Comment on ‘Generating survival times to simulate Cox proportional hazards models with time-varying covariates’

2013

Optimal selection of individuals for repeated covariate measurements in follow-up studies

2016

Repeated covariate measurements bring important information on the time-varying risk factors in long epidemiological follow-up studies. However, due to budget limitations, it may be possible to carry out the repeated measurements only for a subset of the cohort. We study cost-efficient alternatives for the simple random sampling in the selection of the individuals to be remeasured. The proposed selection criteria are based on forms of the D-optimality. The selection methods are compared with the simulation studies and illustrated with the data from the East–West study carried out in Finland from 1959 to 1999. The results indicate that cost savings can be achieved if the selection is focuse…

Lifetime cumulative risk factors predict cardiovascular disease mortality in a 50-year follow-up study in Finland.

2015

Summary. Background. Systolic blood pressure, total cholesterol and smoking are known predictors of cardiovascular disease (CVD) mortality. Less is known about the effect of lifetime accumulation and changes of risk factors over time as predictors of CVD mortality, especially in very long follow-up studies. Methods. Data from the Finnish cohorts of the Seven Countries Study were used. The baseline examination was in 1959 and seven re-examinations were carried out approximately in five-year intervals. Cohorts were followed up for mortality until the end of 2011. Time-dependent Cox models with regular time-updated risk factors, time-dependent averages of risk factors and latest changes in ris…

Living alone and positive mental health: a systematic review

2019

Background Living alone has become more common in today’s societies. Despite the high number of the population living alone, research directed towards the mental wellbeing issues related to living alone has been limited. This systematic literature review aimed to assess the association between living alone and positive mental health. Methods We conducted searches in Medline, Web of Science, Cochrane Library, CINAHL, PsycINFO, and other complementary databases from January 1998 to May 2019. Randomised trials and observational studies investigating adults over 18 years of age and living alone (defined as living in a single household or a household size of one person) were eligible. The primar…

Bayesian subcohort selection for longitudinal covariate measurements in follow‐up studies

2022

We propose an approach for the planning of longitudinal covariate measurements in follow-up studies where covariates are time-varying. We assume that the entire cohort cannot be selected for longitudinal measurements due to financial limitations, and study how a subset of the cohort should be selected optimally, in order to obtain precise estimates of covariate effects in a survival model. In our approach, the study will be designed sequentially utilizing the data collected in previous measurements of the individuals as prior information. We propose using a Bayesian optimality criterion in the subcohort selections, which is compared with simple random sampling using simulated and real follo…

How many longitudinal covariate measurements are needed for risk prediction?

2014

Abstract Objective In epidemiologic follow-up studies, many key covariates, such as smoking, use of medication, blood pressure, and cholesterol, are time varying. Because of practical and financial limitations, time-varying covariates cannot be measured continuously, but only at certain prespecified time points. We study how the number of these longitudinal measurements can be chosen cost-efficiently by evaluating the usefulness of the measurements for risk prediction. Study Design and Setting The usefulness is addressed by measuring the improvement in model discrimination between models using different amounts of longitudinal information. We use simulated follow-up data and the data from t…

Adjusting for selective non-participation with re-contact data in the FINRISK 2012 survey

2018

Aims: A common objective of epidemiological surveys is to provide population-level estimates of health indicators. Survey results tend to be biased under selective non-participation. One approach to bias reduction is to collect information about non-participants by contacting them again and asking them to fill in a questionnaire. This information is called re-contact data, and it allows to adjust the estimates for non-participation. Methods: We analyse data from the FINRISK 2012 survey, where re-contact data were collected. We assume that the respondents of the re-contact survey are similar to the remaining non-participants with respect to the health given their available background informa…

Participation rates by educational levels have diverged during 25 years in Finnish health examination surveys

2018

Background Declining participation rates in health examination surveys may impair the representativeness of surveys and introduce bias into the comparison of results between population groups if participation rates differ between them. Changes in the characteristics of non-participants over time may also limit comparability with earlier surveys. Methods We studied the association of socio-economic position with participation, and its changes over the past 25 years. Occupational class and educational level are used as indicators of socio-economic position. Data from six cross-sectional FINRISK surveys conducted between 1987 and 2012 in Finland were linked to national administrative registers…

