Vol.21, No. 2 Printed in Great Britain
International Journal of Epidemiology © International Epidemiological Association 1992
Motor Disability in Children in Three Birth Cohorts C RUMEAU ROUQUETTE, C DU MAZAUBRUN. A MLIKA AND L DEQUAE
Since its original description by Little1 cerebral palsy (CP) has been thought to be related to premature birth and perinatal hypoxia. In spite of recent progress in perinatal care, the trends in the prevalence of CP described by different authors have varied. It was a disappointment when Hagberg et al.1 showed that, after a decreasing incidence from 1959 to 1970, there was an increase in 1975-1978 in the population of Western Sweden. Analysing the data of an Australian register for the same period, Stanley showed that following the introduction of neonatal intensive care, total CP prevalence varied little amongst infants born between 1960 and 1982.3 The French situation offers a good opportunity for studying this problem for two important reasons: (1) the development of a national perinatal health care programme from 1972 to 1975, and (2) the decrease of preterm birthrates and low birthweight infant rates observed in the three nationwide surveys performed in 1972, 1976 and 1981." In 1975, the creation of medical and administrative centres collecting data on disabled children provided the possibility of registering disabled children from birth to 18 years. The aim of this paper is to describe the trend in the prevalence of motor disabilities amongst children born in 1972, 1976 and 1981, in order to assess whether it has changed in the
context of a decrease in preterm birth rate and neonatal mortality. MATERIALS AND METHODS This study was carried out in 14 geographical areas ('departements') located in the Southwest of France (Aquitaine), in the Eastern region (Lorraine), in the North (Picardie) and in the region around Paris (departements of Essonne, Val d'Oise and Seine et Marne). At the time of the 1982 census, these regions included a total of 405 160 residents for the 1972, 1976 and 1981 cohorts (Table 1). The above 'departements' were chosen because of the contrast between them. The perinatal mortality rate was very high in 1972 in Picardie (23.7 per 1000) and in Lorraine (23.1 per 1000), whereas the lowest rate was for the region around Paris (17.9 per 1000). The number of antenatal visits was higher in the Region around Paris and in Lorraine, but remained very low in Picardie. The use of electronic fetal monitoring was higher in Lorraine than in Aquitaine or Picardie.4 Since 1975, a register of disabled children has been kept by the Commissions for Special Education (CDES) set up in each French 'departement,' in order to help parents and direct children towards special education or hospital facilities. Two surveys5 were performed by the INSERM Unit for Epidemiological Research on Mother and Child (U149): in 1985-1986 for children
Unite 149 de I'lNSERM, 123 Bd de Port Royal, 75014 Paris, France.
359
Downloaded from http://ije.oxfordjournals.org/ at University of Bath Library & Learning Centre on June 10, 2015
Rumeau-Rouquette, C (Unite 149 de I'lNSERM, 123 Bd de Port Royal, 75014 Paris, France), du Mazaubrun C, Mlika A and Dequae L. Motor disability in children in three birth cohorts. International Journal of Epidemiology 1992; 21: 359-366. A systematic registration was carried out in 1985-1986 and 1989 in 14 French 'departements' in order to assess whether the prevalence rates of different components of motor disability (MD) in three different birth cohorts (1972, 1976 and 1981) had changed at a time when the preterm birth rate and neonatal mortality were decreasing and there was evidence of changing perinatal practice. A total of 1355 MD were registered amongst resident children born in 1972, 1976 and 1981 with a prevalence of 3.34 per 1000. The prevalence of the MD types due to different causes did not differ significantly amongst the three birth cohorts with the exception of an excess of hereditary and degenerative disease of the central nervous system (CNS) among children born in 1981. The prevalence of cerebral palsy (CP) remained stable in the three birth cohorts: it was 1.30, 1.06 and 1.08 per 1000 respectively, for children born in 1972, 1976 and 1981. The prevalence of pre- or perinatal-origin of other motor disabilities (OMD) and of CNS malformations did not differ amongst the three birth cohorts. The method of registration is discussed and the results are related to those of the French perinatal surveys performed in 1972, 1976 and 1981, which showed a decrease in preterm birthrate, an increase in perinatal care and a decrease in the mortality rate of higtvrisk infants.
