An improved model for the French genetic evaluation of dairy bulls on length of productive life of their daughters

2005 ◽  
Vol 80 (3) ◽  
pp. 249-256 ◽  
Author(s):  
V. Ducrocq
Keyword(s):  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Analysis Model ◽  
Genetic Trend ◽  
Hazard Functions ◽  
Stage Of Lactation ◽  
Dairy Bulls ◽  
Estimated Breeding Values ◽  
Improved Model ◽  
Efficiency Of Selection

AbstractFunctional longevity of dairy cows has been routinely evaluated in France since 1997 using a survival analysis model. Recently, we proposed a genetic trend validation test that could be used before including national data in an international evaluation of bulls on longevity of their daughters. Its application to the French Holstein data revealed a large overestimation of the genetic trend. It was found that the bias is the result of a change in the baseline hazard rate over time. A new proportional hazards model is proposed which accounts for this change. In the new model, the baseline is described as a stratified, piecewise Weibull hazard function within lactation, i.e. a function of the number of days since the most recent calving. Stratification is within year and parity. Different Weibull hazard functions are used over four periods: 0 to 270 days, 271 to 380 days, 381 days to day when dried, dry period until the next calving. The non-genetic effects included in the model were slightly different from the previous one. In particular the interaction effects between the within herd-year class of production and lactation number × stage of lactation on the one hand and year-season were accounted for. The estimated genetic variance was smaller than with the old model. The new genetic trend is almost flat. An illustration of the efficiency of selection on the estimated breeding values for longevity is presented.

A comparison of a linear and proportional hazards approach to analyse discrete longevity data in dairy cows

2000 ◽  
Vol 70 (2) ◽  
pp. 197-206 ◽  
Author(s):  
R. Lubbers ◽  
S. Brotherstone ◽  
V.P. Ducrocq ◽  
P.M. Visscher
Keyword(s):  
Discrete Time ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Weibull Model ◽  
Logarithmic Scale ◽  
Data Set ◽  
Breeding Values ◽  
Hazards Model ◽  
Estimated Breeding Values ◽  
The Uk

AbstractThe objective of this study was to compare two methods for analysis of longevity in dairy cattle. The first method, currently used for routine genetic evaluation in the UK, uses a linear model to analyse lifespan, i.e. the number of lactations a cow has survived or is expected to survive. The second method was based on the concept of proportional hazard, i.e. modelling the conditional survival probability of a cow as a function of time. Comparisons were based on estimated heritabilities, ranking of estimated breeding values of sires, estimated effects of covariates used in the final models, and the distribution of residuals. The same data set, 21497 observations on the number of lactations cows had survived, was used for both analyses, even in the presence of censored observations. Cows in the data were progeny of 487 sires. Heritability estimates for lifespan or survival were approximately 0·06 for both methods, using the definition of heritability on a logarithmic scale for the proportional hazards model. Correlations between breeding values for sires were high, with absolute values ranging from 0·93 to 0·98, depending on the model fitted. It was concluded that it may be justified to use the standard Weibull model even for discrete time measures such as the number of completed lactations, but that more research is needed in the area of discrete time variates.

scholarly journals Lifetime cumulative incidence of dementia in a community-dwelling elderly population in Japan

Neurology ◽  
2020 ◽  
Vol 95 (5) ◽  
pp. e508-e518
Author(s):  
Daigo Yoshida ◽  
Tomoyuki Ohara ◽  
Jun Hata ◽  
Mao Shibata ◽  
Yoichiro Hirakawa ◽  
...  
Keyword(s):  
Cumulative Incidence ◽  
Elderly Population ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Survival Function ◽  
Community Dwelling ◽  
Lifetime Risk ◽  
Hazard Functions ◽  
Japanese Elderly ◽  
Incidence Of Dementia

ObjectiveTo estimate the lifetime cumulative incidence of dementia and its subtypes from a community-dwelling elderly population in Japan.MethodsA total of 1,193 community-dwelling Japanese individuals without dementia, aged 60 years or older, were followed up prospectively for 17 years. The cumulative incidence of dementia was estimated based on a death- and dementia-free survival function and the hazard functions of dementia at each year, which were computed by using a Weibull proportional hazards model. The lifetime risk of dementia was defined as the cumulative incidence of dementia at the point in time when the survival probability of the population was estimated to be less than 0.5%.ResultsDuring the follow-up, 350 participants experienced some type of dementia; among them, 191 participants developed Alzheimer disease (AD) and 117 developed vascular dementia (VaD). The lifetime risk of dementia was 55% (95% confidence interval, 49%–60%). Women had an approximately 1.5 times greater lifetime risk of dementia than men (65% [57%–72%] vs 41% [33%–49%]). The lifetime risks of developing AD and VaD were 42% (35%–50%) and 16% (12%–21%) in women vs 20% (7%–34%) and 18% (13%–23%) in men, respectively.ConclusionLifetime risk of all dementia for Japanese elderly was substantial at approximately 50% or higher. This study suggests that the lifetime burden attributable to dementia in contemporary Japanese communities is immense.

