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Background: Several interventions to improve cognition in at risk children have been suggested. Identification of key variables predicting cognition is necessary to guide these interventions. This study was conducted to identify these variables in Ugandan children and guide such interventions. Methods: A cohort of 89 healthy children (45 females) aged 5 to 12 years old were followed over 24 months and had cognitive tests measuring visual spatial processing, memory, attention and spatial learning administered at baseline, 6 months and 24 months. Nutritional status, child’s educational level, maternal education, socioeconomic status and quality of the home environment were also measured at baseline. A multivariate, longitudinal model was then used to identify predictors of cognition over the 24 months. Results: A higher child’s education level was associated with better memory (p = 0.03), attention (p = 0.005) and spatial learning scores over the 24 months (p = 0.05); higher nutrition scores predicted better visual spatial processing (p = 0.002) and spatial learning scores (p = 0.008); and a higher home environment score predicted a better memory score (p = 0.03). Conclusion: Cognition in Ugandan children is predicted by child’s education, nutritional status and the home environment. Community interventions to improve cognition may be effective if they target multiple socioeconomic variables. © 2009 Bangirana et al.
The present study was conducted at Mulago Hospital, Kampala, Uganda. Participants were children aged 5 to 12 years recruited as healthy community controls for children with cerebral malaria and uncomplicated malaria taking part in prospective studies looking at the cognitive sequelae of cerebral malaria [21], [22]. They were recruited from the homes or neighbourhoods of children with cerebral malaria and uncomplicated malaria. All children had a medical history and physical examination done to ensure they were healthy at the time of recruitment. Children with a positive smear for malaria were treated with chloroquine and sulfadoxine/pyrimethamine (the first line antimalarial treatment at that time) while those with intestinal parasites were given appropriate antihelminthic medication as per the national health guidelines. Inclusion criteria were age 5–12 years with no acute illness and signed informed consent from the parent/guardian. Exclusion criteria were (1) a history of meningitis, encephalitis, or any brain disorder, including cerebral malaria; (2) a history of developmental delay; (3) prior admission to the hospital for malnutrition; (4) a history of chronic illness; (5) treatment for an acute illness during the preceding month and (6) admission for malaria during the preceding 6 months. Ethical approval for the study was granted by the Institutional Review Boards for Human Studies at Makerere University Faculty of Medicine, University Hospitals of Cleveland, Case Western Reserve University, Indiana Wesleyan University, University of Minnesota and the Uganda National Council for Science and Technology. Cognitive testing was done at baseline after physical examination with follow up testing at 6 months and 24 months by testers trained in the administration of the tests. Tests instructions from the test manuals were administered in the local language for children who did not understand English. Instructions were repeated when necessary in cases where the children failed to understand them. In some instances where the child still had difficultly comprehending, the mother or caretaker was asked to explain to the child. Visual spatial processing and memory were measured by the Kaufmann Assessment Battery for Children (KABC) [23] while spatial learning and attention were measured by the Tactual Performance Test (TPT) [24] and the Test of Variables of Attention (TOVA) [25] respectively. These tests have been validated in previous studies with children in Africa and South East Asia [12], [14], [16]. The two scales of the KABC that were administered were the Sequential Processing Scale where problems are solved by arranging the input in sequential order and the Simultaneous Processing Scale where problems are spatial, analogic or organisational and are solved by integrating the input simultaneously [23]. The TPT was administered to the blindfolded child who was required to place six wooden blocks into corresponding holes in a board. The child was first given the blocks to feel their shapes, then feel the holes in the board and their location. The child was given three trials lasting ten minutes each to place the blocks into the holes, the first trial was with the preferred hand, then the non preferred hand and finally with both hands. The TOVA was administered on a laptop where the child was asked to press a switch whenever the target stimulus (a small black box in the top position) appeared and not to press when the non target stimulus (a small black box in the bottom position) appeared. Outcome scores are inattention (failure to respond), commission (responding to non target), response time (time to respond to target), response time variability (variance in response times) and d’ prime (measure of response sensitivity). Visual spatial processing scores were derived from the Simultaneous Processing Scale of the KABC which comprises of Face Recognition, Gestalt Closure, Triangles, Matrix Analogies, Spatial Memory and Photo Series subscales while memory scores were derived from the Sequential Processing Scale which comprises of Hand Movements, Number Recall and Word Order subscales. Spatial learning was measured by the average time per block for the three trials on the TPT while attention was measured by the d prime score of the TOVA which is one’s ability to discriminate between the target and non target stimuli. While the child was doing the baseline cognitive tests, the parent/caregiver was asked about the quality of child’s home environment. The quality of the home environment was measured by the Middle Childhood Home Observation for the Measurement of the Environment (MC-HOME) [26]. The MC-HOME is used to assess the stimulation and learning opportunities offered by the child’s home environment. Studies using similar home evaluations have shown that the child’s home environment affects its cognitive development [13], [27]. The MC-HOME consists of eight subscales; Responsivity, Encouragement of maturity, Emotional climate, Learning materials and opportunities, Enrichment, Family companionship, Family integration and Physical environment. It has 59 items however item 40 ‘Family member has taken child to (or arranged for child to visit) a scientific, historical or art museum within past year’ was omitted because it was deemed not applicable to most of the children in the sample thus leaving 58 items for use in the study. This modified MC-HOME had an inter-item reliability of 0.85. Nutrition was assessed as in our previous studies [21], [22] by comparing weight for age to published norms [28] and obtaining a standardized z-score (Statistical Analysis System (SAS) release 9.1, SAS Institute, Inc., Cary, North Carolina). Socioeconomic status was assessed using a scoring instrument incorporating a checklist of material possessions, house structure, living density, food resources and access to electricity and clean water. Level of education of the child and mother were scored as follows: None = 0, Nursery = 1, Primary school grades 1−7 = 2−8, Secondary education = 9, Post-secondary school = 10. Children spend one to three years in nursery school (pre-primary) and seven years in primary school for classes Primary one to Primary seven (P1 to P7). The age of entry into nursery and primary varies because parents may delay to take children to school for various reasons. The Uganda government has a Universal Primary Education policy where all children are entitled to free primary education where schools are urged to promote children to the next class regardless of the performance. Six socioeconomic variables were obtained from the above assessments; quality of the home environment (MC-HOME score), nutritional status, maternal education level, child’s education level and socioeconomic status (SES) score. Data were entered into databases using FileMaker Pro 7 and analysed using Statistical Package for the Social Sciences (SPSS) version 11.0 and SAS 9.1. Raw cognitive test scores were log transformed to generate normal distributions, with a higher score for visual spatial processing, memory and attention reflecting a better score and a lower score for spatial learning reflecting a better score. Pearson’s correlations were run between test scores at baseline and 6 months and between 6 months scores and 24 months scores to determine the test-retest reliabilities of the tests. Similar correlations were also run between the socioeconomic factors to determine the relationships between them. A longitudinal mixed effects model [29] was used to study the effects of socioeconomic factors and other covariates (baseline age, gender, weight-for-age z-score, child’s education level, home score, social economic status (SES), and maternal education) on cognitive assessments, since the same cognitive assessments were performed at three time points. In the regression analyses, the predictor variable coefficients were calculated for each of the four outcome variables (log-transformed scores in the areas of visual spatial processing, learning, attention and working memory). Exponentiated coefficients represent the percent change in geometric mean per unit on the non-transformed scale of the predictor variable [30].
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