Neuroticism is recognized as the personality domain that is most strongly associated with behavioral and psychological symptoms (BPS) of Alzheimer's disease (AD). Two sub-components of neuroticism have been recently isolated. Neuroticism-withdrawal (N-withdrawal) refers to the tendency to internalize negative emotion, whereas neuroticism-volatility (N-volatility) reflect the predisposition to externalize negative emotions.
The objective of the current study was to investigate the specific influence of these two sub-components of neuroticism on BPS.
One hundred eighty-seven patients with prodromal or mild AD were drawn from the PACO study (Personalité Alzheimer COmportement). Neuroticism and its facets were assessed at baseline using the NEO-PI-R inventory. N-withdrawal and N-volatility were isolated using a principal component analysis led on the six facets composing neuroticism. BPS were measured with the short version of Neuropsychiatric Inventory (NPI-Q) and collected at baseline, then every 6 months over an 18-month follow-up. Linear mixed-effect analyses were conducted to investigate the association between N-withdrawal, N-volatility, and the severity of BPS over the follow-up.
Mean age of the participant was 79.2±6.5; 59% were female; mean MMSE was 24.5±2.5. Both N-volatility and N-withdrawal were related with the NPI-Q (p < 0.001; p = 0,004). N-withdrawal was positively associated with anxiety (p = 0.001) and depression (p = 0.002), while N-volatility was positively related to delusions (p = 0.004), agitation/aggression (p < 0.001), irritability/volatility (p = 0.037), and apathy (p = 0.021).
The present study demonstrates that N-volatility and N-withdrawal influence the risk of developing BPS in a different way. These results highlight the relevance of considering sub-components of neuroticism when studying links between personality and BPS.