Bayesian proportional hazards model with latent variables

2017 ◽  
Vol 28 (4) ◽  
pp. 986-1002 ◽  
Author(s):  
Deng Pan ◽  
Kai Kang ◽  
Chunjie Wang ◽  
Xinyuan Song
Keyword(s):  
Risk Factors ◽  
Factor Analysis ◽  
Exploratory Factor Analysis ◽  
Latent Variables ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Failure Time ◽  
Analysis Model ◽  
Factor Analysis Model ◽  
Hazards Model

We consider a joint modeling approach that incorporates latent variables into a proportional hazards model to examine the observed and latent risk factors of the failure time of interest. An exploratory factor analysis model is used to characterize the latent risk factors through multiple observed variables. In commonly used confirmatory factor analysis, the number of latent variables and their observed indicators are specified prior to analysis. By contrast, the exploratory factor analysis model allows such information to be fully determined by the data. A Bayesian approach coupled with efficient sampling methods is developed to conduct statistical inference, and the performance of the proposed methodology is confirmed through simulations. The model is applied to a study on the risk factors of chronic kidney disease for patients with type 2 diabetes.

scholarly journals Effect of Acetyl-L-Carnitine on Leukemia L1210 Resistant to Mitoxantrone

2000 ◽  
Vol 43 (4) ◽  
pp. 125-128
Author(s):  
Mohamed Niang ◽  
Milan Mělka
Keyword(s):  
Survival Time ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Present Report ◽  
Combined Therapy ◽  
Alkylating Agents ◽  
Optimal Dose ◽  
Metabolic Effects ◽  
Hazard Functions ◽  
Pharmacological Interactions

Supportive care in tumour chemotherapy is a subject of intensive research. The complications of cytostatic therapy are a cause of extensive research of their pharmacological interactions and side effects. The immunologic and biochemical changes accompanying tumours are the factor that is most responsible for the worsening of the physiology of the host. Regimens containing carnitine and it’s acetyl-derivative are used in many cases, among others even for preventing hepatotoxicity. Our hypothesis was to verify the supporting metabolic effects of acetyl-L-carnitine hydrochloride (ALC) in combined therapy with mitoxantrone (MX) and hepatotoxic cytostatic drugs including alkylating agents. This present report describes the effect of ALC in combination with MX on DBA/2 male mice bearing a transplantable L1210 leukemia resistant to MX. The criterion for evaluation of effect was the length of survival time of experimental animals. The proportional- hazards model quadratic in the drug dose (7) was used for survival time evaluation and optimal dose calculation. The hazard functions and the index of relative hazard were determined using Weibull distribution after logarithmic transformation of the entered data in each particular group. The dose-response curve was represented by a second-degree polynomial without absolute term. The combination therapy revealed that the optimal dose of ALC was 186 mg/kg s.c. This relation is shown in Fig.1. A significant effect of ALC (s.c.) in combined therapy with MX (6 mg/kg i.v.) given to animals bearing an experimental form of leukemia L1210/MX resistant to MX was proven at a level of probability p≤ 0.001. The effect of ALC in monotherapy was not demonstrable.

scholarly journals Genetic evaluation for functional longevity in Polish Simmental cattle

2017 ◽  
Vol 62 (No. 7) ◽  
pp. 276-286 ◽  
Author(s):  
M. Morek-Kopeć ◽  
A. Zarnecki
Keyword(s):  
Fixed Effects ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Average Length ◽  
Selection Index ◽  
Herd Size ◽  
Genetic Evaluation ◽  
Productive Life ◽  
Stage Of Lactation ◽  
Fat Yield

The Weibull proportional hazards model was applied for genetic evaluation of functional longevity in Polish Simmentals. Data consisted of production and disposal records for 12 527 Simmental cows, daughters of 294 sires, calving for the first time from 1995 to 2014 in 286 herds. Length of productive life of cows was calculated as number of days from the first calving to culling or censoring. Average length of productive life of 4462 cows with complete (uncensored) survival records was 1198 days (39.3 months); mean censoring time for the remaining 8065 cows was 1093 days (35.8 months). Functional longevity was defined as length of productive life corrected for production. The model included time-independent fixed effect of age at first calving, time-dependent fixed effects of year-season, parity-stage of lactation, annual change in herd size, relative fat yield and protein yield, and random herd-year-season and sire effects. Likelihood ratio tests showed a highly significant impact of all fixed effects on longevity, except for relative fat yield. Estimated sire variance was 0.069, resulting in the equivalent (accounting for censoring level) heritability of 0.09. Standardized relative breeding values (RBV) ranged from 71 to 139 (mean 101.4, SD 9.12). Average reliability of RBVs was 0.47. Moderate heritability supports the possibility of effective selection for functional longevity, which will be included in the total selection index for Polish Simmentals.

