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H Dolk

Publications and source records attributed to H Dolk.

At least 37 records · Page 2Linked to original sources
PubMed1999

The role of the assessment of spatial variation and clustering in environmental surveillance of birth defects.

This paper discusses the role of small area spatial analysis of birth defects in environmental surveillance. Two approaches are reviewed: (1) the investigation of identified geographically localised potential environmental hazards, and (2) the detection of clustering. Examples are given where these 2 types of investigation have been used in the follow-up of individual clusters. Finally, it is argued that environmental surveillance, incorporating the 2 groups of spatial methods, should become a part of public health practice on both proactive and reactive basis.

Bias↗
PubMed1999

Evaluation of the impact of Chernobyl on the prevalence of congenital anomalies in 16 regions of Europe. EUROCAT Working Group.

BACKGROUND: Surveillance data from population-based congenital anomaly registers in 16 regions of Europe (mainly Western Europe) were analysed to assess the impact of the Chernobyl accident on the prevalence of selected congenital anomalies. METHODS: Three cohorts of pregnancies were defined: those exposed during the first month following Chernobyl (External Exposure Cohort), the first year (Total Exposure Cohort) and the two subsequent years (Control Cohort). Expected numbers of congenital anomalies in these cohorts were calculated from 1980-1985 baseline rates. Registries were grouped into three exposure categories according to first-year exposure estimates. RESULTS: There was no overall or dose-related increase in prevalence in the two exposed cohorts for Down's Syndrome, neural tube defects, other central nervous system defects or eye defects. There was a statistically significant overall 22% (95% CI: 13-31%) excess of Down's Syndrome in the Control Cohort, with no dose-response relationship. CONCLUSIONS: Chernobyl had no detectable impact on the prevalence of congenital anomalies in Western Europe, suggesting that in retrospect the widespread fear in the population about the possible effects of exposure on the unborn fetus was not justified. An increasing prevalence of Down's Syndrome in the 1980s, probably unrelated to Chernobyl, merits further investigation.

Abnormalities, Radiation-Induced↗
PubMed1999

Inequalities in low birth weight: parental social class, area deprivation, and "lone mother" status.

OBJECTIVE: To describe the extent of socioeconomic inequalities in low birth weight. To assess the relative benefits of measuring socioeconomic status by individual occupation, socioeconomic deprivation status of area of residence, or both, for describing inequalities and targeting resources. DESIGN: Analysis of birth registrations by registration status: joint compared with sole registrants ("lone mothers"), routinely recorded parental occupation (father's for joint registrants), and census derived enumeration district (ED) deprivation. SETTING: England and Wales, 1986-92. SUBJECTS: 471,411 births with coded parental occupation (random 10% sample) and birth weight. MAIN OUTCOME MEASURES: Proportion of low birth weight (< 2500 g) RESULTS: 34% of births to joint registrants in social classes IV and V, and 45% of births to sole registrants, were in the quintile of most deprived EDs. It was found that 6.8% of births were of low birth weight. Sole registrants were at higher risk (9.3% overall) than joint registrants, across all deprivation quintiles. For joint registrants, the socioeconomic risk gradient was similar by social class or area deprivation, but a greater gradient from 4.7% to 8.7% was found with combined classification. CONCLUSIONS: Up to 30% of low birth weight can be seen as being associated with levels of socioeconomic deprivation below that of the most affluent group, as measured in this study. Caution is needed when targeting interventions to high risk groups when using single indicators. For example, the majority of births to lone mothers and to joint registrants in social classes IV and V would be missed by targeting the most deprived quintile. There is a high degree of inequality in low birth weight according to social class, area deprivation and lone mother status. When using routinely recorded birth and census data, all three factors are important to show the true extent of inequalities.

Birth Weight↗
PubMed1999

Mortality among residents near cokeworks in Great Britain.

