J Prev Med Public Health.  2010 Mar;43(2):159-165. 10.3961/jpmph.2010.43.2.159.

Reliability of Covariates in Baseline Survey of a Cohort Study: Epidemiological Investigation on Cancer Risk Among Residents Who Reside Near the Nuclear Power Plants in Korea

• Bae S
• Park BY
• Li ZM
• Ahn YO

• KMID: 1070500
• DOI: http://doi.org/10.3961/jpmph.2010.43.2.159

Abstract

OBJECTIVES
We evaluated the reliability of the possible covariates of the baseline survey data collected for the Epidemiological Investigation on Cancer Risk Among Residents Who Reside Near the Nuclear Power Plants in Korea.
METHODS
Follow-up surveys were conducted for 477 participants of the cohort at less than 1 year after the initial survey. The mean interval between the initial and follow-up surveys was 282.5 days. Possible covariates were identified by analyzing the correlations with the exposure variable and associations with the outcome variables for all the variables. Logistic regression analysis with stepwise selection was further conducted among the possible covariates to select variables that have covariance with other variables. We considered that these variables can be representing other variables. Seven variables for the males and 3 variables for the females, which had covariance with other possible covariates, were selected as representative variables. The Kappa index of each variable was calculated.
RESULTS
For the males, the Kappa indexes were as follow; family history of cancer was 0.64, family history of liver diseases in parents and siblings was 0.56, family history of hypertension in parents and siblings was 0.51, family history of liver diseases was 0.50, family history of hypertension was 0.44, a history of chronic liver diseases was 0.53 and history of pulmonary tuberculosis was 0.36. For females, the Kappa indexes were as follow; family history of cancer was 0.58, family history of hypertension in parents and siblings was 0.56 and family history of hypertension was 0.47.
CONCLUSIONS
Most of the possible covariates showed good to moderate agreement.

Keyword

Baseline survey; Cohort study; Confounding factors; Covariates; Effect modifiers; Reliability

MeSH Terms

Aged
Cohort Studies
Confounding Factors (Epidemiology)
Environmental Exposure/adverse effects
Female
Health Behavior
Health Surveys
Humans
Logistic Models
Male
Middle Aged
Neoplasms/*epidemiology/etiology
*Nuclear Power Plants
Republic of Korea/epidemiology
Sex Factors