Hippocampal Volume Changes in Patients with Asthma

BACKGROUND: Prior research suggests a possible association between asthma and decreased hippocampal volumes. OBJECTIVE: This study examines the association between asthma and hippocampal volume. METHODS: We conducted an analysis of participants in the Dallas Heart Study (DHS). The DHS collected an epidemiological sample of Dallas County residents to explore risk factors for heart disease. Included were 1,287 adults with complete data on study variables and without history of stroke, emphysema, or more than 5 drinks per day. Study variables included gender, age, race, and education as demographic characteristics, cognitive ability measured by the Montreal Cognitive Assessment (MoCA), and brain segment volumes measured by FreeSurfer. Study outcome variables were total, right, and left hippocampal volumes measured using FreeSurfer. General Linear Models (GLM) were conducted to examine the association of asthma diagnosis with hippocampal volumes after controlling for demographic characteristics, total MoCA score, and brain segment volume. Analysis of Variance (ANOVA) was used to examine the effect of gender on hippocampal volumes. RESULTS: The prevalence of lifetime asthma diagnosis among our study samples was 10.8% with 9.6% in males and 11.7% in females. Our study participants with a self-reported asthma diagnosis had significantly smaller estimated total, right, and left hippocampal volumes (95% CI 0.13%-2.9%; p = 0.03) than those without an asthma diagnosis. Asthma was significantly associated with total, right, and left hippocampal volumes in males, while not significantly associated in females after controlling for demographic characteristics, total MoCA score, and brain segment volume. Total, right, and left hippocampal volumes of males with asthma diagnoses, respectively, were 3.0% smaller (95% CI 0.77%-5.2%; p = 0.008), 2.9% smaller (95% CI 0.58%-5.2%; p = 0.014), and 3.1% smaller (95% CI 0.70%-5.6%; p =0.012) than males without asthma. CONCLUSION: Hippocampal volume in a large and diverse sample of adults was significantly smaller in people with asthma as compared to those without asthma. This difference in volume was limited to males. These findings suggest that asthma may be associated with structural brain differences as well as respiratory effects. Because the hippocampus is a brain region involved in memory formation these findings may have implications for treatment adherence.