360
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
TABLE 1 Total number of disabled children registered by CDES and other sources from 1975 to 1989 in 14 French departments
Year of birth
1976
152156
122660
2842 2475 271 96
1600 1400 131 69
1571 1441 87 43
6013 5316 489 208
Number of cases registered in hospitals and clinics, not registered by CDES Resident 8 Nonresident1" Not specified
28 24 4 0
57 48 9 0
108 101 3 4
193 173 16 4
Number of cases with unspecified origin
13
3
19
35
Number of parents refusing
71
35
28
134
Number of inhabitants (1982 census) Number of disabled children registered by CDES Resident 8 Nonresident1" Not specified
1981
Total
130 344 405 160
a Children resident in the same 'departement' of the CDES, hospital or clinics where they were recorded at the time of the survey. b not resident in the same 'departement.'
born in 1972 or 1976 and in 1989 for those born in 1981, using all the medical and administrative data collected by the CDES for all disabled children born in 1972, 1976 and 1981, both at admission and at followup. A total of 6013 cases were registered (Table 1). Only those children residing, at the time of the survey, in the same 'departement' of the CDES, hospitals or clinics where they were registered, were included in the study. The completeness of the reporting was checked by conducting an additional survey in psychiatric day treatment hospitals and general hospitals. It did not appear necessary to do so in specialized centres for disabled children, because the admission of children to these centres is through the CDES. Only 193 cases not registered by the CDES were identified through psychiatric day treatment hospitals and general hospitals. The number of parents who refused to be included in this survey was also low (134) (Table 1). Data were recorded by medical doctors in a standardized format including information on date and place of birth, sex of the child, parents' profession and place of residence, diagnosis of disability, probable aetiology, description of mental level and school per-
RESULTS Among the three cohorts of residents, 1355 MD children were registered: 780 boys (58%) and 561 girls
Downloaded from http://ije.oxfordjournals.org/ at University of Bath Library & Learning Centre on June 10, 2015
1972
formance, behavioural and emotional disorders, sensory defects and motor disabilities. In this investigation, motor disabilities (MD) are defined as all motor or tonicity abnormalities of any origin. The WHO International Classification of Diseases, Ninth Revision (ICD-9) was used for coding diagnoses. In the medical record, a brief description of symptoms was made indicating the presence of hemiplegia, quadriplegia, paraplegia, ataxy, athetosis and other motor disorders. The origin of the disability was recorded according to the medical record as genetic, pre- or perinatal (antenatal, delivery or neonatal) or postnatal. Those children with diagnosis of CP but without clinical symptoms of MD were excluded from the study (15 cases). Data verifications and analyses were performed by epidemiologists from INSERM (U149). The MD children were classified into five categories: - congenital malformation of the central nervous system (CNS) (ICD-9: 740, 741, 742) and multiple or other specified anomalies with CNS anomalies (759.7, 759.8); - hereditary and degenerative diseases of the CNS (ICD-9: 330 to 337); - cerebral palsy (CP) (ICD-9: 343) excluding malformation, hereditary and degenerative diseases of the CNS; - congenital malformation of the musculo-skeletal systems (ICD-9: 754, 755, 756) exclusive of the above groups; - other motor disabilities exclusive of the above groups (OMD). The prevalence rate was calculated by dividing the number of MD children whose parents were residents at the time of the survey in the same 'departements' as the CDES, hospitals or clinics where they were registered, by the number of inhabitants born in 1972, 1976 and 1981 recorded in the same'departements'during the 1982 census. According to the yearly estimates, the number of inhabitants at the time of the survey was not very different from that observed in 1982, and we preferred to rely on the most recent census data which were more precise than the yearly estimates. The numbers of live births in 1972, 1976 and 1981 were not used as denominators because they would not reflect the child population at the time of the survey, due to mortality and population movement in early childhood.
