History of infections is associated with smaller hippocampal volume in older women

Abstract

AbstractBackgroundAccumulating evidence suggests that infections can play a major role in Alzheimer’s disease (AD), however, mechanism is unclear as multiple pathways may be involved. One possibility is that infections might contribute to AD directly by promoting neuronal death and neurodegeneration.MethodWe investigated the relationship between history of infectious diseases (a potential AD risk factor) and brain hippocampal volume, HV (a biomarker of neurodegeneration and AD neuropathology) in a subsample of the UK Biobank participants with respective information. Infectious disease diagnoses were based on ICD‐10 codes. The left/right HV was measured by the MRI. Analysis of variance (ANOVA) and Welch Two Sample t‐test were used to examine the statistical significance.ResultThe HV was significantly lower in older women (age 65+) with prior history of infections, compared to the same age women without such history (p‐value = 0.014 and 0.029, for the left and right HV, respectively). The effect size increased with age, and this increase was faster for the right vs. left HV. The difference in HV between male subjects with and without history of infections was not statistically significant.ConclusionIn this study, prior infections were significantly associated with the lower left/right HV in women aged 65+, which supports the role of infectious diseases in neurodegeneration and preclinical AD pathology in females. The effect size increased with age, in line with the increase in brain vulnerability to stressors due to aging. The faster increase for the right vs. left HV might indicate that females’ verbal memory declines faster with age compared to visual‐spatial memory, following the exposure to infectious disease, which deserves further investigation. The observed sex differences may reflect a higher vulnerability of the female brain to infection‐related factors, which in turn might contribute to the higher risk of AD in women compared to men.