blue_ocean

EBM

4 posts in this topic

The following is extracted from an article on the association between schizophrenia and obstetric complications. Dalman et al, The British Journal of Psychiatry (2001), 179:403-8. Methods: From the Stockholm County In-Patient Register and community registers, the authors identified 524 individuals born in Stockholm since January 1960 who had been in-patients and had received a diagnosis of schizophrenia between January 1971 and June 1994 (n=648; of which 120 were excluded - Deaths (n=51), not resident in Stockholm county (n=32), birth records could not be retrieved (n=37)). For each case, 2 controls of same gender, resident in the same county, and born next in time from the same hospital were identified. As four cases did not have well-matched controls, they were excluded. In total 524 patients with schizophrenia and 1043 controls were included. Data on obstetric complications were obtained from birth records. APGAR scores for asphyxia were assigned by a midwife using the birth records, and confirmed by 2 paediatricians independently with excellent agreement between the two raters (? 0.83). In addition, the presence or absence of pre-eclampsia was also recorded in accordance with a predefined criteria. Other indicators of foetal growth impairment such as low birth weight, delay (>7 days) in gaining weight after birth, birth length and head circumference were also recorded. Indicators of hypoxia/ischaemia around birth such as emergency Caesarean section, placental abruption, cord prolapse, foetal heart rate <100 or >160 b.p.m., and prolonged hospital stay for the child were also noted. Odds ratios (ORs) and 95% confidence intervals (CIs) for schizophrenia in relation to individual obstetric complications were calculated for matched case—control sets using conditional logistic regression. Odds ratios were adjusted for possible confounding variables, both one by one and simultaneously. Results: The results are shown in the table. Adjusting either separately or simultaneously for maternal history of psychotic illness, maternal age, parity, socio-economic classification, civil status and attendance at antenatal care did not substantially alter the odds ratios for most of the obstetric complications listed. However, after adjusting for these possible confounding variables, the odds ratio for schizophrenia in relation to signs of asphyxia at birth was increased to 4.5 (95% CI 2.2-9.5). The authors estimated a population-attributable fraction for birth asphyxia as 7.7% for schizophrenia using the data for population prevalence of birth asphyxia in Stockholm (not discussed in the study). Comparatively uncommon exposures such as pre-eclampsia, low birth-weight and short gestational age (<33 weeks) showed increased risk estimates but were not statistically significant. The strengths of associations between schizophrenia and all other complications were reduced and no longer statistically significant after the statistical adjustments. Which of the following exposures showed a statistically significant association with schizophrenia before adjusting for potential confounders, but lost its significance upon adjustment?

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What's the correct answer:

a. Lower birth weight
b. Pre-eclampsia
c. None of the studied factors
d. Greater delay in gaining weight
e. Child remaining in the hospital
 

Edited by blue_ocean

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C

 

None of the studied factors

Agree with you. Any explanation please 

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Agree with both of you.

The answer is C

An exposure must show significant effect before adjustment i.e Odds ratio(95% CI) must not touch value of no significance i.e 1

And

Must become non significant  on controlling for possible confounders (middle column of odds ratios)

None of the above factors satisfy this

Edited by psychtrainee2015
transcription error

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