survivor function
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2021 ◽  
Vol 11 (1) ◽  
pp. 54
Author(s):  
Ajay Pandey ◽  
Richa Sharma

Culturally, there is always pressure among newly-wed to conceive early and have births in India. Previous studies have documented relationship between age at first birth & fertility, besides the socio-demographic factors that influence age at first birth. The current study aims answering directions and quantum of such relationships using frailty models. The successive rounds of NFHS data (1, 2, 3 & 4) from Uttar Pradesh is used in the study. Fertility in India is characterized as too-early-too-fast. By age-30 majority women would have completed the childbearing. However, the data from NFHS-4 shows some striking changes in the initiation of child bearing in Uttar Pradesh breaking away from the stereotypes of too early too fast characterization. While 44.67 percent of the women aged 30-34 had experienced first birth by age 18 in the year 1992-93 (NFHS-1), the percentages declined during 2015-16 (NFHS-4) to 28.25%. However, by ages 26 majority of women (>95%) aged 30-34 have had experienced first birth. Births at younger age are also a reflection on enforcement of child-marriage restraint act & adherence to legal minimum age at marriage which is 18 for girls & 21 for boys. The data from NFHS-4 have some quality issues. Women aged as low as 5 have shown to have experienced first birth by that age. This may not be possible. The Kaplan Meier survival Graph provided the survival probabilities with respect of each predictor sub groups. The log rank test was used to test the equality of survivor function for each sub group of the predictor variable. The survivor function was significantly different among sub groups of the predictor variables except for the categories of ever use of contraception at NFHS1 and categories of religion across rounds of NFHS data. The Cox Proportional Hazards model was used to study the risk of first birth by socio demographic characteristics. The Frailty model capturing the unobserved heterogeneity in the event time was preferred over standard survival model. For the current study, gamma frailty with Weibull-hazard is used as it fits the data well. Age at marriage and women’s literacy significantly determines the Age at First Birth. The inverse relationship with regard to ever use of contraception needs further analysis. The model also predicts significant frailty with variance parameter (theta) greater than one across the NFHS datasets.


2021 ◽  
Vol 11 (3) ◽  
pp. 430-436
Author(s):  
Mohammed Elamin Hassan ◽  
Fakhereldeen Elhaj Esmial Musa

The paper aimed to investigate the performance of some parametric survivor function estimators based on Bayesian methodology with respect to bias and efficiency. A simulation was conducted based on Mote Carlo experiments with different sample sizes different (10, 30, 50, 75, 100). The bias and variance of mean square Error V(MSE) were selected as the basis of comparison. The methods of estimation used in this study are Maximum Likelihood, Bayesian with exponential as prior distribution and Bayesian with gamma as prior distribution. A Monte Carlo Simulation study showed that the Bayesian method with gamma as prior distribution was the best performance than the other methods. The study recommended that.


Open Heart ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. e001737
Author(s):  
Jenny Lund ◽  
Catherine L Saunders ◽  
Duncan Edwards ◽  
Jonathan Mant

ObjectiveTo describe patterns of anticoagulation prescription and persistence for those aged ≥65 years with atrial fibrillation (AF).MethodsDescriptive cohort study using electronic general practice records of patients in England, who attended an influenza vaccination aged ≥65 years and were diagnosed with AF between 2008 and 2018. Patients were stratified by 10-year age group and year of diagnosis. Proportion anticoagulated, type of anticoagulation (direct oral anticoagulant (DOAC) or warfarin) initiated at diagnosis and persistence with anticoagulation over time are reported.Results42 290 patients (49% female), aged 65–74 (n=11 722), 75–84 (n=19 055) and 85+ (n=11 513) years at AF diagnosis are included. Prescription of anticoagulation at diagnosis increased over the time period from 55% to 86% in people aged 65–74 years, from 54% to 86% in people aged 75–84 years and from 27% to 75% in people aged 85 years and over. By 2018, 92% of patients with newly diagnosed AF were started on a DOAC. Survivor function for 5-year persistence in patients prescribed DOAC was 0.80 (95% CI 0.77 to 0.82) and for warfarin 0.71 (95% CI 0.70 to 0.72). Survivor function for any anticoagulation at 5 years was 0.79 (95% CI 0.78 to 0.81), 0.73 (95% CI 0.72 to 0.75) and 0.58 (95% CI 0.59 to 0.64) for people aged 65–74, 75–84 and 85+ years, respectively.ConclusionsRates of anticoagulation in AF in those aged ≥65 years have increased from 2008 to 2018, over which time period there has been a shift from initiating anticoagulation with warfarin to DOAC. Persistence with anticoagulation is higher in people on DOACs than on warfarin and in people aged <85 years.


