Objective To determine whether a hospital contact for a head injury increases the risk of subsequently developing Parkinson’s disease.Design Population based case-control study.Setting Denmark.Participants 13 695 patients with a primary diagnosis of Parkinson’s disease in the Danish national hospital register during 1986-2006, each matched on age and sex to five population controls selected at random from inhabitants in Denmark alive at the date of the patient’s diagnosis (n=68 445).Main outcome measures Hospital contacts for head injuries ascertained from hospital register; frequency of history of head injury.Results An overall 50% increase in prevalence of hospital contacts for head injury was seen before the first registration of Parkinson’s disease in this population (odds ratio 1.5, 95% confidence interval 1.4 to 1.7). The observed association was, however, due almost entirely to injuries that occurred during the three months before the first record of Parkinson’s disease (odds ratio 8.0, 5.6 to 11.6), and no association was found between the two events when they occurred 10 or more years apart (1.1, 0.9 to 1.3).Conclusions The steeply increased frequency of hospital contacts for a head injury during the months preceding the date at which Parkinson’s disease was first recorded is a consequence of the evolving movement disorder rather than its cause.

Background. The incidence of prostate cancer (PC) has increased during the last 15 years in Denmark, whereas the mortality has remained largely unchanged. This register study aimed to investigate the trends in PC incidence and mortality in Denmark 1978Denmark -2009 (1978 -2007) and a two-year calendar period (2008 -2009). Trends in incidence rates were estimated for specifi c age groups, birth cohorts, and clinical stage. Results. The age-standardised incidence rate of PC increased from 29.2 per 100 000 person-years in 1978 -1982 to 76.2 per 100 000 person-years in 2008 -2009. The incidence increase began primarily in the mid-1990s. The corresponding mortality rates of PC remained largely unchanged during the entire study period; around 19 per 100 000 person-years. The incidence increase was most pronounced among men aged 60 ϩ years. A clear pattern was also seen for selected birth cohorts, with increasing incidence rates among the youngest cohorts, and the highest relative increase in age-specifi c incidence rates was seen among men born between 1943 and 1947. The distribution of stage changed from 1998, with an increasing proportion of PC patients with localised disease. Conclusion. The observed increase in PC incidence during the period 1993 -2009 in Denmark may be attributed primarily to increasing unsystematic use of prostate specifi c antigen (PSA) testing. The mortality rates remained stable during the same period suggesting that there is not yet any major infl uence of intensifi ed PSA screening and more frequent use of curatively intended therapy on the overall prognosis of PC.

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We observed a relative risk of 1.40 (95% confidence interval; 0.86 -2.16) for cancers diagnosed under the age 20 in 6192 offspring of 3431 mothers with a molar pregnancy, indicating it is not a major determinant of childhood cancer. The few established causes of childhood cancer, including various chromosomal anomalies, account for only a small proportion of the total (Little, 1999). There is, however, evidence that certain types of childhood cancer originate in utero, although the underlying biological mechanisms are unclear (Hjalgrim et al, 2002). Maternal characteristics and pregnancy-related events have therefore been the focus of much research (Roman et al, 2005(Roman et al, , 2006. The population-based UK childhood cancer case -control study (UKCCS, 2000), which examined the obstetric records of mothers of 2962 childhood cancer cases aged 0 -14 years and 4864 matched controls found a statistically significant 2.5-fold increased childhood cancer risk among mothers with a previous molar pregnancy (Roman et al, 2005(Roman et al, , 2006, suggesting a common biological process. We therefore conducted a register-based cohort study in Denmark to examine cancer incidence in the offspring of women who had been diagnosed as having a molar pregnancy. MATERIALS AND METHODSWomen who had a molar pregnancy before 2005 were identified using the Danish National Hospital Register, which contains information for virtually all non-psychiatric hospital admissions in Denmark since 1977. Details of children born to these women were obtained from the National Central Population Register (CPR), which was established in 1968 with all citizens having unique personal identification numbers that permit linkage between registers. The follow-up for cancer incidence, determined by linking to the National Danish Cancer Registry which has been in operation since 1943 (Storm et al, 1997), was up to 31 December 2003, the most recent year with complete registration. Although there were no age restrictions for the linkage, we decided to include only cancers diagnosed before the age of 20 years in the analyses.In our analysis, the number of observed cases was compared with those expected. Expected numbers were determined by multiplying the number of person-years of cohort members by the incidence rates of primary cancer in the general population of Denmark (excluding non-melanoma skin cancer), in sex-specific 5-year age groups and 5-year calendar periods of observation. Standardised incidence ratios (SIRs) were calculated by dividing the observed and expected numbers, and exact 95% confidence limits of the SIRs obtained on the assumption of a Poisson's distribution of the observed cancers (Breslow and Day, 1987). Additional analyses involved restricting the age of follow-up to 14 years and to children born after their mother's molar pregnancy, the latter being primarily for comparison with previously published data (Roman et al, 2006). Data were also stratified by sex. RESULTSApproximately 1 million women gave birth between 1977 and 2005 from w...