OBJECTIVES: This study explored the extent of errors in gestational age as ascertained by last menstrual period. METHODS: More than 1.5 million birth records (covering the years 1967-1994) from the population-based Medical Birth Registry of Norway were used to study variation in gestational age within strata of birthweight. RESULTS: Within 100-g strata of birthweight, it was found that the observed gestational age distribution could be divided into 3 distinct underlying distributions separated by approximately 4 weeks. This pattern was present through all birthweight strata, from 200 g up to 4700 g. In addition, the apparent misclassification causing a gestational age 4 weeks too short was much more common among low-birthweight births than among heavier births. CONCLUSIONS: The separation of the gestational age distributions by intervals of close to 4 weeks suggests that errors in gestational age measurements are caused by factors related to menstrual bleeding. Furthermore, there is evidence for a strong relation between bleeding at the time of the next menstrual period after conception and low birthweight. This conclusion should be approached with caution because of the retrospective nature of the data.
OBJECTIVES: The purpose of this study was to assess the role of siblings in day care as a determinant of infants' risk of lower respiratory tract infections. METHODS: A total of 3238 children (86%) out of 3754 Oslo, Norway, newborns recruited in 1992/93 were followed for 1 year. RESULTS: In logistic regression analysis, the risk of infection was increased in (1) infants with one or more siblings compared with infants without siblings (adjusted odds ratio [OR] = 2.3; 95% confidence interval [CI] = 1.84, 2.85) and (2) infants with one or more siblings in day care compared with infants with siblings not in day care (adjusted OR = 1.7; 95% CI = 1.21, 2.26). CONCLUSIONS: The results suggest that siblings in day care outside the home increase infants' risk of lower respiratory tract infections.
OBJECTIVES: This study examined effects of racial/ethnic misclassification of American Indians and Alaskan Natives on Washington State death certificates. METHODS: Probabilistic record linkage were used to match the 1989-1997 state death files to the Northwest Tribal Registry. RESULTS: We identified matches for 2819 decedents, including 414 (14.7%) who had been misclassified as non-American Indians and Alaskan Natives on the death certificates. The likelihood of being correctly classified increased 3-fold for each higher level of American Indian and Alaskan Native ancestry (odds ratio = 2.88; 95% confidence interval [CI] = 2.51, 3.30) and decreased by 6.9% per calendar year (95% CI = 2.0, 11.5). CONCLUSIONS: Systematic biases on death certificates in Washington State persist. Methods to reduce misclassification can improve data quality and enhance efforts to measure and reduce racial/ethnic health disparities.
Comment In: American Journal of Public Health. 2002 Sep;92(9):138612197956
OBJECTIVES. The Groningen Activity Restriction Scale (GARS) is a non-disease-specific instrument to measure disability in activities of daily living (ADL) and instrumental activities of daily living (IADL). It was developed in studies of Dutch samples consisting of elderly or chronically ill people. The psychometric properties of the GARS demonstrated in these studies were highly satisfactory. This paper addresses the psychometric properties of the GARS across countries. METHODS. Data of 623 patients with recently diagnosed rheumatoid arthritis from four European countries were analyzed by means of a principal components analysis and a Mokken scale analysis for polychotomous items. RESULTS. The results of the analyses were highly satisfactory: there was one strong and reliable general factor representing one underlying dimension of disability in ADL and IADL, and there was a clear hierarchical ordering of the items included in the GARS. The validity of the GARS was strongly suggested by the pattern of associations of the GARS with age, sex, and other existing health status measures. CONCLUSIONS. The psychometric characteristics of the GARS, which measures disability in ADL and IADL simultaneously, make this instrument very useful for comparative research across countries.