracture risk. MATERIALS AND METHODS: To determine the long-term (remaining lifetime) and short-term (10- and 5-year) absolute risks of hip fracture, we applied life-table methods using U.S. age- and sex-specific hip fracture incidence rates, U.S. age-specific mortality rates for white women and men, pooled hazard ratios for mortality after Colles' and spine fracture, and pooled relative risks for hip fracture after Colles' and spine fracture, estimated from cohort studies by standard meta-analytic methods. RESULTS: Our results indicate that the estimated remaining lifetime risks are dependent on age in both genders. In women, remaining lifetime risks increase until the age of 80 years, when they start to decline because of the competing probabilities of fracture and death. The same pattern is found in men until the age of 85 years, the increment in lifetime risk being even more pronounced. As expected, the risk of sustaining a hip fracture was found to be higher in postmenopausal women with a previous spine fracture compared with those with a history of Colles' fracture. In men, on the other hand, the prospective association between fracture history and subsequent hip fracture risk seemed to be strongest for Colles' fracture. At the age of 50, for example, the remaining lifetime risk was 13% in women with a previous Colles' fracture compared with 15% in the context of a previous spine fracture and 9% among women of the general population. In men at the age of 50 years, the corresponding risk estimates were 8%, 6%, and 3%, respectively. Similar trends were observed when calculating 5- and 10-year risks. CONCLUSIONS: In aging men, Colles' fractures carry a higher absolute risk for hip fracture than spinal fractures in contrast to women. These findings support the concept that forearm fracture is an early and sensitive marker of male skeletal fragility. The gender-related differences reported in this analysis should be taken into account when designing screening and treatment strategies for prevention of hip fracture in men.

Age Factors↗
PubMed1990

[A continuous-step density percoll gradient for use in AIH and life table analysis of pregnancy rates].

For use in artificial insemination with husband's semen (AIH), a continuous-step Percoll density gradient technique was used to wash and concentrate sperm from ejaculate. To evaluate usefulness, the pregnancy rates were analyzed by the life table method. 1. After washing by the continuous-step Percoll density gradient method, sperm density increased from 28.8 X 10(6)/ml (original semen) to 40.9 X 10(6)/ml and sperm motility improved from 52.4% (original semen) to 77.0% respectively. 2. A group of 119 infertile patients whose diagnosis involved oligoasthenozoospermia, cervical factor and unexplained infertility were selected for AIH. After 640 insemination cycles, 37 women conceived with a pregnancy rate of 31.1%. By using life table analysis, the cumulative conception probability rate reached 0.652 after 13 insemination cycles. 3. Cumulative pregnancy rates by diagnostic category were 0.494 in male factor and 0.745 in cervical factor after 12 cycles, respectively. 4. The poorest results were obtained in unexplained infertility with a cumulative pregnancy rate of only 0.355 after 12 cycles. 5. In the follow up study, 24 viable babies were born and seven (18.9%) resulted in spontaneous abortion in the first trimester. These results indicate that the continuous-step Percoll density gradient technique is useful for improving the pregnancy rate in AIH.

Adult↗
PubMed1997

Life-table attributes of Anopheles albimanus (Wiedemann) under controlled laboratory conditions.

The life-table attributes of a laboratory-colonized strain of Anopheles albimanus Wiedemann from El Salvador were investigated under controlled environmental conditions (26 +/- 2 degrees C, 60 +/- 2% RH, and 16:8 L:D photoperiod). Larvae pupated seven days after eclosion and the adults emerged on day eight. Adult emergence success was 91% and sex ratio was not significantly different from 1:1. Females took a blood meal one day after emergence and laid eggs two days later. The mean time of reproduction was 10.8 days and the expectation of life at emergence was 18.8 and 14.1 days for females and males, respectively. The daily survivorship of females at emergence was 0.97, and their net reproductive rate, age at mean cohort reproduction, instantaneous rate of increase, and mean generation time was 309.2, 10.8 days, 0.319, and 18 days, respectively. The life expectancy of females 10 days after emergence was 13.4 days, and they were capable of taking four to six additional blood meals.

Animals↗
PubMed1989

Active life among the elderly in the United States: multistate life-table estimates and population projections.

Calculations of multistate life expectancy not only measure how long a population may live beyond a certain age, but also what fractions of this continuing lifetime will be spent in an independent or dependent status. Many Americans aged 70 and over are leading long, active lives; large numbers of individuals who become dependent, moreover, do so temporarily and return to independent status. Men and women have disparate total and active life expectancies, however, reflecting differential survival patterns and varying rates of transition among statuses. Policy makers must consider the increased size of the future elderly population, and changes in its age composition and functional status, when planning relevant health services.

Activities of Daily Living↗
PubMed1996

Family and fertility careers of Polish females: a semi-parametric and life table approach.

