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Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke

BACKGROUND: We plan to conduct a case-control study to investigate whether exposure to nitrogen dioxide (NO(2)) increases the risk of stroke. In case-control studies, selective participation can lead to bias and loss of efficiency. A two-phase design can reduce bias and improve efficiency by combini...

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Autores principales: Oudin, Anna, Björk, Jonas, Strömberg, Ulf
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2007
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2174445/
https://www.ncbi.nlm.nih.gov/pubmed/17988388
http://dx.doi.org/10.1186/1476-069X-6-34
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author Oudin, Anna
Björk, Jonas
Strömberg, Ulf
author_facet Oudin, Anna
Björk, Jonas
Strömberg, Ulf
author_sort Oudin, Anna
collection PubMed
description BACKGROUND: We plan to conduct a case-control study to investigate whether exposure to nitrogen dioxide (NO(2)) increases the risk of stroke. In case-control studies, selective participation can lead to bias and loss of efficiency. A two-phase design can reduce bias and improve efficiency by combining information on the non-participating subjects with information from the participating subjects. In our planned study, we will have access to individual disease status and data on NO(2 )exposure on group (area) level for a large population sample of Scania, southern Sweden. A smaller sub-sample will be selected to the second phase for individual-level assessment on exposure and covariables. In this paper, we simulate a case-control study based on our planned study. We develop a two-phase method for this study and compare the performance of our method with the performance of other two-phase methods. METHODS: A two-phase case-control study was simulated with a varying number of first- and second-phase subjects. Estimation methods: Method 1: Effect estimation with second-phase data only. Method 2: Effect estimation by adjusting the first-phase estimate with the difference between the adjusted and unadjusted second-phase estimate. The first-phase estimate is based on individual disease status and residential address for all study subjects that are linked to register data on NO(2)-exposure for each geographical area. Method 3: Effect estimation by using the expectation-maximization (EM) algorithm without taking area-level register data on exposure into account. Method 4: Effect estimation by using the EM algorithm and incorporating group-level register data on NO(2)-exposure. RESULTS: The simulated scenarios were such that, unbiased or marginally biased (< 7%) odds ratio (OR) estimates were obtained with all methods. The efficiencies of method 4, are generally higher than those of methods 1 and 2. The standard errors in method 4 decreased further when the case/control ratio is above one in the second phase. For all methods, the standard errors do not become substantially reduced when the number of first-phase controls is increased. CONCLUSION: In the setting described here, method 4 had the best performance in order to improve efficiency, while adjusting for varying participation rates across areas.
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spelling pubmed-21744452008-01-04 Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke Oudin, Anna Björk, Jonas Strömberg, Ulf Environ Health Research BACKGROUND: We plan to conduct a case-control study to investigate whether exposure to nitrogen dioxide (NO(2)) increases the risk of stroke. In case-control studies, selective participation can lead to bias and loss of efficiency. A two-phase design can reduce bias and improve efficiency by combining information on the non-participating subjects with information from the participating subjects. In our planned study, we will have access to individual disease status and data on NO(2 )exposure on group (area) level for a large population sample of Scania, southern Sweden. A smaller sub-sample will be selected to the second phase for individual-level assessment on exposure and covariables. In this paper, we simulate a case-control study based on our planned study. We develop a two-phase method for this study and compare the performance of our method with the performance of other two-phase methods. METHODS: A two-phase case-control study was simulated with a varying number of first- and second-phase subjects. Estimation methods: Method 1: Effect estimation with second-phase data only. Method 2: Effect estimation by adjusting the first-phase estimate with the difference between the adjusted and unadjusted second-phase estimate. The first-phase estimate is based on individual disease status and residential address for all study subjects that are linked to register data on NO(2)-exposure for each geographical area. Method 3: Effect estimation by using the expectation-maximization (EM) algorithm without taking area-level register data on exposure into account. Method 4: Effect estimation by using the EM algorithm and incorporating group-level register data on NO(2)-exposure. RESULTS: The simulated scenarios were such that, unbiased or marginally biased (< 7%) odds ratio (OR) estimates were obtained with all methods. The efficiencies of method 4, are generally higher than those of methods 1 and 2. The standard errors in method 4 decreased further when the case/control ratio is above one in the second phase. For all methods, the standard errors do not become substantially reduced when the number of first-phase controls is increased. CONCLUSION: In the setting described here, method 4 had the best performance in order to improve efficiency, while adjusting for varying participation rates across areas. BioMed Central 2007-11-07 /pmc/articles/PMC2174445/ /pubmed/17988388 http://dx.doi.org/10.1186/1476-069X-6-34 Text en Copyright © 2007 Oudin et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research
Oudin, Anna
Björk, Jonas
Strömberg, Ulf
Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
title Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
title_full Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
title_fullStr Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
title_full_unstemmed Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
title_short Efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
title_sort efficiency of two-phase methods with focus on a planned population-based case-control study on air pollution and stroke
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2174445/
https://www.ncbi.nlm.nih.gov/pubmed/17988388
http://dx.doi.org/10.1186/1476-069X-6-34
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