Gillian M. Raab

Influence of blood lead on the ability and attainment of children in Edinburgh.

The effect of blood-lead on childrens ability and attainment was investigated in a sample of 855 boys and girls aged 6-9 years from eighteen primary schools within a defined area of central Edinburgh. The geometric mean blood-lead value was 10.4 micrograms/dl. In a stratified subsample, 501 children completed individual tests of cognitive ability and educational attainment from the British Ability Scales (BAS). An extensive home interview with a parent was also done. Multiple regression analyses showed a significant negative relation between log blood-lead and BAS combined score, number skills, and word reading when thirty-three possible confounding variables were taken into account. There was a dose-response relation between blood-lead and test scores, with no evidence of a threshold. The size of the effect was small compared with that of other factors. Lead at low levels of exposure probably has a small harmful effect on the performance of children in ability and attainment tests.

Does Widowhood Increase Mortality Risk? Testing for Selection Effects by Comparing Causes of Spousal Death

Background: We consider whether widowhood increases mortality risk. Although commonly observed, this “widowhood effect” could be due to selection effects, as married couples share various characteristics related to the risk of death. We therefore consider the widowhood effect by various causes of spousal death; some causes of death are correlated with shared characteristics in couples, while others are not. Methods: Using data from the Scottish Longitudinal Study, we compare outcomes for men and women by the causes of death of their spouse, controlling for a range of individual- and household-level characteristics. Results: The widowhood effect in these data is greater than has been found in other recent studies, with adjusted hazard ratios of 1.40 (95% confidence interval = 1.33–1.47) for men and 1.36 (1.30–1.44) for women. The risk is highest shortly after widowhood, but remains raised for at least 10 years. There was little evidence that these hazard ratios differed by any classification of the cause of death of the spouse, but interactions were found for those with pre-existing illness or other risk factors. The hazard ratios for widowhood were lower for persons with preexisting risks. Conclusions: Our analysis of the widowhood effect uses 3 methods of classifying the causes of spousal death in an attempt to control for potential selection effects. Our results are highly consistent and suggest that this is a causal effect, rather than a result of selection.

DataSHIELD: taking the analysis to the data, not the data to the analysis

Background: Research in modern biomedicine and social science requires sample sizes so large that they can often only be achieved through a pooled co-analysis of data from several studies. But the pooling of information from individuals in a central database that may be queried by researchers raises important ethico-legal questions and can be controversial. In the UK this has been highlighted by recent debate and controversy relating to the UK’s proposed ‘care.data’ initiative, and these issues reflect important societal and professional concerns about privacy, confidentiality and intellectual property. DataSHIELD provides a novel technological solution that can circumvent some of the most basic challenges in facilitating the access of researchers and other healthcare professionals to individual-level data. Methods: Commands are sent from a central analysis computer (AC) to several data computers (DCs) storing the data to be co-analysed. The data sets are analysed simultaneously but in parallel. The separate parallelized analyses are linked by non-disclosive summary statistics and commands transmitted back and forth between the DCs and the AC. This paper describes the technical implementation of DataSHIELD using a modified R statistical environment linked to an Opal database deployed behind the computer firewall of each DC. Analysis is controlled through a standard R environment at the AC. Results: Based on this Opal/R implementation, DataSHIELD is currently used by the Healthy Obese Project and the Environmental Core Project (BioSHaRE-EU) for the federated analysis of 10 data sets across eight European countries, and this illustrates the opportunities and challenges presented by the DataSHIELD approach. Conclusions: DataSHIELD facilitates important research in settings where: (i) a co-analysis of individual-level data from several studies is scientifically necessary but governance restrictions prohibit the release or sharing of some of the required data, and/or render data access unacceptably slow; (ii) a research group (e.g. in a developing nation) is particularly vulnerable to loss of intellectual property—the researchers want to fully share the information held in their data with national and international collaborators, but do not wish to hand over the physical data themselves; and (iii) a data set is to be included in an individual-level co-analysis but the physical size of the data precludes direct transfer to a new site for analysis.

Children's blood lead and exposure to lead in household dust and water: a basis for an environmental standard for lead in dust

Good quantitative evidence on the role of lead in household dust as a source of exposure to children has been lacking. A study of 495 children in Edinburgh, Scotland shows a significant relationship between lead in dust vacuumed from the floors of the childrens homes and their blood lead levels. A multiple regression analysis incorporating drinking water and household dust estimates that a 1,000 micrograms g-1 increase in dust lead concentration would increase blood lead by 1.9 micrograms dl-1, for a child with the median population blood lead of 10.1 micrograms dl-1. Dust lead concentration is a more useful predictor of blood lead than lead loading. The sanding or blow-lamp stripping of old paint is found to be an important source of the higher household dust lead concentrations. Finally, the dust lead-blood lead relationship is used to derive a standard for lead in house dust, as no such standard exists for this exposure route.