"In this paper an evaluation has been made using the semi-parametric analysis and life table method of changes in the process of formation and dissolution of families in Poland, and changes in fertility careers by cohorts. An answer was sought to the following questions: What are the factors significantly determining the process studied? What differences appear between cohorts?"

Cohort Studies↗
PubMed1989

A probabilistic approach to the construction of competing-risk life tables.

"This paper aims to identify net and partial-crude probabilities in the competing-risk life table context, by using probabilistic approaches. Five types of lifelength random variables are defined to formulate these nonidentifiable probabilities. General expressions for net and partial-crude probabilities are first derived under independent risks assumptions. Two sets of explicit formulas for estimating the net and partial-crude probabilities are then derived in terms of the identifiable overall and crude probabilities by making the additional assumption of piecewise uniform distribution of the lifelength random variables. A study of the degree to which nonidentifiability can affect the net and partial-crude probabilities in a variety of situations is developed. An example from cross-sectional studies is employed to illustrate the methodology developed."

Biology↗
PubMed2003

[Establishment and analysis of laboratory population life table of Trichogramma dendrolimi developed on Antherea pernyi eggs].

The laboratory population life table of Trichogramma dendrolimi Matsumura developed on the eggs of Antherea pernyi was established by calculating the survival rate at immature stage and the adult reproduction. The survival rate of egg, larval and pupa was 1.00, 0.9186 and 0.8895, respectively, and the emergence rate of pupa was 0.8668. The total mortality rate at immature stage reached to 30%, which was a great difference from those developed on small host eggs. Each Trichogramma female could lay about 86 eggs on one Antherea pernyi egg. The index of Trichogramma population trend was 54.48. Analysis on the relationships among intrinsic rate of natural increase (rm), net production rate (R0) and index of population trend (I) showed that the R0 and I had the same biological meaning, and rm could be calculated with I value.

Animals↗
PubMed2006

Life tables and development of Bemisia argentifolii (Homoptera: Aleyrodidae) at different temperatures.

The life history of Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) on tomato (Lycopersicum spp.) was studied based on the age-stage, two-sex life table at 15, 20, 25, 28, 30, and 35 degrees C. The intrinsic rate of increase (r) at these temperatures is -0.0176, 0.0667, 0.1469, 0.1611, 0.1745, and 0.0989 d(-1), respectively. The relationship among the gross reproductive rate (GRR), the net reproductive rate (R0), and the preadult survivorship (l(a)) is consistent with GRR > l(a) x GRR > R0 for all results at different temperatures. The mean generation time is 81.9, 48.6, 28.4, 25.3, 22.1, and 18.2 d, respectively. The developmental rate of the egg stage at different temperatures fit a linear equation with a thermal summation 89.2 degree-days and a developmental threshold of 11.4 degrees C. The developmental rates of the nymphal stage fit the model of Stinner et al. and the parameters of C, Rmax, k1 and k2 were 0.085, 0.0833, 5.298, and -0.263, respectively.

Age Factors↗
PubMed2003

Obesity in adulthood and its consequences for life expectancy: a life-table analysis.

BACKGROUND: Overweight and obesity in adulthood are linked to an increased risk for death and disease. Their potential effect on life expectancy and premature death has not yet been described. OBJECTIVE: To analyze reductions in life expectancy and increases in premature death associated with overweight and obesity at 40 years of age. DESIGN: Prospective cohort study. SETTING: The Framingham Heart Study with follow-up from 1948 to 1990. PARTICIPANTS: 3457 Framingham Heart Study participants who were 30 to 49 years of age at baseline. MEASUREMENTS: Mortality rates specific for age and body mass index group (normal weight, overweight, or obese at baseline) were derived within sex and smoking status strata. Life expectancy and the probability of death before 70 years of age were analyzed by using life tables. RESULTS: Large decreases in life expectancy were associated with overweight and obesity. Forty-year-old female nonsmokers lost 3.3 years and 40-year-old male nonsmokers lost 3.1 years of life expectancy because of overweight. Forty-year-old female nonsmokers lost 7.1 years and 40-year-old male nonsmokers lost 5.8 years because of obesity. Obese female smokers lost 7.2 years and obese male smokers lost 6.7 years of life expectancy compared with normal-weight smokers. Obese female smokers lost 13.3 years and obese male smokers lost 13.7 years compared with normal-weight nonsmokers. Body mass index at ages 30 to 49 years predicted mortality after ages 50 to 69 years, even after adjustment for body mass index at age 50 to 69 years. CONCLUSIONS: Obesity and overweight in adulthood are associated with large decreases in life expectancy and increases in early mortality. These decreases are similar to those seen with smoking. Obesity in adulthood is a powerful predictor of death at older ages. Because of the increasing prevalence of obesity, more efficient prevention and treatment should become high priorities in public health.

Adult↗