Association between higher cerebrospinal fluid levels of phosphorylated tau and reduced depressive symptoms in patients with cognitive decline

Aim In individuals with cognitive decline, depressive symptoms can affect disease progression and quality of life. One factor that may be associated with depressive symptoms is phosphorylated tau (p‐tau). However, the association between p‐tau and depressive symptoms remains controversial. The present study examined the relationship between p‐tau levels and depressive symptoms not only in terms of total scale scores of the 15‐item Geriatric Depression Scale (GDS‐15) but also at the item level. Methods We conducted a cross‐sectional survey of patients ( n = 88) with mild cognitive impairment due to Alzheimer's disease (AD) or with AD dementia (ADD), who were strictly diagnosed by a board of psychiatrists and neurologists from Hokkaido University Hospital. All patients underwent lumbar puncture to obtain cerebrospinal fluid for the p‐tau assessment. We first investigated the association between p‐tau level and GDS‐15 total score. Next, we compared the p‐tau levels for each item using the GDS‐15 with binary responses “none (0)” or “present (1).” Results Multivariable regression analysis revealed that higher levels of p‐tau were significantly associated with lower GDS‐15 total scores (standardized coefficient [95% confidence interval] = −0.28, [−0.48, −0.09]). Furthermore, patients with higher p‐tau levels were less likely to have symptoms of GDS‐15 Items 2 (Dropped interests) ( p < 0.001) and 14 (Hopeless) ( p = 0.0030). Conclusion Our findings suggest an association between p‐tau accumulation and reduced depressive symptoms. However, future longitudinal studies are required to confirm whether p‐tau may be a predictive factor for depressive symptoms.