BackgroundOlder adults married to persons living with dementia (PLwD) may be at risk for loneliness and depression. We assessed the prevalence of loneliness and depressive symptoms among spouses of PLwD or cognitive impairment not dementia (CIND), and the role of marital quality in mediating these outcomes.MethodsWe used a US population‐based sample of 4071 couples enrolled in the Health and Retirement Study (2014 and 2016). We included older adults married to PLwD (N = 227), married to persons with CIND (N = 885), or married to persons with no cognitive impairment (NCI) (N = 2959). We determined the prevalence of loneliness (UCLA 3‐item scale), depressive symptoms (CESD‐8 scale), and both, using multivariable logistic regression adjusting for sociodemographic and health‐related characteristics. We then tested for interaction terms between marital quality (4‐item scale) and degree of spousal cognitive impairment for each outcome of loneliness and depressive symptoms.ResultsThe sample was 55% women and on average 67‐years‐old (range: 50–97). After adjustment, spouses of persons with cognitive impairment were more likely to be lonely (NCI: 20%, CIND: 23%, PLwD: 29%; p = 0.04), depressed (NCI: 8%, CIND: 15%, PLwD: 14%; p < 0.01), and both (NCI: 4%, CIND: 9%, PLwD: 7%; p < 0.01). The association between cognition and loneliness, but not depression, differed by marital quality (interaction p‐value = 0.03). Among couples with high marital quality, spousal cognitive impairment was associated with higher likelihood of loneliness (p < 0.05). In contrast, no association existed between spousal cognition and loneliness among couples with lower marital quality (p = 0.37).ConclusionsOne in six spouses of persons with CIND or more advanced disease (PLwD) experienced depressive symptoms, and loneliness among spouses of PLwD was experienced at a twofold rate. By identifying and managing both, and facilitating interventions that promote high‐quality social connection, clinical teams might improve the lives of older couples facing dementia.