Neuropsychiatric symptoms in mild cognitive impairment: differences by subtype and progression to dementia

Neuropsychiatric symptoms (NPS) are common in patients with mild cognitive impairment (MCI). Little is known, however, about how NPS vary by MCI subtype (i.e. amnestic, single domain non-memory, and multiple domain). In addition, it is unclear whether NPS increase risk of progression to dementia. We investigated the distribution of NPS across MCI subtypes and determined whether NPS increase risk of progression to dementia.

Participants were 521 patients diagnosed with MCI at the Alzheimer's Research Centers of California between 1988 and 1999. At baseline, patients were classified into MCI subtypes and were assessed for NPS.

The mean number of NPS was 2.3 (range 0-9.6; 74% had > or =1 NPS). Patients with > or =4 NPS had more medical comorbidities and greater functional impairment (p < or = 0.0001 for both). Patients with > or =4 NPS were more likely than patients with 0-3 NPS to have amnestic MCI (81% vs 71%, respectively, p = 0.03), and patients with amnestic MCI were more likely than those with other subtypes to exhibit depressive symptoms. Patients with > or =4 NPS had nearly 2.5 times the odds of developing dementia at follow-up than patients with 0-3 NPS (adjusted OR = 2.44, 95% CI 1.07, 5.55).

NPS are common in MCI patients. Those with an elevated number of NPS may be more likely to have the amnestic subtype of MCI, and depression may be more common in amnestic MCI than in other subtypes. An elevated number of NPS may increase risk of progression to dementia for patients with MCI.