MOTOR DISABILITY IN CHILDREN
Main Pathogenig Groups Table 2 describes the proportion and the prevalence of the five pathogenic groups. Amongst the 185 CNSmalformed children there were 66 spina bifida with or without hydrocephalus, 49 microcephalus, 19 congenital hydrocephalus and 52 other or nonspecified malformations of CNS; two children had multiple malformations. Amongst the 52 other children with CNS malformations there were principally 17 reduction deformities of the brain, 16 unspecified anomalies of brain, spinal cord and nervous system and 10 multiple congenital anomalies. TABLE 2 Prevalence (per 1000) of the main pathogenic groups of children with motor disabilities (MD), cohorts 1972, 1976 and 1981
No.
Central nervous syslem (CNS) congenital malformations Hereditary and degenerative diseases of CNS Cerebral palsy Musculo-skeletal malformations Other motor disabilities (OMD) Total
Prevalence Proportion among MD (%) per 1000
185
14
0.46
127 469
9 35
0.31 1.16
111
8
0.27
463 1355
34 100
1.14 3.34
Musculo-skeletal malformations (111) included limb reduction (32) or other limb malformations (51), chondro or osteodystrophies (16) and other or nonspecified malformations (16). There were 4 children with multiple malformations.
The hereditary and degenerative diseases of the CNS (127) included cerebral degeneration (23 obstructive hydrocephalus and 14 others), other extrapyramidal diseases and abnormal movement disorders (15 symptomatic torsion dystonia and five others), spinocerebellar diseases (three Friedreich's ataxia, four hereditary spastic paraplegia, 11 primary cerebellar degeneration, 22 other cerebellar ataxia and 14 other spinocerebellar diseases), anterior horn cell diseases (11 Werdnig-Hoffman disease and three others) and others.2 A majority of the CP cases had a prenatal or perinatal origin (61%), although this was not determined for 29% of the cases and was described as postnatal for 10% of them. The remaining OMD group of 463 cases comprised 104 cases with a specified pre- or perinatal origin. Only 17 of these had a peripheral pathology such as brachial plexus paralysis. Pre- or perinatal CP and perinatal OMD were compared for birthweight and type of disability. There was an excess of low birthweight (
International Journal of Epidemiology © International Epidemiological Association 1992
Motor Disability in Children in Three Birth Cohorts C RUMEAU ROUQUETTE, C DU MAZAUBRUN. A MLIKA AND L DEQUAE
Since its original description by Little1 cerebral palsy (CP) has been thought to be related to premature birth and perinatal hypoxia. In spite of recent progress in perinatal care, the trends in the prevalence of CP described by different authors have varied. It was a disappointment when Hagberg et al.1 showed that, after a decreasing incidence from 1959 to 1970, there was an increase in 1975-1978 in the population of Western Sweden. Analysing the data of an Australian register for the same period, Stanley showed that following the introduction of neonatal intensive care, total CP prevalence varied little amongst infants born between 1960 and 1982.3 The French situation offers a good opportunity for studying this problem for two important reasons: (1) the development of a national perinatal health care programme from 1972 to 1975, and (2) the decrease of preterm birthrates and low birthweight infant rates observed in the three nationwide surveys performed in 1972, 1976 and 1981." In 1975, the creation of medical and administrative centres collecting data on disabled children provided the possibility of registering disabled children from birth to 18 years. The aim of this paper is to describe the trend in the prevalence of motor disabilities amongst children born in 1972, 1976 and 1981, in order to assess whether it has changed in the
context of a decrease in preterm birth rate and neonatal mortality. MATERIALS AND METHODS This study was carried out in 14 geographical areas ('departements') located in the Southwest of France (Aquitaine), in the Eastern region (Lorraine), in the North (Picardie) and in the region around Paris (departements of Essonne, Val d'Oise and Seine et Marne). At the time of the 1982 census, these regions included a total of 405 160 residents for the 1972, 1976 and 1981 cohorts (Table 1). The above 'departements' were chosen because of the contrast between them. The perinatal mortality rate was very high in 1972 in Picardie (23.7 per 1000) and in Lorraine (23.1 per 1000), whereas the lowest rate was for the region around Paris (17.9 per 1000). The number of antenatal visits was higher in the Region around Paris and in Lorraine, but remained very low in Picardie. The use of electronic fetal monitoring was higher in Lorraine than in Aquitaine or Picardie.4 Since 1975, a register of disabled children has been kept by the Commissions for Special Education (CDES) set up in each French 'departement,' in order to help parents and direct children towards special education or hospital facilities. Two surveys5 were performed by the INSERM Unit for Epidemiological Research on Mother and Child (U149): in 1985-1986 for children
Unite 149 de I'lNSERM, 123 Bd de Port Royal, 75014 Paris, France.