OBJECTIVES: To investigate whether residents near cokeworks have a higher standardised mortality than those further away, particularly from cardiovascular and respiratory causes, which may be associated with pollution from cokeworks. METHOD: Cross sectional small area study with routinely collected postcoded mortality data and small area census statistics. Populations within 7.5 km of 22 cokeworks in Great Britain, 1981-92. Expected numbers of deaths within 2 and 7.5 km of cokeworks, and in eight distance bands up to 7.5 km of cokeworks, were calculated by indirect standardisation from national rates stratified for age and sex and a small area deprivation index, and adjusted for region. Age groups examined were all ages, 1-14, 15-64, 65-74, > or = 75. Only the 1-14 and 15-44 age groups were examined for asthma mortality. RESULTS: There was a 3% (95% confidence interval (95% CI) 1% to 4%) excess of all deaths within 2 km of cokeworks, and a significant decline in mortality with distance from cokeworks. The excess of deaths within 2 km was slightly higher for females and elderly people, but excesses within 2 km and declines in risk with distance were significant for all adult age groups and both sexes. The size of the excess within 2 km was 5% (95% CI 3% to 7%) for cardiovascular causes, 6% (95% CI 3% to 9%) for ischaemic heart disease, and 2% (95% CI -2% to 6%) for respiratory deaths, with significant declines in risk with distance for all these causes. There was a non-significant 15% (95% CI -1% to 101%) excess in asthma mortality in the 15-44 age group. There were no significant excesses in mortality among children but 95% CIs were wide. Within 2 km of cokeworks, the estimated additional excess all cause mortality for all ages combined related to region and mainly to the greater deprivation of the population over national levels was 12%. CONCLUSIONS: A small excess mortality near cokeworks as found in this study is plausible in the light of current evidence about the health impact of air pollution. However, in this study the effects of pollution from cokeworks, if any, are outweighed by the effects of deprivation on weighed by the effects of deprivation on mortality near cokeworks. It is not possible to confidently exclude socioeconomic confounding or biases resulting from inexact population estimation as explanations for the excess found.

Adolescent↗
PubMed1998

Geographical variation in anophthalmia and microphthalmia in England, 1988-94.

OBJECTIVE: To investigate the geographical variation and clustering of congenital anophthalmia and microphthalmia in England, in response to media reports of clusters. DESIGN: Comparison of pattern of residence at birth of cases of anophthalmia and microphthalmia in England in 1988-94, notified to a special register, with pattern of residence of all births. Three groups studied included all cases, all severe cases, and all severe cases of unknown aetiology. OUTCOME MEASURES: Prevalence rates of anophthalmia and microphthalmia by region and district, and by ward population density and socioeconomic deprivation index of enumeration district grouped into fifths. Clustering expressed as the tendency for the three nearest neighbours of a case to be more likely to be cases than expected by chance, or for there to be more cases within circles of fixed radius of a case than expected by chance. RESULTS: The overall prevalence of anophthalmia and microphthalmia was 1.0 per 10 000 births. Regional and district variation in prevalence did not reach statistical significance. Prevalence was higher in rural than urban areas: the relative risk in the group of wards of lowest population density compared with the most densely populated group was 1.79 (95% confidence interval 1.15 to 2.81) for all cases and 2.37 (1.38 to 4. 08) for severe cases. There was no evidence of a trend in risk with socioeconomic deprivation. There was very little evidence of localised clustering. CONCLUSIONS: There is very little evidence to support the presence of strongly localised environmental exposures causing clusters of children to be born with anophthalmia or microphthalmia. The excess risk in rural areas requires further investigation.

Anophthalmos↗
PubMed1998

Risk of congenital anomalies near hazardous-waste landfill sites in Europe: the EUROHAZCON study.

BACKGROUND: Waste-disposal sites are a potential hazard to health. This study is a multicentre case-control study of the risk of congenital anomalies associated with residence near hazardous-waste landfill sites in Europe. METHODS: We used data from seven regional registers of congenital anomalies in five countries. We studied 1089 livebirths, stillbirths, and terminations of pregnancy with non-chromosomal congenital anomalies and 2366 control births without malformation, whose mothers resided within 7 km of a landfill site; 21 sites were included. A zone within 3 km radius of each site was defined as the "proximate zone" of most likely exposure to teratogens. FINDINGS: Residence within 3 km of a landfill site was associated with a significantly raised risk of congenital anomaly (295 cases/511 controls living 0-3 km from sites, 794/1855 living 3-7 km from sites; combined odds ratio 1.33 [95% CI 1.11-1.59], adjusted for maternal age and socioeconomic status). There was a fairly consistent decrease in risk with distance away from the sites. A significantly raised odds ratio for residence within 3 km of a landfill site was found for neural-tube defects (odds ratio 1.86 [1.24-2.79]), malformations of the cardiac septa (1.49 [1.09-2.04]), and anomalies of great arteries and veins (1.81 [1.02-3.20]). Odds ratios of borderline significance were found for tracheo-oesophageal anomalies (2.25 [0.96-5.26]), hypospadias (1.96 [0.98-3.92]), and gastroschisis (3.19 [0.95-10.77]). There was little evidence of differences in risk between landfill sites but power to detect such differences was low. INTERPRETATION: This study shows a raised risk of congenital anomaly in babies whose mothers live close to landfill sites that handle hazardous chemical wastes, although there is a need for further investigation of whether the association of raised risk of congenital anomaly and residence near landfill sites is a causal one. Apparent differences between malformation subgroups should be interpreted cautiously.

