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In a population of 302, 000, in a Midlands district of England, the estimated prevalence of idiopathic Parkinson's disease (IPD) increased from 108 to 121 per 100, 000 from 1982 to 1992. Individual general practice prevalence ranged quite widely. Webster ratings were significantly more often scored in 1992, but at a lower level of severity, suggesting earlier diagnosis. Incidence in 1992 was estimated as 12 per 100, 000 per annum. Micrographia, when copying interlocking pentagons, was significantly related to Hoehn & Yahr scores. Over the 10-year period, there has been a considerable change in prescribing: a positive response to medication was confirmed as a good diagnostic indicator. Progression of symptoms and an increase of physical disability was noted in those of the 1982 study alive in 1992.

We conducted a large record-based case-control study testing associations between childhood cancer and natural background radiation. Cases (27,447) born and diagnosed in Great Britain during 1980-2006 and matched cancer-free controls (36,793) were from the National Registry of Childhood Tumours. Radiation exposures were estimated for mother's residence at the child's birth from national databases, using the County District mean for gamma rays, and a predictive map based on domestic measurements grouped by geological boundaries for radon. There was 12% excess relative risk (ERR) (95% CI 3, 22; two-sided P=0.01) of childhood leukaemia per millisievert of cumulative red bone marrow dose from gamma radiation; the analogous association for radon was not significant, ERR 3% (95% CI -4, 11; P=0.35). Associations for other childhood cancers were not significant for either exposure. Excess risk was insensitive to adjustment for measures of socio-economic status. The statistically significant leukaemia risk reported in this reasonably powered study (power ~50%) is consistent with high-dose rate predictions. Substantial bias is unlikely, and we cannot identify mechanisms by which confounding might plausibly account for the association, which we regard as likely to be causal. The study supports the extrapolation of high-dose rate risk models to protracted exposures at natural background exposure levels.

The magnitude of the risks from low doses of radiation is one of the central questions in radiological protection. It is particularly relevant when discussing the justification and optimization of diagnostic medical exposures. Medical X-rays can undoubtedly confer substantial benefits in the healthcare of patients, but not without exposing them to effective doses ranging from a few microsieverts to a few tens of millisieverts. Do we have any evidence that these levels of exposure result in significant health risks to patients? The current consensus held by national and international radiological protection organizations is that, for these comparatively low doses, the most appropriate risk model is one in which the risk of radiation-induced cancer and hereditary disease is assumed to increase linearly with increasing radiation dose, with no threshold (the so-called linear no threshold (LNT) model). However, the LNT hypothesis has been challenged both by those who believe that low doses of radiation are more damaging than the hypothesis predicts and by those who believe that they are less harmful, and possibly even beneficial (often referred to as hormesis). This article reviews the evidence for and against both the LNT hypothesis and hormesis, and explains why the general scientific consensus is currently in favour of the LNT model as the most appropriate dose-response relationship for radiation protection purposes at low doses. Finally, the impact of the LNT model on the assessment of the risks from medical X-rays and how this affects the justification and optimization of such exposures is discussed.

BACKGROUND AND PURPOSE: To test the design and feasibility of a very large randomised controlled trial assessing the efficacy and safety of antithrombotic therapy started within 48 hours of symptom onset in patients with suspected acute ischaemic stroke. DESIGN: Randomised controlled multicentre open study, with a 3 x 2 factorial design, allocating patients to: medium dose subcutaneous heparin (12,500 units twice per day), versus low dose subcutaneous heparin (5000 units twice per day) versus no heparin; and aspirin (300 mg daily) versus no aspirin. Treatment was given for two weeks or until discharge from hospital if sooner. RESULTS: 984 patients were randomised. CT was performed in 924 (94%) (before randomisation in 622/984 (63%). Within 14 days: 97 patients had died (10%), 30 (3.0%) had a fatal or non-fatal recurrent ischaemic stroke, nine (0.9%) had fatal or non-fatal recurrent stroke due to intracranial haemorrhage, and eight (0.8%) had a fatal or non-fatal pulmonary embolus. At six months, vital status was known for 975 patients (99%), of whom 210 (22%) were dead, 373 (38%) were alive but dependent, and 225 (23%) were independent but not fully recovered. CONCLUSIONS: The trial procedures proved practicable and a wide variety of patients were recruited. Sample size calculation based on the event rates confirmed that reliable evidence on the balance of risk and benefit of early antithrombotic therapy might require a study with more than 20,000 patients. Recruitment rates in the pilot study indicated that if about 200 hospitals participated, recruitment could be completed by 1997.