359
Downloaded from http://ije.oxfordjournals.org/ at University of Bath Library & Learning Centre on June 10, 2015
Rumeau-Rouquette, C (Unite 149 de I'lNSERM, 123 Bd de Port Royal, 75014 Paris, France), du Mazaubrun C, Mlika A and Dequae L. Motor disability in children in three birth cohorts. International Journal of Epidemiology 1992; 21: 359-366. A systematic registration was carried out in 1985-1986 and 1989 in 14 French 'departements' in order to assess whether the prevalence rates of different components of motor disability (MD) in three different birth cohorts (1972, 1976 and 1981) had changed at a time when the preterm birth rate and neonatal mortality were decreasing and there was evidence of changing perinatal practice. A total of 1355 MD were registered amongst resident children born in 1972, 1976 and 1981 with a prevalence of 3.34 per 1000. The prevalence of the MD types due to different causes did not differ significantly amongst the three birth cohorts with the exception of an excess of hereditary and degenerative disease of the central nervous system (CNS) among children born in 1981. The prevalence of cerebral palsy (CP) remained stable in the three birth cohorts: it was 1.30, 1.06 and 1.08 per 1000 respectively, for children born in 1972, 1976 and 1981. The prevalence of pre- or perinatal-origin of other motor disabilities (OMD) and of CNS malformations did not differ amongst the three birth cohorts. The method of registration is discussed and the results are related to those of the French perinatal surveys performed in 1972, 1976 and 1981, which showed a decrease in preterm birthrate, an increase in perinatal care and a decrease in the mortality rate of higtvrisk infants.
360
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
TABLE 1 Total number of disabled children registered by CDES and other sources from 1975 to 1989 in 14 French departments
Year of birth
1976
152156
122660
2842 2475 271 96
1600 1400 131 69
1571 1441 87 43
6013 5316 489 208
Number of cases registered in hospitals and clinics, not registered by CDES Resident 8 Nonresident1" Not specified
28 24 4 0
57 48 9 0
108 101 3 4
193 173 16 4
Number of cases with unspecified origin
13
3
19
35
Number of parents refusing
71
35
28
134
Number of inhabitants (1982 census) Number of disabled children registered by CDES Resident 8 Nonresident1" Not specified
1981
Total
130 344 405 160
a Children resident in the same 'departement' of the CDES, hospital or clinics where they were recorded at the time of the survey. b not resident in the same 'departement.'