Case-Control Studies↗
PubMed1998

Does the Child Health Computing System adequately identify children with cerebral palsy?

BACKGROUND: This paper assesses the usefulness of the Child Health Computing System as a source of information about children with cerebral palsy. METHODS: A comparative survey of information held on the Child Health Computing System (CHCS) and the Northern Ireland Cerebral Palsy Register (NICPR) in one Health and Social Services Board in Northern Ireland was carried out. The sample comprised children with cerebral palsy aged 5-9 years. RESULTS: Of the 135 cases recorded on the NICPR, 47 per cent were not found on the CHCS; the majority of these children had no computer record of any medical diagnosis. Of the 82 cases recorded on the CHCS, 10 (12 per cent) were not found on the NICPR; five of these cases (6 per cent) were found on follow-up not to have CP. CONCLUSIONS: Unless improvements are made in case ascertainment, case validation and recording activities, the evidence suggests that the CHCS will not be able to provide the same quality of information for needs assessment and surveillance of very low birthweight infants in relation to cerebral palsy as is provided by a specialist case register.

Cerebral Palsy↗
PubMed1998

Compiling a national register of babies born with anophthalmia/microphthalmia in England 1988-94.

AIM: To describe the prevalence of anophthalmia/microphthalmia in babies born in England 1988-94, as well as their overall survival, and the incidence of associated eye and non-eye malformations; to determine the usefulness of different sources of medical and health service information for establishing a retrospective register of anophthalmia/microphthalmia. METHODS: Multiple sources for initial (retrospective) case ascertainment were surveyed, followed by questionnaires to clinicians to establish severity, associated malformations, and aetiology for England, 1988-94. The population surveyed was all births in England for this time period (4,570,350 births). Cases included live births, stillbirths, or terminations after prenatal diagnosis of congenital anomaly, with anophthalmia/microphthalmia, with or without other malformations and syndromes. Trisomy 13 was subsequently excluded. RESULTS: The proportion of cases notified by any one information source was not more than 26% (Office for National Statistics Register 22%, paediatricians 26%, district sources 25%). Sixty nine per cent of cases (51% of severe cases) were notified by only one source. A total of 449 cases were reported, prevalence 1.0 per 10,000 births. The prevalence was stable over time, although the proportion notified by clinicians rose in more recent years. Thirty four per cent of affected babies had mild microphthalmia. Of those with severe anophthalmia/microphthalmia, 51% were bilateral, other eye malformations were present in 72%, non-eye malformations in 65%, and a "known aetiology" was attributed in 22%. Three quarters of those severely affected survived infancy. CONCLUSIONS: Despite high response rates from the sources of information contacted, the lack of duplication between sources indicates the difficulties of retrospective ascertainment and the need for multiple sources when establishing a register. Anophthalmos/microphthalmos is usually associated with other malformations. Most cases are of unknown aetiology.

Abnormalities, Multiple↗
PubMed1997

Are omphalocele and neural tube defects related congenital anomalies?: Data from 21 registries in Europe (EUROCAT).

We have analyzed the association between omphalocele and neural tube defects (O/NTD) previously reported in epidemiological studies of EUROCAT registry data [Dolk et al., 1991; Calzolari et al., 1995]. By examining differences in prevalence between the United Kingdom and Ireland (UKI) and Continental Europe and Malta (CEM) and differences in sex ratio, the possible etiopathogenetic differences between O/NTD association and omphalocele without NTD and NTD without omphalocele were investigated. The distribution of O/NTD cases according to NTD site in the two geographic areas shows in the UKI a tendency for omphalocele to associate with anencephaly/spina bifida and with anencephaly. In CEM centers, these types of NTD are much rarer. The pattern of other anomalies occurring in combination with O/NTD association in the same babies was also analysed.

Birth Rate↗
PubMed1997

Cancer incidence near radio and television transmitters in Great Britain. I. Sutton Coldfield transmitter.