2021 ◽  
Author(s):  
J Lund ◽  
CL Saunders ◽  
D Edwards ◽  
J Mant

AbstractObjectiveTo describe patterns of anticogulation prescribing and persistence for those aged ≥65 years with atrial fibrillation (AF).MethodsDescriptive cohort study using electronic general practice records of patients in England who attended a flu vaccination aged ≥65, and were diagnosed with AF between 2008-2018. Patients were stratified by 10 year age group and year of diagnosis. Proportion anticoagulated, type of anticoagulation (direct oral anticoagulant (DOAC) or Warfarin) initiated at diagnosis, and persistence with anticoagulation over time are reported.Results42,290 patients (49% female), aged 65-74 (n=11,722), 75-84 (n=19,055) and 85+ (n=11,513) at AF diagnosis are included. Prescription of anticoagulation at diagnosis increased over the time period from 55% to 86% in people aged 65-74, from 54% to 86% in people aged 75-84 and from 27% to 75% in people aged 85 and over. No patients were prescribed DOACs as a first anticoagulation agent in 2008, by 201892% of new AF patients were started on DOACs. Survivor function for 5 year persistence for patients taking only a single type of anticoagulant was 0.80 (0.77:0.82) for DOACs and0.71(0.70:0.72) for warfarin, Survivor function for any anticoagulation at 5 years was0.79(0.78:0.81), 0.73(0.72:0.75), 0.58(0.59:0.64) for people aged 65-74, 75-84 and 85+ respectively.ConclusionsRates of anticoagulation for new AF in those aged ≥65 have increased from 2008 to 2018, over which time there has been a shift from initiating anticoaguation with warfarin to DOACs. Persistence with anticoagulation is higher in people on DOACs than on warfarin, and in people under the aged of 85.Key MessagesWhat is already known?Anticoagulation is a highly effective way of reducing the risk of stroke associated with AF, but is underused, particularly in older people. The introduction of DOACs has been associated with increasing use of anticoagulation in AF.What does this study add?Our study provides up to date information on anticoagulation for AF in older people who are most at risk of AF related stroke and highlights particular increases in use of anticoagulation in people aged 85 and over.DOACs are now the major class of anticoagulant prescribed to patients with new AF in UK general practice.Long term persistence with anticoagulation is higher with DOACs than warfarin, but drops in all age groups over 5 years.How might this impact on clinical practice?Improved uptake of anticoagulation at all ages removes one of the potential barriers to screening for atrial fibrillation, but new strategies may be needed to enhance longer term persistence with treatment.


2018 ◽  
Vol 28 (10-11) ◽  
pp. 3333-3345 ◽  
Author(s):  
David B Wolfson ◽  
Ana F Best ◽  
Vittorio Addona ◽  
Julian Wolfson ◽  
Shahinaz M Gadalla

It is frequently of interest to estimate the time that individuals survive with a disease, that is, to estimate the time between disease onset and occurrence of a clinical endpoint such as death. Epidemiologic survival data are commonly collected from either an incident cohort, whose members' disease onset occurs after the study baseline date, or from a cohort with prevalent disease that is followed forward in time. Incident cohort survival data are limited by study termination, while prevalent cohort data provide biased (left-truncated) survival data. In this article, we investigate the advantages of a study design featuring simultaneous follow-up of prevalent and incident cohorts to the estimation of the survivor function. Our analyses are supported by simulations and illustrated using data on survival after myotonic dystrophy diagnosis from the United Kingdom Clinical Practice Research Datalink (CPRD). We demonstrate that the NPMLE using combined incident and prevalent cohort data estimates the true survivor function very well, even for moderate sample sizes, and ameliorates the disadvantages of using a purely incident or prevalent cohort.


2018 ◽  
Vol 25 (8) ◽  
pp. 569-575 ◽  
Author(s):  
Michael J. McCarthy ◽  
Tamilyn Bakas ◽  
Jeffrey Schellinger ◽  
Katie Stapleton ◽  
Brett M. Kissela

Stroke ◽  
2018 ◽  
Vol 49 (Suppl_1) ◽  
Author(s):  
Michael J McCarthy ◽  
Tamilyn Bakas ◽  
Erik Nelson ◽  
Jeffrey Schellinger ◽  
Kalyn Black ◽  
...  

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