The association of serum immunoglobulins with cognition and dementia: the Rotterdam Study

Background Chronic inflammation is involved in the pathophysiology of dementia, but the association of serum immunoglobulins with dementia has been understudied and longitudinal data are currently lacking. We investigated the association of serum immunoglobulin (Ig) A, G, and M with cognition and dementia in a population-based cohort. Methods This study was embedded in the Rotterdam Study. Participants with information on serum immunoglobulin levels, measured between 1997 and 2009, were followed for incident dementia until 2016. Assessment of cognitive function and dementia was performed according to validated tests and clinical criteria respectively. We studied the association between serum immunoglobulins with prevalent and incident dementia using logistic regression and Cox proportional hazards regression analyses respectively. We performed linear regression analyses to quantify the cross-sectional association of serum immunoglobulins with global cognition as well as separate cognitive tests. Analyses were adjusted for age, sex, lifestyle, and cardiovascular factors. Results We included 8768 participants (median age of 62.2 years, 57% women, median follow-up 10.7 years). Overall, none of the immunoglobulins was associated with prevalent or incident dementia. Higher IgG levels were associated with lower scores of global cognition (adjusted standardized mean difference - 0.04; 95% confidence interval:- 0.06; - 0.02) and separate cognitive tests. Conclusion In middle-aged and older individuals from the general population, serum Igs were not associated with prevalent or incident dementia, which may imply that serum Igs are not involved in the pathophysiology of dementia. Although higher IgG levels were associated with worse cognitive function, studies with longitudinal data should exclude reverse causation.