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This week in BMJ Saturday 11 January 1997

Short children are not necessarily at a psychosocial disadvantage

The Wessex growth study compared 106 short normal children with 119 controls of average stature on measures of cognitive development, self concept development, behaviour, and locus of control (p 97). Social class had a significant effect on all measures, with children in the lower classes doing "worst". The effect of height on all measures was much smaller than the effect of social class. Short children displayed slightly lower IQ, less internalisation of control, and less satisfaction with their height but were, however, happier with their general appearance. Any dissatisfaction short children may have with their height does not seem to affect their emotional wellbeing adversely

Environmental contamination with radiation is associated with childhood leukaemia clusters

Despite extensive research the reasons for the increased incidence of childhood leukaemia around nuclear installations, such as Sellafield and Dounreay in Britain, are still largely unknown. La Hague in France is also a nuclear reprocessing plant operating on an industrial scale and offers an independent opportunity to research into this issue. The main finding of a case-control study around La Hague was that the use of local beaches by children and mothers was associated with the development of leukaemia among people aged under 25 years (p 101). Evidence was found of a causal role for environmental radiation exposure, which suggests a totally different pathway to the occupational exposure, putting the environmental hypothesis again in the limelight

When does the fetus become a viable baby?

While the birth of a baby more than 12 weeks early poses many dilemmas, the threshold of viability has certainly been pushed back by the advent of respiratory support. Recent North American guidelines have suggested that survival occurs at 22 weeks, but Win Tin et al for the Northern Neonatal Network found no evidence for this in any white community (p 107) and identified only eight survivors among the 197 babies of 23 weeks' gestation who were alive at the start of labour in their own study (half of whom had severe disability at 2 years). A 6O% increase in survival in babies of under 28 weeks over the 12 years of the study had not been accompanied by any change in the proportion with disability, with 10% never likely to achieve mobility or communicate intelligibly. Recent developments have improved the outlook for the viable baby but have not changed the threshold of viability.

Replacing dietary saturated fat with other fats significantly reduces blood cholesterol

The quantitative importance of diet to blood cholesterol remains uncertain because nonexperimental dietary studies in community subjects are unreliable and experimental ("metabolic ward") studies have been too small to be reliable. Clarke et al (p 112) conducted a meta-analysis of 395 published metabolic ward experiments of the effects of dietary lipids on blood cholesterol. Isocaloric increases in saturated fat intake increased blood total and low density lipoprotein cholesterol and, to a lesser degree, high density lipoprotein cholesterol. Increased polyunsaturated fat intake decreased total and low density lipoprotein cholesterol and increased high density lipoprotein cholesterol, while monounsaturated fat had no significant effect on total and low density lipoprotein cholesterol but increased high density lipoprotein cholesterol. In the average British diet, replacement of 60% of saturated fat by other dietary fats and avoidance of 60% of dietary cholesterol would reduce blood cholesterol by about 0.8 mmol/l.