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- Obel, C., et al.
(författare)
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Is maternal smoking during pregnancy a risk factor for Hyperkinetic disorder? : Findings from a sibling design
- 2011
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 40:2, s. 338-345
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Tidskriftsartikel (refereegranskat)abstract
- Background Studies have consistently shown that pregnancy smoking is associated with twice the risk of hyperactivity/inattention problems in the offspring. An association of this magnitude may indicate behavioural difficulties as one of the most important health effects related to smoking during pregnancy. However, social and genetic confounders may fully or partially account for these findings. Methods A cohort including all singletons born in Finland from 1 January 1987 through 31 December 2001 was followed until 1 January 2006 based on linkage of national registers. Data were available for 97% (N = 868 449) of the population. We followed singleton children of smoking and non-smoking mothers until they had an International Classification of Diseases, 10th revision, diagnosis of hyperkinetic disorder (HKD) or to the end of the observation period. We used sibling-matched Cox regression analyses to control for social and genetic confounding. Results We found a much smaller association between exposure to maternal smoking during pregnancy and risk of HKD in children using the sibling-matched analysis [hazards ratio (HR) = 1.20, 95% confidence interval (CI) 0.97-1.49] than was observed in the entire cohort (HR 2.01, 95% CI 1.90-2.12). Conclusions Our findings suggest that the strong association found in previous studies may be due to time-stable familial factors, such as environmental and genetic factors. If smoking is a causal factor, the effect is small and less important than what the previous studies indicate.
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- Hohwu, L., et al.
(författare)
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Web-Based Versus Traditional Paper Questionnaires: A Mixed-Mode Survey With a Nordic Perspective
- 2013
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Ingår i: Journal of Medical Internet Research. - : JMIR Publications Inc.. - 1438-8871. ; 15:8
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Tidskriftsartikel (refereegranskat)abstract
- Background: Survey response rates have been declining over the past decade. The more widespread use of the Internet and Web-based technologies among potential health survey participants suggests that Web-based questionnaires may be an alternative to paper questionnaires in future epidemiological studies. Objective: To compare response rates in a population of parents by using 4 different modes of data collection for a questionnaire survey of which 1 involved a nonmonetary incentive. Methods: A random sample of 3148 parents of Danish children aged 2-17 years were invited to participate in the Danish part of the NordChild 2011 survey on their children's health and welfare. NordChild was conducted in 1984 and 1996 in collaboration with Finland, Iceland, Norway, and Sweden using mailed paper questionnaires only. In 2011, all countries used conventional paper versions only except Denmark where the parents were randomized into 4 groups: (1) 789 received a paper questionnaire only (paper), (2) 786 received the paper questionnaire and a log-in code to the Web-based questionnaire (paper/Web), (3) 787 received a log-in code to the Web-based questionnaire (Web), and (4) 786 received log-in details to the Web-based questionnaire and were given an incentive consisting of a chance to win a tablet computer (Web/tablet). In connection with the first reminder, the nonresponders in the paper, paper/Web, and Web groups were also present with the opportunity to win a tablet computer as a means of motivation. Descriptive analysis was performed using chi-square tests. Odds ratios were used to estimate differences in response rates between the 4 modes. Results: In 2011, 1704 of 3148 (54.13%) respondents answered the Danish questionnaire. The highest response rate was with the paper mode (n=443, 56.2%). The other groups had similar response rates: paper/Web (n=422, 53.7%), Web (n=420, 53.4%), and Web/tablet (n=419, 53.3%) modes. Compared to the paper mode, the odds for response rate in the paper/Web decreased by 9% (OR 0.91, 95% CI 0.74-1.10) and by 11% (OR 0.89, 95% CI 0.73-1.09) in the Web and Web/tablet modes. The total number of responders for NordChild declined from 10,291 of 15,339 (67.09%) in 1984 and 10,667 of 15,254 (69.93%) in 1996 to 7805 of 15,945 (48.95%) in 2011 with similar declines in all 5 Nordic countries. Conclusions: Web-based questionnaires could replace traditional paper questionnaires with minor effects on response rates and lower costs. The increasing effect on the response rate on participants replying for a nonmonetary incentive could only be estimated within the 2 Web-based questionnaire modes before the first reminder. Alternative platforms to reach higher participation rates in population surveys should reflect the development of electronic devices and the ways in which the population primarily accesses the Internet.
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