Infections and activated immune responses can affect the brain through several pathways that might also affect cognition. However, no large-scale study has previously investigated the effect of infections on the general cognitive ability in the general population.
Danish nationwide registers were linked to establish a cohort of all 161,696 male conscripts during the years 2006-2012 who were tested for cognitive ability, which was based on logical, verbal, numerical and spatial reasoning at a mean age of 19.4 years. Test scores were converted to a mean of 100.00 and with a standard deviation (SD) of 15. Data were analyzed as a cohort study with severe infections requiring hospitalization as exposure using linear regression.
Adjusted effect sizes were calculated with non-exposure to severe infections as reference, ranging from 0.12 SD to 0.63 SD on general cognitive ability. A prior infection was associated with significantly lower cognitive ability by a mean of 1.76 (95%CI: -1.92 to -1.61; corresponding to 0.12 SD). The cognitive ability was affected the most by the temporal proximity of the last infection (P
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Cites: J Neurosci. 2012 Jan 11;32(2):436-5122238080
The ultimate causes of idiopathic Parkinson's disease (PD) are not fully known, but environmental and occupational causes are suspected. Postencephalitic parkinsonism has been linked to influenza, and other viral infections have also been suspected to relate to PD. We estimated the relationship between PD and both infections and possible vectors of infection (i.e., animal and human) in a population-based, case-control study in British Columbia, Canada. We recruited 403 cases detected by their use of antiparkinsonian medications and 405 controls from the registrants of the provincial universal health insurance plan. Severe influenza was associated with PD (odds ratio [OR]: 2.01; 95% confidence interval [CI]: 1.16-3.48), although this effect was attenuated when reports were restricted to those occurring 10 or more years before diagnosis. Childhood illnesses were inversely associated with PD, particularly red measles (OR: 0.65; 95% CI: 0.48-0.90). Several animal exposures were associated with PD, with statistically significant effects for cats (OR: 2.06; 95% CI: 1.09-3.92) and cattle (OR: 2.23; 95% CI: 1.22-4.09). Influenza infection may be associated with PD. The inverse relationships with childhood infections may suggest an increased risk with subclinical or asymptomatic childhood infections. Occupational exposure to animals may increase risk through transmission of infections or may indicate exposure to another agent of interest (e.g., bacterial endotoxin).
Sixty-four young adults (aged 16 to 40 years) with ischemic stroke were analyzed in retrospect with regard to possible pathogenetic mechanisms. In older patients various predisposing factors emerge (arterial hypertension, hyperlipidemia etc.) which are rare among younger age groups. In patients lacking predisposing causes the stroke incidence exhibits a seasonal variation. It is suggested that infection may be important for the development of ischemic stroke.
Greenland is a high-incidence area for certain virus-associated cancers. The long term cancer risk in a cohort of 7,761 Danish employees who had been working for some time (median 19.7 months) in Greenland during the period 1955-1978 was studied. During a total of 162,300 person-years (average 20.9 years) of follow-up ending on December 31, 1992, the number of cancers observed was 732 vs. 669 expected (relative risk (RR) = 1.09, 95% confidence interval (CI) 1.02-1.18). Whereas the men did not experience any unusual cancer incidence at any cancer site, the women were at elevated risk of developing breast cancer (RR = 1.5, 95% CI 1.2-1.8 (n = 96)); malignant melanoma (RR = 1.8, 95% CI 1.0-2.9 (n = 16)); and lymphatic and hematopoietic malignancies (RR = 1.7, 95% CI 1.0-2.8 (n = 16)). Exposure during adulthood to a high-incidence area for cervical cancer, nasopharyngeal carcinoma and tumors of the major salivary glands did not confer any measurable increase in the risk for these virus-associated cancers. Postponement of childbearing might explain part of the elevated breast cancer risk. Intensive exposure to ultraviolet light, that is likely to explain the increased risk of malignant melanoma among the women, might also be involved in the excess incidence of lymphatic and hematopoietic malignancies observed in these women. However, why the men did not experience similar alterations in the risk of melanoma and cancers of the immune system is enigmatic.
A previously healthy woman was admitted to hospital after 'flu-like' symptoms for 5 days followed by acute intense abdominal and lower back pain. On admission she was found to be in severe shock and was transferred to the ICU. Echocardiography revealed cardiac tamponade, and pericardiocentesis was performed immediately. Thereafter her cardiovascular state improved, but she developed hypotension with low systemic vascular resistance and required vasoactive treatment for 4 days. Nine days after admission the patient was transferred to the ward, after which she recovered rapidly and completely. The cause of her illness was extensively screened. No underlying disease was found, and all bacterial cultures remained negative. Acute virus infection was confirmed by diagnostic elevations of antibody titers to Influenza A and adenovirus. Adenovirus was also isolated from her bronchoalveolar lavage fluid.
Multiple sclerosis has been hypothesized to be the result from an aberrant immune response possibly triggered by delayed exposure to a common childhood infection. Because the vast majority of previous studies testing this hypothesis have been based on a history of childhood infections recalled years to decades later in adulthood, we investigated whether age at six common childhood infections was associated with risk of multiple sclerosis, using information recalled in the childhood of a historical cohort of school children in Denmark. Cases included all individuals with multiple sclerosis in the country born between 1940 and 1975, who had attended school in the capital, Copenhagen. Controls were age- and sex-matched peers. School health records were obtained for all subjects. The records contained information on measles, pertussis, scarlet fever, birth order, sibship size, social class of the father, school years, and name of school and attended school classes for children born since 1940 (n(cases) = 455, n(controls) = 1801). For children born since 1950, the records also contained information on rubella, varicella and mumps (n(cases) = 182, n(controls) = 690). Neither age at infection with measles, rubella, varicella, mumps, pertussis and scarlet fever (upper age limit, 14 years) nor the cumulative number of these infections between the ages of 10 and 14 years was associated with the risk of multiple sclerosis. In addition, the risk of multiple sclerosis was not associated with birth order or social class. No clustering of multiple sclerosis in school classes was observed. Our findings suggest that measles, rubella, mumps, varicella, pertussis and scarlet fever, even if acquired late in childhood, are not associated with increased risk of multiple sclerosis later in life.
