Abstract
Background
The incidence of neural tube defects (NTDs) is declining worldwide due to the implementation of folic acid supplementation programs. Such a program was implemented over 1996–97 in Newfoundland and Labrador, Canada. The geographical distribution of birth incidence was studied prior to and after the implementation of the program to identify regions of residual high incidence. Excess residual cases may potentially be due to genetic causes or incomplete supplementation program implementation.
Methods
Maternal place of residence for all provincial live birth and stillbirth notifications, provincial maternal-fetal medicine referrals, provincial rehabilitation referrals, and all provincial hospitals with NTDs or terminations for NTDs was obtained from 1975 to 2002 for near complete case ascertainment. Bayesian small area analysis was separately performed on cases from 1975–1996 and 1997–2002. The two time periods were compared.
Results
Birth incidence of NTDs was noted to decline after 1996, from 5.54/1000 live births to 1.08/1000 live births. 592 cases were found from 1975–1996 and 34 cases from 1997–2002. Relative risk of birth incidence was 0.93–1.18 (95% CI) for 1975–1996 and 0.97–1.02 for 1997–2002 after Bayesian smoothing. One region had an excess of residual cases greater than 34%.
Conclusions
The implications of this observation to the management of the public health initiative imply that overall response to the decrease in cases tends to be uniform across the province, with potentially one area of interest where extra efforts may be devoted.
MeSH terms: Neural tube defects, epidemiology, cluster analysis
Résumé
Contexte
L’incidence des anomalies du tube neural (ATN) diminue partout dans le monde depuis l’avènement des programmes de supplémentation en acide folique. Un tel programme a été mis en oeuvre à Terre-Neuve-et-Labrador (Canada) en 1996–1997. Nous avons étudié la répartition géographique des taux d’ATN à la naissance avant et après la mise en oeuvre du programme pour déterminer les régions où ces taux demeurent élevés. Les cas excédentaires résiduels pourraient avoir des causes génétiques ou s’expliquer par une mise en oeuvre incomplète du programme de supplémentation.
Méthode
Pour obtenir la quasi-totalité du nombre de cas, nous avons recueilli des données sur le lieu de résidence de la mère pour tous les avis de naissances vivantes et d’accouchements de morts-nés, les orientations en médecine materno-foetale, les orientations en réadaptation, ainsi que tous les hôpitaux ayant déclaré des ATN ou des interruptions de grossesse en raison d’ATN dans la province pour la période de 1975 à 2002. Nous avons effectué des analyses bayésiennes par petits territoires pour les cas de 1975 à 1996 et pour ceux de 1997 à 2002, puis comparé les deux périodes.
Résultats
L’incidence des ATN à la naissance a diminué après 1996, passant de 5,54 p. 1 000 naissances vivantes à 1,08 p. 1 000 naissances vivantes. Nous avons recensé 592 cas entre 1975 et 1996, et 34 cas entre 1997 et 2002. Le risque relatif d’incidence de ces naissances était de 0,93 à 1,18 (IC de 95 %) entre 1975 et 1996 et de 0,97 à 1,02 entre 1997 et 2002, après lissage bayésien. Dans une seule région, les cas excédentaires résiduels étaient supérieurs à 34 %.
Conclusions
Pour la gestion de l’initiative de santé publique que représente la supplémentation en acide folique, nos observations montrent que la réponse globale à la diminution des cas a tendance à être uniforme à l’échelle de la province, mais qu’il existe une région où il faudrait peut-être consacrer des efforts supplémentaires.
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