Recommendations for design and analysis of health examination surveys under selective non-participation

2019

Background The decreasing participation rates and selective non-participation peril the representativeness of health examination surveys (HESs). Methods Finnish HESs conducted in 1972–2012 are used to demonstrate that survey participation rates can be enhanced with well-planned recruitment procedures and auxiliary information about survey non-participants can be used to reduce selection bias. Results Experiments incorporated to pilot surveys and experience from previously conducted surveys lead to practical improvements. For example, SMS reminders were taken as a routine procedure to the Finnish HESs after testing their effect on a pilot study and finding them as a cost-effective way to inc…

Non-participation modestly increased with distance to the examination clinic among adults in Finnish health examination surveys

2018

Aims: Health examination surveys (HES) provide important information about population health and health-related factors, but declining participation rates threaten the representativeness of collected data. It is hard to conduct national HESs at examination clinics near to every sampled individual. Thus, it is interesting to look into the possible association between the distance from home to the examination clinic and non-participation, and whether there is a certain distance after which the participation activity decreases considerably. Methods: Data from two national HESs conducted in Finland in 2011 and 2012 were used and a logistic regression model was fitted to investigate how distanc…

Bayesian subcohort selection for longitudinal covariate measurements in follow-up studies

2016

We consider planning longitudinal covariate measurements in follow-up studies where covariates are time-varying. We assume that the entire cohort cannot be selected for longitudinal measurements due to financial limitations and study how a subset of the cohort should be selected optimally in order to obtain precise estimates of covariate effects in a survival model. In our approach, the study will be designed sequentially utilizing the data collected in previous measurements of the individuals as prior information. We propose using a Bayesian optimality criterion in the subcohort selections, which is compared with simple random sampling using simulated and real follow-up data. This study ex…

Additional file 1: of Living alone and positive mental health: a systematic review

2019

PRISMA checklist. This file presents the PRISMA 2009 checklist employed in the study. (DOC 65 kb)

Menetelmiä regressiomallin estimointiin kompleksisessa otanta-asetelmassa : sovellus PISA 2009 -aineistoon

2012

Additional file 4: of Living alone and positive mental health: a systematic review

2019

JBI critical appraisal checklist for prevalence studies. This file presents the JBI critical appraisal checklist for studies reporting prevalence data. (DOCX 17 kb)

Additional file 3: of Living alone and positive mental health: a systematic review

2019

Search strategies by database. This file presents the search strategies by each database employed in the study. (DOCX 35 kb)

Additional file 1: of Living alone and positive mental health: a systematic review

2019

PRISMA checklist. This file presents the PRISMA 2009 checklist employed in the study. (DOC 65 kb)

Additional file 2: of Living alone and positive mental health: a systematic review

2019

Review protocol. This file presents the protocol of the study. (DOC 93 kb)

Additional file 3: of Living alone and positive mental health: a systematic review

2019

Search strategies by database. This file presents the search strategies by each database employed in the study. (DOCX 35 kb)

Additional file 4: of Living alone and positive mental health: a systematic review

2019

JBI critical appraisal checklist for prevalence studies. This file presents the JBI critical appraisal checklist for studies reporting prevalence data. (DOCX 17 kb)

Efficient design and modeling strategies for follow-up studies with time-varying covariates

2015

Epidemiological studies can often be designed in several ways, some of which may be more optimal than others. Possible designs may differ in the required resources or the ability to provide reliable answers to the questions under study. In addition, once the data are collected, the selected modeling approach may affect how efficiently the data are utilized. The purpose of this dissertation is to investigate efficient designs and analysis meth ods in follow-up studies with longitudinal measurements. A key question is how to select optimally a subcohort for a new longitudinal covariate measurement if we cannot afford to measure the entire cohort. Another key question we consider is how to determine …

Additional file 2: of Living alone and positive mental health: a systematic review

2019

Review protocol. This file presents the protocol of the study. (DOC 93 kb)