Results
Among the 117 patients, 30 were children under 15 who were not contacted. 87 patients were contacted by phone between February 25th and 27th 2009. 7 did not meet the inclusion criteria. The 80 remaining persons were contacted and invited to participate. 42 persons did not want to enter the study and explained they had resumed their life with no sequelae. 38 persons were included (mean age 38.9 ± 16.6; 34.2% male; 11.7 ± 2.9 years of education). 38 paired controls were also recruited (mean age 38.7 ± 16.5; 34.2 % male; 11.4 ± 3.9 years of education). No difference was found between patients and controls for age, gender and education level (Figure 1, data reported for education). Patients were assessed for the study 50.9 ± 17.3 days after CO poisoning. They all fulfilled the CO poisoning diagnosis criteria. The COHb level was recorded for 24 out of the 38 patients (10.9% (±7.9)). No CT scan lesion was observed. 2 patients (5%) had received hyperbaric oxygen therapy, 6 (16%) had had normobaric oxygen therapy and 29 (76%) had received both. For 1 patient, the treatment received was not known. Causes of CO intoxication, initial symptoms and symptoms reported during the semi-structured interview are reported in Table 1.
Figure 1.
Group comparisons for education level and the five cognitive tests that showed significant differences. For the main measure of each test, we provide a graphical representation of the dispersion of the performance of each group using box-plots. Boxes represent the 25th and 75th percentiles, and the lines in the boxes indicate the medians. Notches display the variability of the median between samples. Upper and lower lines of whiskers represent minimum and maximum performance. Circles are outliers in each group, i.e. subjects whose performance fell outside minimum or maximum values of +/- 1.5 the difference between the 25th and 75th percentiles. D represents Cohen's D value. *indicates a significant difference (*: p < 0.05 and **: p < 0.01).
No difference was found between groups on the cognitive complaint questionnaire but patients had a lower quality of life than controls (patients: 103.8 ± 18.3; controls: 113.4 ± 9.2; p < 0.001; Table 2). Patients showed significantly lower cognitive performance than controls on 5/8 of the following cognitive variables of interest: FCSRT, letter-number sequences, digit symbol test, TMT B test, Stroop test (Figure 1). The effect size was "medium" for all these tests (Figure 1). Different results between the two groups were identified in two of the six subtests of the M.I.N.I.: major depressive disorder (p < 0.01) and PTSD (p < 0.02) were more common in the patient group (Table 2).
We found a negative correlation between patients' COHb level and cognitive composite score (r = -0,42, p < 0,005) (Figure 2).
Figure 2.
Spearman correlation between COHb level and cognitive composite score.
BMC Neurol. 2014;14(153) © 2014 BioMed Central, Ltd.
