The epidemiology of mental and behavioural disorders is considered in comparison with spina bifida, chromosomal anomalies and brain tumours. Descriptive epidemiology is important not only in assessing the frequency of...
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The epidemiology of mental and behavioural disorders is considered in comparison with spina bifida, chromosomal anomalies and brain tumours. Descriptive epidemiology is important not only in assessing the frequency of neurodevelopmental disorders, thereby aiding planning of service provision, but also because variations by geographical area, over time, and by personal characteristics provide clues regarding etiology. The value of the latter application is exemplified by research on spina bifida and other neural tube defects (NTDs). The descriptive epidemiology of mental and behavioural disorders has been less investigated. The descriptive epidemiology of NTDs suggested that diet might be of etiological importance. Analytical epidemiologic investigation proceeded by testing dietary hypotheses in case-control and cohort studies. Subsequently, folate supplementation was shown to reduce recurrence risk in a randomized controlled trial. The analytical epidemiology of other neurodevelopmental disorders is less well understood. Study design issues are discussed in relation to mental and behavioural disorders. (C) 2000 Harcourt Publishers Ltd.
Neural tube defects (NTDs) are multifactorial in their etiology, having both genetic and environmental factors contributing to their development. Recent evidence demonstrates that periconceptional supplementation of t...
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Neural tube defects (NTDs) are multifactorial in their etiology, having both genetic and environmental factors contributing to their development. Recent evidence demonstrates that periconceptional supplementation of the maternal diet with a multivitamin containing folic acid significantly reduces the occurrence and recurrence risk for having a pregnancy complicated by NTDs. Unfortunately, the mechanism underlying the beneficial effects of folic acid remains unknown. NTD surveillance data from the Texas-Mexico border show that the high NTD rate (28/10,000 live births) noted during the 1990-1991 Cameron county NTD cluster was superimposed on a background Cameron county NTD rate (16/10,000 five births) which is considerably higher than that generally noted in the United States (8-10/10,000 live births). These data suggest that genetic factors as well as transient environmental factors may contribute to the etiology of the NTDs. Furthermore, clinical and experimental evidence imply that allelic forms of genes involved with folate metabolism and/or transport may explain some of the observed variation in the NTD rates found across different populations. Two folate pathway genes were selected for evaluation in this study. The loci investigated included two known alleles of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, as well as the promoter region of the folate receptor-alpha (FR-alpha) gene. Odds ratios (ORs) for the C677T polymorphism in the MTHFR gene were 1.8 (CI 0.47-6.8) for heterozygosity and 1.8 (CI 0.35-9.4) for homozygosity for the mutant 677T allele, relative to wildtype homozygotes. The odds ratio for the heterozygosity for the A1298C polymorphism in the same gene was 1.1 (CI 0.09-14). No individuals homozygous for the 1298C allele were observed. The OR for heterozygosity of FR-cy gene polymorphisms detected at nucleotide 762 and at nucleotides 610/631 was 1.4 and 0.7, respectively. Neither of the FR-alpha polymorphisms was observed in the homozyg
The birth incidence of neural tube defects (NTDs) in South Africa is threefold to sixfold higher in rural compared with urban blacks. We investigated whether folate deficiency and aberrant homocysteine metabolism coul...
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The birth incidence of neural tube defects (NTDs) in South Africa is threefold to sixfold higher in rural compared with urban blacks. We investigated whether folate deficiency and aberrant homocysteine metabolism could explain the high NTD incidence in rural black populations, Plasma folate and total homocyst(e)ine (tHcy) concentrations were determined in apparently healthy rural black women (n = 107), rural black women with a history of pregnancy complicated by NTDs (n = 54), and urban blacks (n = 101). Methionine load tests were performed on the 54 women with a history of NTD-affected pregnancy and 54 controls matched for age and body mass. The presence of the 677C --> T mutation in the methylene tetrahydrofolate reductase (MTHFR) gene was investigated in both groups by a polymerase chain reaction (PCR) of genomic DNA and Hinfl digestion of the PCR product. Apparently healthy urban black women (n = 101) had a lower (P <.001) plasma folate concentration compared with rural black women (n = 107). Women with a history of NTD-affected pregnancy did not differ significantly from controls with respect to plasma folate, fasting homocyst(e)ine, methionine, and the post-methionine load increase in plasma homocyst(e)ine, More than 50% of both of the latter groups had a post-methionine load increase in plasma tHcy less than the fifth percentile as observed in a healthy white control group. No homozygotes for the 677C --> T mutation in the MTHFR gene were found in black mothers with NTD-affected offspring or controls. It is concluded that black urbanization is characterized by a diminished folate status that is paradoxically associated with a lower NTD birth incidence. Homozygosity for the 677C --> T mutation in the gene coding for MTHFR does not constitute a genetic risk factor for NTDs in blacks. No aberrant homocysteine metabolism could be demonstrated in black women with NTD-affected pregnancies. Copyright (C) 1999 by W.B. Saunders Company.
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