Age at Exposure to Parental Suicide and the Subsequent Risk of Suicide in Young People

Crisis ◽  
2018 ◽  
Vol 39 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Kuan-Ying Lee ◽  
Chung-Yi Li ◽  
Kun-Chia Chang ◽  
Tsung-Hsueh Lu ◽  
Ying-Yeh Chen
Keyword(s):  
Young People ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Cox Proportional Hazards ◽  
Cox Proportional Hazards Model ◽  
Birth Registry ◽  
Data Set ◽  
Parental Suicide ◽  
The Impact ◽  
Age At Exposure

Abstract. Background: We investigated the age at exposure to parental suicide and the risk of subsequent suicide completion in young people. The impact of parental and offspring sex was also examined. Method: Using a cohort study design, we linked Taiwan's Birth Registry (1978–1997) with Taiwan's Death Registry (1985–2009) and identified 40,249 children who had experienced maternal suicide (n = 14,431), paternal suicide (n = 26,887), or the suicide of both parents (n = 281). Each exposed child was matched to 10 children of the same sex and birth year whose parents were still alive. This yielded a total of 398,081 children for our non-exposed cohort. A Cox proportional hazards model was used to compare the suicide risk of the exposed and non-exposed groups. Results: Compared with the non-exposed group, offspring who were exposed to parental suicide were 3.91 times (95% confidence interval [CI] = 3.10–4.92 more likely to die by suicide after adjusting for baseline characteristics. The risk of suicide seemed to be lower in older male offspring (HR = 3.94, 95% CI = 2.57–6.06), but higher in older female offspring (HR = 5.30, 95% CI = 3.05–9.22). Stratified analyses based on parental sex revealed similar patterns as the combined analysis. Limitations: As only register-­based data were used, we were not able to explore the impact of variables not contained in the data set, such as the role of mental illness. Conclusion: Our findings suggest a prominent elevation in the risk of suicide among offspring who lost their parents to suicide. The risk elevation differed according to the sex of the afflicted offspring as well as to their age at exposure.

HRA Model for Hypercholesterolemia Based on a Longitudinal Health Database

1998 ◽  
Vol 37 (02) ◽  
pp. 130-133
Author(s):  
T. Kishimoto ◽  
Y. Iida ◽  
K. Yoshida ◽  
M. Miyakawa ◽  
H. Sugimori ◽  
...  
Keyword(s):  
Total Cholesterol ◽  
Proportional Hazards ◽  
Proportional Hazards Model ◽  
Model Analysis ◽  
Serum Total Cholesterol ◽  
Hazards Model ◽  
The Mean ◽  
Health Database ◽  
Observation Period

AbstractTo evaluate the risk factors for hypercholesterolemia, we examined 4,371 subjects (3,207 males and 1,164 females) who received medical checkups more than twice at an AMHTS in Tokyo during the period from 1976 through 1991; and whose serum total cholesterol was under 250 mg/dl. The mean follow-up duration was 6.6 years. A self-registering questionnaire was administered at the time of the health checkup. The endpoint of this study was the onset of hypercholesterolemia when the level of serum total cholesterol was 250 mg/dl and over. We compared two prognosis groups (normal and hypercholesterol) in terms of age, examination findings and lifestyle. After assessing each variable, we employed Cox's proportional hazards model analysis to determine the factors related to the occurrence of hypercholesterolemia. According to proportional hazards model analysis, total cholesterol, triglyceride and smoking at the beginning, and hypertension during the observation period were selected in males; and total cholesterol at the beginning and age were selected in females to determine the factors related to the occurrence of hypercholesterolemia.

Correlates of Child Mortality in Pakistan: A Hazards Model Analysis

1999 ◽  
Vol 38 (1) ◽  
pp. 85-118 ◽  
Author(s):  
Jennifer Benneti
Keyword(s):  
Child Mortality ◽  
Proportional Hazards ◽  
Contraceptive Use ◽  
Proportional Hazards Model ◽  
Economic Status ◽  
Model Analysis ◽  
Health Seeking ◽  
Large Cities ◽  
Number Of Children ◽  
Hazards Model

This study investigated factors associated with child mortality in an area in Rawalpindi, one of the large cities of Pakistan. Using both demographic and anthropological methods, the research was conducted to specifically examine the processes and mechanisms whereby a link is established between child mortality and its covariates. Controlling for the socio-economic status as a determinant of child mortality, the study population was limited to a lower income stratum living in a homogeneous environment where all households had equal access to health-related and other facilities. Results of the proportional hazards model analysis on 130I index children suggest that non-economic factors like maternal health-seeking behaviour were related to high child mortality. The cultural norm of bearing a large number of children was the most significant correlate. In order of significance, this was followed by contraceptive use, current age of the mother, age at marriage and the hygienic conditions of the household. The study provides strong evidence of familial clustering of mortality by order of the household.

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