A small area study of cancer incidence in 1974-1986 was carried out to investigate an unconfirmed report of a "cluster" of leukemias and lymphomas near the Sutton Coldfield television (TV) and frequency modulation (FM) radio transmitter in the West Midlands, England. The study used a national database of postcoded cancer registrations, and population and socioeconomic data from the 1981 census. Selected cancers were hematopoietic and lymphatic, brain, skin, eye, male breast, female breast, lung, colorectal, stomach, prostate, and bladder. Expected numbers of cancers in small areas were calculated by indirect standardization, with stratification for a small area socioeconomic index. The study area was defined as a 10 km radius circle around the transmitter, within which 10 bands of increasing distance from the transmitter were defined as a basis for testing for a decline in risk with distance, and an inner area was arbitrarily defined for descriptive purposes as a 2 km radius circle. The risk of adult leukemia within 2 km was 1.83 (95% confidence interval 1.22-2.74), and there was a significant decline in risk with distance from the transmitter (p = 0.001). These findings appeared to be consistent over the periods 1974-1980, 1981-1986, and were probably largely independent of the initially reported cluster, which appeared to concern mainly a later period. In the context of variability of leukemia risk across census wards in the West Midlands as a whole, the Sutton Coldfield findings were unusual. A significant decline in risk with distance was also found for skin cancer, possibly related to residual socioeconomic confounding, and for bladder cancer. Study of other radio and TV transmitters in Great Britain is required to put the present results in wider context. No causal implications can be made from a single cluster investigation of this kind.

Adolescent↗
PubMed1997

Cancer incidence near radio and television transmitters in Great Britain. II. All high power transmitters.

A small area study of cancer incidence, 1974-1986, near 20 high power television (TV) and frequency modulation (FM) radio transmitters in Great Britain was carried out to place in context the findings of an earlier study around the Sutton Coldfield transmitter. The national database of postcoded cancer registrations was used with population and socioeconomic data from the 1981 census. Cancers examined were adult leukemias, skin melanoma, and bladder cancer, following the findings in the earlier study of significant declines in risk of these cancers with distance from the Sutton Coldfield transmitter. Childhood leukemia and brain cancer were also examined. Statistical analysis was performed for all transmitters combined, four overlapping groups of transmitters defined by their transmission characteristics, and for all transmitters separately. There were 3,305 adult leukemia cases from 0-10 km (observed/expected (O/E) ratio = 1.03, 95% confidence interval (CI) 1.00-1.07). A decline in risk of adult leukemia was found for all transmitters combined (p = 0.05), two of the transmitter groups, and three of the single transmitters; for all transmitters combined, observed excess risk was no more than 15% at any distance up to 10 km, and there was no observed excess within 2 km of transmitters (O/E ratio = 0.97, 95% CI 0.78-1.21). For childhood leukemia and brain cancer, and adult skin melanoma and bladder cancer, results were not indicative of a decline in risk with distance from transmitters. The magnitude and pattern of risk found in the Sutton Coldfield study did not appear to be replicated. The authors conclude that the results at most give no more than very weak support to the Sutton Coldfield findings.

Adolescent↗
PubMed1997

Small-area study of the incidence of neoplasms of the brain and central nervous system among adults in the West Midlands region, 1974-86. Small Area Health Statistics Unit.

This small-area study of incidence of cancers of the brain and central nervous system found evidence of trend (P = 0.02) of cancer risk with deprivation (8% higher risk in affluent areas), but no significant association with urban-rural status. Results were not indicative of a strong geographically determined risk at small-area level.

Adolescent↗
PubMed1995

Omphalocele and gastroschisis in Europe: a survey of 3 million births 1980-1990. EUROCAT Working Group.

A total of 732 cases of omphalocele and 274 cases of gastroschisis was registered in 21 regional registers in Europe (EUROCAT registers) during the period 1980-1990. The total prevalence rates were 2.52 per 10,000 for omphalocele and 0.94 per 10,000 for gastroschisis. There was significant heterogeneity in total prevalence rates among regions for omphalocele. Consistently higher than average total prevalence rates of omphalocele were found in the five centers of the British Isles. This was in large part linked to the association between omphalocele and neural tube defects. A significant female excess among the cases of omphalocele associated with neural tube defects, in comparison with an insignificant male excess for other cases of omphalocele, was observed. Geographical differences in the total prevalence of gastroschisis are partly explained by differences in maternal age distributions in the populations surveyed. Omphalocele was an isolated malformation in 46% of cases; gastroschisis was isolated in 79% of cases. The average birthweight and gestational age of both isolated and multiply malformed cases of both omphalocele and gastroschisis were low, especially for multiply malformed cases, and to a greater extent for isolated gastroschisis than for isolated omphalocele. Prenatal diagnosis leading to termination of pregnancy was reported in 33.2% of omphalocele and in 26.5% of gastroschisis cases, demonstrating the considerable impact of current prenatal screening programs. On the basis of clinical manifestations, epidemiologic characteristics, and the presence and type of additional malformations, omphalocele and gastroschisis can be considered heterogeneous conditions.

Abdominal Muscles↗
PubMed1995

A standardisation approach to the control of socioeconomic confounding in small area studies of environment and health.

