During the past few decades age at death for individuals with Down syndrome (DS) has increased dramatically. The birth frequency of infants with DS has long been constant in Sweden. Thus, the prevalence of DS in the population is increasing. The aim of the present study was to analyze mortality and causes of death in individuals with DS during the period 1969-2003. All individuals with DS that died between 1969 and 2003 in Sweden, and all individuals born with DS in Sweden between 1974 and 2003 were included. Data were obtained from the Swedish Medical Birth Register, the Swedish Birth Defects Register, and the National Cause of Death Register. Median age at death has increased by 1.8 years per year. The main cause of death was pneumonia. Death from congenital heart defects decreased. Death from atherosclerosis was rare but more frequent than reported previously. Dementia was not reported in any subjects with DS before 40 years of age, but was a main or contributing cause of death in 30% of the older subjects. Except for childhood leukemia, cancer as a cause of death was rare in all age groups. Mortality in DS, particularly infant mortality, has decreased markedly during the past decades. Median age at death is increasing and is now almost 60 years. Death from cancer is rare in DS, but death from dementia is common.

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Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant polyglutamine disorder presenting with progressive cerebellar ataxia and blindness. The molecular mechanisms underlying the selective neuronal death typical of SCA7 are unknown. We have established SCA7 cell culture models in HEK293 and SH-SY5Y cells, in order to analyse the effects of overexpression of the mutant ataxin-7 protein. The cells readily formed anti-ataxin-7 positive, fibrillar inclusions and small, nuclear electron dense structures. We have compared the inclusions in cells expressing mutant ataxin-7 and in human SCA7 brain tissue. There were consistent signs of ongoing abnormal protein folding, including the recruitment of heat-shock proteins and proteasome subunits. Occasionally, sequestered transcription factors were found. Activated caspase-3 was recruited into the inclusions in both the cell models and human SCA7 brain and its expression was upregulated in cortical neurones, suggesting that it may play a role in the disease process. Finally, on the ultrastructural level, there were signs of autophagy and nuclear indentations, indicative of a major stress response in cells expressing mutant ataxin-7.

Spinocerebellar ataxia 7 (SCA7) is a neurodegenerative disease caused by the expansion of a CAG repeat encoding a polyglutamine tract in the protein ataxin-7. We developed antibodies directed against two different parts of the ataxin-7 protein and studied its distribution in brain and peripheral tissue from healthy subjects. Normal ataxin-7 was widely expressed in brain, retina and peripheral tissues, including striated muscle, testis and thyroid gland. In the brain, expression of ataxin-7 was not limited to areas in which neurones degenerate, and the level of expression was not related to the severity of neuronal loss. Immunoreactivity was low in some vulnerable populations of neurones, such as Purkinje cells. In neurones, ataxin-7 was found in the cell bodies and in processes. Nuclear labelling was also observed in some neurones, but was not related to the distribution of intranuclear inclusions observed in an SCA7 patient. In this patient, the proportion of neurones with nuclear labelling was higher, on average, in regions with neuronal loss. Double immunolabelling coupled with confocal microscopy showed that ataxin-7 colocalized with BiP, a marker of the endoplasmic reticulum, but not with markers of mitochondria or the trans-Golgi network.