Exit, choice and loyalty: the impact of parental choice on admissions to secondary schools in Edinburgh and Dundee

This paper analyses the effects of parental choice on first‐year admissions to 20 non‐denominational secondary schools in Edinburgh and ten in Dundee. Although Dundee is a more working‐class city than Edinburgh, the take‐up of placing requests in Dundee was somewhat higher than in Edinburgh. There was a substantial increase in the take‐up of placing requests in both cities over the period 1982‐85 (from 13.5% to 21.0% of the S1 intake in Edinburgh and from 14.0% to 23.7% in Dundee). In each city, there was evidence of bandwagon effects ‐ some schools gained an increasing proportion of their S1 intakes through parental choice while others lost an increasing proportion of their intakes for this reason. However, the imposition of intake limits on three of the ‘most popular’ secondary schools in Edinburgh not only decreased the number of requests for those schools but also reduced the outflows from the ‘least popular’ schools. The paper uses logistic regression to calculate the effects of extra travelling dist...

The accuracy of simple ordinal scoring of tooth attrition in age assessment

Tooth wear is frequently used as a method of ageing skeletal remains. Fundamental to this method is the ability to measure the amount of tooth wear. The Brothwell chart based on the Miles method of ageing, uses simple ordinal scoring and is frequently used by archeologists. The purpose of the present investigation was to evaluate the accuracy of simple ordinal scoring in recording tooth wear and ageing skulls. A group of Chinese skulls of known age at death was used. The age range was from 16 to 60 years. A single score per molar tooth was used to record occlusal wear. The data were analysed by regression methods using BMDP statistical software. The results showed that molar tooth wear continues throughout the life of the individual. The first molar teeth wear significantly more quickly than do second molar teeth. Use of a simple ordinal score method for recording wear gives an inaccurate estimate of an individual skulls age at death with a very wide 95% confidence interval.

THE POTENTIAL OF MID-TRIMESTER MATERNAL PLASMA ALPHA-FETOPROTEIN MEASUREMENT IN PREDICTING INFANTS OF LOW BIRTH WEIGHT

Maternal plasma alpha‐fetoprotein (AFP) was measured at mid‐trimester in 113 women who subsequently were delivered of a singleton liveborn infant weighing less than 2·5 kg and in 113 matched controls whose infants weighed more than 2·5 kg. Plasma AFP levels were significantly higher in the subjects than in the controls, while 10 of the subjects and only 3 of the controls had values above 2·0 times the median. The higher AFP concentrations were seen both in pregnancies in which the outcome was a small premature infant and in those in which it was a small‐for‐dates baby.

Factors influencing lead concentrations in shed deciduous teeth

Data collected for the Edinburgh Lead Study have been used to investigate lead concentrations in childrens naturally shed deciduous teeth. A within-child multiple-regression analysis has shown that the upper jaw has a higher concentration of lead than the lower, and that there is a gradient of decreasing concentration from the front to the back of the mouth. Even after the effects of jaw and tooth type have been allowed for, the concentration is still found to be negatively correlated with the weight of the tooth and with the age at which the tooth was shed. No statistically significant effects could be attributed to caries, fillings, or the incomplete resorption of roots. A single-valued index of tooth lead has been derived for each child, taking into account the fact that children gave different types of teeth.

Lead from dust and water as exposure sources for children

Data from the Edinburgh Lead Study are used to estimate the respective contributions of water and dust lead to blood lead in 6–9 year old children. Both sources are significantly related to blood lead. An exposure of 100 μg/l in kitchen cold water is estimated to be equivalent to 2700 μg/g of lead in dust. In this population water is a more important source of lead than dust for the bulk of the population.

The variability of lead in dusts within the homes of young children.

The variability of household dust lead concentration and loadings over the period of about a year has been examined in 10 homes. The overall uncertainty on a single sample is ± 65% for lead concentration and ± 81% for lead loading. Redecoration involving electric sanding and/or blow lamp preparation of painted surfaces is the major cause of variation in lead levels. The effect is short lived, levels returning to normal within 2 months of redecoration ending. There is evidence of a seasonal trend for dust loading and lead loading but not for lead concentration. The implications of these findings for blood lead — dust lead exposure studies are considered.