OBJECTIVE: To assess how effectively a routine adjustment can be made for socio-economic confounding in small area studies of environment and health using indirect standardisation and small area deprivation indices, including analysis of the appropriate size of population unit on which to base the deprivation index and the importance of region and urban/rural status as axes of stratification. METHODS: Standardised morbidity ratios were calculated for cancers in Great Britain for 1981 and standardised mortality ratios for all cause mortality in Great Britain between 1982 and 1985. Deprivation indices were calculated for enumeration districts and wards from 1981 small area census statistics. Cancers and deaths were allocated to enumeration districts via their postcode. Standardised morbidity and mortality ratios were calculated by quintile of enumeration district according to the deprivation index. Standardised mortality ratios were further analysed by deprivation of ward, region, and urban/rural status. RESULTS: Strong relationships were found between all cause mortality and the incidence of selected cancers and deprivation quintile-there was up to a twofold difference in lung cancer incidence between the highest and lowest quintile. The deprivation index can be used to measure gradients of deprivation according to the distance from industrial sites. The deprivation index for enumeration districts showed similar discrimination of mortality as the index forwards. There is some interaction between deprivation and region in their effect on the standardised mortality ratios, leading to a small bias in the estimation of expected numbers if this is not taken into account. The relationship between deprivation, urban/rural status, and mortality is complex and confounded by region, but mortality tends to be higher in urban than in rural areas within quintiles of deprivation. DISCUSSION: Whether calculated for enumeration districts or wards, the main problems in the interpretation of the deprivation index may be its limited correlation with the risk factors of interest and its concentration on present rather than past socioeconomic status. Indirect standardisation based on stratification for deprivation and other variable involves a trade off between bias and precision in determining the fineness and the number of axes of stratification. Some bias may occur due to interaction between region and deprivation and the effects of urban/rural status. Complementary approaches including modeling and proportional mortality or morbidity analyses may be needed and the possibility of residual socioeconomic confounding must always be considered. CONCLUSION: There is potential for important socioeconomic confounding in small area studies of environmental pollution and health where the health outcome under examination has a strong relationship to socioeconomic status and where the putative excess risk due to pollution may be small. One method of controlling for confounding is to use an ecological measurement of deprivation in small areas, and to adjust for deprivation by indirect standardisation. However, residual socioeconomic confounding can be expected, which may seriously complicate the interpretation of small area studies.

Adolescent↗
PubMed1995

Cancer incidence and mortality near the Baglan Bay petrochemical works, South Wales.

OBJECTIVES: To study incidence and mortality of leukaemias, cancer of the larynx, and other cancers near the petrochemical plant at Baglan Bay, in response to local concerns of an alleged cluster of cancers in the vicinity. METHODS: This is a small area study of cancer incidence, 1974-84 and of mortality, 1981-91 based on the national postcoded data held by the Small Area Health Statistics Unit and with population and socioeconomic data from the 1981 census. The study is centred on BP Chemicals Ltd, Baglan Bay, Port Talbot, West Glamorgan, South Wales and includes a general population sample of 115,721 people (1981 census) living within 7.5 km of the plant. Cancer incidence and mortality for all cancers, leukaemias, and cancer of the larynx were examined within 7.5 km and 3 km of the plant, and tests for decline in risk of these cancers with distance from the plant were carried out. Mortality from several other cancers possibly associated with the petrochemical industry was also studied. RESULTS: There were 5417 incident cancer cases and 2458 cancer deaths within 7.5 km of the plant during the periods of study. There was an 8% excess incidence of all cancers within 7.5 km, and a 24% excess of cancer of the larynx, consistent with a general excess of these cancers in West Glamorgan, but no apparent decline in incidence with distance from the plant, nor excess mortality. There was also no evidence of decline in leukaemia incidence or mortality with distance, at all ages or in children. Among the other causes included in the mortality study, there was an excess of multiple myeloma within 7.5 km, especially among women, and a significant decline in mortality from non-Hodgkin's lymphomas although there was no excess overall within 7.5 km. CONCLUSIONS: The apparent excess incidence of all cancers and cancer of the larynx within 7.5 km of the BP Chemical Ltd works was consistent with an excess more generally in West Glamorgan, possibly related, at least to some extent, to cancer registration in Wales. There was no excess mortality from these cancers. The results for multiple myeloma and especially non-Hodgkin's lymphomas may have been chance findings in view of the multiple tests of significance carried out in the study. A study of lymphatic and haematopoietic cancers near oil refineries in Great Britain is to be undertaken that will help put the findings of the present study in wider context.

Adolescent↗