Inflammation From Infection Linked to Increased Risk of Dementia

Inflammation has long been associated with increased risk of Alzheimer’s disease and other types of dementia. Now a study in JAMA Network Open suggests that the increased risk may be tied specifically to inflammation from infection more than general systemic inflammation such as that caused by autoimmune disorders.

Janet Janbek, Ph.D., of Copenhagen University Hospital–Rigshospitalet and colleagues examined data amassed between 1978 and 2018 from nearly 1.5 million adults in Danish national population registries. The individuals were born from 1928 to 1953, were alive and living in Denmark on January 1, 1978, and were included in the study upon their 65th birthday. None of the individuals had a record of diagnosed dementia upon enrollment.

The researchers defined exposure as inpatient, outpatient, or emergency hospital contacts with a primary or secondary discharge diagnosis of an infection or autoimmune disease beginning at age 50.

During the study period, 45% of the individuals had infections and 9% had autoimmune diseases. Five percent developed dementia after age 65.

The researchers found that over the study period, dementia occurred about 1.5 times as often in people who had infections than in people without infections. Furthermore, the more infections people had, the higher the rate of dementia. In contrast, dementia occurred in people who had autoimmune diseases at about the same rate (1.04 times) as people without autoimmune diseases; being diagnosed with multiple autoimmune diseases did not appear to increase the rate of dementia.

“Our data and the observational nature of our study do not directly support or refute any proposed mechanism, nor can we make firm conclusions about the role of inflammation in dementia on the basis of our findings,” the researchers wrote. However, the findings “may point toward a role for infection-specific processes rather than general systemic inflammation.”

For related information, see the Psychiatric News article “History of Severe Infection Linked to Substance-Induced Psychosis.”

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Researchers Uncover Genetic Link to Anorexia

Researchers have uncovered the first genetic variant tied to anorexia nervosa, reports a study published today in AJP in Advance. This large-scale genomic effort also identified many correlations between anorexia and other psychiatric and metabolic disorders, providing a new way to conceptualize this serious and potentially lethal eating disorder.

Past studies of anorexia in twins suggested that the disorder is heritable, but previous genome-wide association studies (GWASs) to uncover risk variants have been limited by small sample sizes.

For the current study, Cynthia Bulik, Ph.D., of the University of North Carolina School of Medicine and an international group of investigators worked together to conduct a GWAS of anorexia, combining samples collected from around the world. The analysis included DNA from 3,495 people with anorexia nervosa and 10,982 controls.

The genome-wide analysis uncovered one variant on chromosome 12 (rs4622308) that was significantly correlated with anorexia nervosa. This locus has been previously shown to be associated with type 1 diabetes and autoimmune disorders.

The researchers next explored the genetic correlations—the extent to which various traits are caused by the same genes—between anorexia and other psychiatric, medical, educational, and personality phenotypes.

Anorexia was significantly genetically correlated with neuroticism and schizophrenia—a relationship the authors noted “reinforce[s] clinical and epidemiological observations.” Other traits with a strong positive association were educational attainment and cholesterol levels. The authors also found strong negative associations between anorexia and obesity, insulin resistance, and fasting insulin levels.

The findings suggest anorexia nervosa is a “complex heritable phenotype with intriguingly large and significant genetic correlations not only with psychiatric disorders but also with multiple metabolic traits,” Bulik and colleagues wrote. “Just as obesity is increasingly considered to be both a metabolic/endocrine and psychiatric disorder, approaching anorexia nervosa as both a psychiatric and metabolic condition could ignite interest in developing or repositioning pharmacological agents for its treatment,” the authors concluded.

For related information, see Handbook of Assessment and Treatment of Eating Disorders from APA Publishing.

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