born in 1972 or 1976 and in 1989 for those born in 1981, using all the medical and administrative data collected by the CDES for all disabled children born in 1972, 1976 and 1981, both at admission and at followup. A total of 6013 cases were registered (Table 1). Only those children residing, at the time of the survey, in the same 'departement' of the CDES, hospitals or clinics where they were registered, were included in the study. The completeness of the reporting was checked by conducting an additional survey in psychiatric day treatment hospitals and general hospitals. It did not appear necessary to do so in specialized centres for disabled children, because the admission of children to these centres is through the CDES. Only 193 cases not registered by the CDES were identified through psychiatric day treatment hospitals and general hospitals. The number of parents who refused to be included in this survey was also low (134) (Table 1). Data were recorded by medical doctors in a standardized format including information on date and place of birth, sex of the child, parents' profession and place of residence, diagnosis of disability, probable aetiology, description of mental level and school per-
RESULTS Among the three cohorts of residents, 1355 MD children were registered: 780 boys (58%) and 561 girls
Downloaded from http://ije.oxfordjournals.org/ at University of Bath Library & Learning Centre on June 10, 2015
1972
formance, behavioural and emotional disorders, sensory defects and motor disabilities. In this investigation, motor disabilities (MD) are defined as all motor or tonicity abnormalities of any origin. The WHO International Classification of Diseases, Ninth Revision (ICD-9) was used for coding diagnoses. In the medical record, a brief description of symptoms was made indicating the presence of hemiplegia, quadriplegia, paraplegia, ataxy, athetosis and other motor disorders. The origin of the disability was recorded according to the medical record as genetic, pre- or perinatal (antenatal, delivery or neonatal) or postnatal. Those children with diagnosis of CP but without clinical symptoms of MD were excluded from the study (15 cases). Data verifications and analyses were performed by epidemiologists from INSERM (U149). The MD children were classified into five categories: - congenital malformation of the central nervous system (CNS) (ICD-9: 740, 741, 742) and multiple or other specified anomalies with CNS anomalies (759.7, 759.8); - hereditary and degenerative diseases of the CNS (ICD-9: 330 to 337); - cerebral palsy (CP) (ICD-9: 343) excluding malformation, hereditary and degenerative diseases of the CNS; - congenital malformation of the musculo-skeletal systems (ICD-9: 754, 755, 756) exclusive of the above groups; - other motor disabilities exclusive of the above groups (OMD). The prevalence rate was calculated by dividing the number of MD children whose parents were residents at the time of the survey in the same 'departements' as the CDES, hospitals or clinics where they were registered, by the number of inhabitants born in 1972, 1976 and 1981 recorded in the same'departements'during the 1982 census. According to the yearly estimates, the number of inhabitants at the time of the survey was not very different from that observed in 1982, and we preferred to rely on the most recent census data which were more precise than the yearly estimates. The numbers of live births in 1972, 1976 and 1981 were not used as denominators because they would not reflect the child population at the time of the survey, due to mortality and population movement in early childhood.
MOTOR DISABILITY IN CHILDREN
Main Pathogenig Groups Table 2 describes the proportion and the prevalence of the five pathogenic groups. Amongst the 185 CNSmalformed children there were 66 spina bifida with or without hydrocephalus, 49 microcephalus, 19 congenital hydrocephalus and 52 other or nonspecified malformations of CNS; two children had multiple malformations. Amongst the 52 other children with CNS malformations there were principally 17 reduction deformities of the brain, 16 unspecified anomalies of brain, spinal cord and nervous system and 10 multiple congenital anomalies. TABLE 2 Prevalence (per 1000) of the main pathogenic groups of children with motor disabilities (MD), cohorts 1972, 1976 and 1981
No.
Central nervous syslem (CNS) congenital malformations Hereditary and degenerative diseases of CNS Cerebral palsy Musculo-skeletal malformations Other motor disabilities (OMD) Total
Prevalence Proportion among MD (%) per 1000
185
14
0.46
127 469
9 35
0.31 1.16
111
8
0.27
463 1355
34 100
1.14 3.34
Musculo-skeletal malformations (111) included limb reduction (32) or other limb malformations (51), chondro or osteodystrophies (16) and other or nonspecified malformations (16). There were 4 children with multiple malformations.
The hereditary and degenerative diseases of the CNS (127) included cerebral degeneration (23 obstructive hydrocephalus and 14 others), other extrapyramidal diseases and abnormal movement disorders (15 symptomatic torsion dystonia and five others), spinocerebellar diseases (three Friedreich's ataxia, four hereditary spastic paraplegia, 11 primary cerebellar degeneration, 22 other cerebellar ataxia and 14 other spinocerebellar diseases), anterior horn cell diseases (11 Werdnig-Hoffman disease and three others) and others.2 A majority of the CP cases had a prenatal or perinatal origin (61%), although this was not determined for 29% of the cases and was described as postnatal for 10% of them. The remaining OMD group of 463 cases comprised 104 cases with a specified pre- or perinatal origin. Only 17 of these had a peripheral pathology such as brachial plexus paralysis. Pre- or perinatal CP and perinatal OMD were compared for birthweight and type of disability. There was an excess of low birthweight (
