The Incidence of Nonaffective, Nonorganic Psychotic Disorders in Older People: A Population-based Cohort Study of 3 Million People in Sweden.

BACKGROUND

There are limited data on the epidemiology of very late-onset schizophrenia-like psychosis (VLOSLP) and how this relates to potential risk factors including migration, sensory impairment, traumatic life events, and social isolation.

METHODS

We followed up a cohort of 3 007 378 people living in Sweden, born 1920-1949, from their 60th birthday (earliest: January 15, 1980) until December 30 2011, emigration, death, or first recorded diagnosis of nonaffective psychosis. We examined VLOSLP incidence by age, sex, region of origin, income, partner or child death, birth period, and sensory impairments.

RESULTS

We identified 14 977 cases and an overall incidence of 37.7 per 100 000 person-years at-risk (95% CI = 37.1-38.3), with evidence that rates increased more sharply with age for women (likelihood ratio test: χ2(6) = 31.56, P < .001). After adjustment for confounders, rates of VLOSLP were higher among migrants from Africa (hazard ratio [HR] = 2.0, 95% CI = 1.4-2.7), North America (HR = 1.4, 95% CI = 1.0-1.9, P = .04), Europe (HR = 1.3, 95% CI = 1.2-1.4), Russian-Baltic regions (HR = 1.6, 95% CI = 1.4-1.9), and Finland (HR = 1.6, 95% CI = 1.5-1.7). VLOSLP risk was highest for those in the lowest income quartile (HR = 3.1, 95% CI = 2.9-3.3). Rates were raised in those whose partner died 2 years before cohort exit (HR = 1.1, 95% CI = 1.0-1.3, P = .02) or whose child died in infancy (HR = 1.2, 95% CI = 1.0-1.4, P = .05), those without a partner (HR = 1.9, 95% CI = 1.8-1.9) or children (HR = 2.4, 95% CI = 2.3-2.5), and those whose child had a psychotic disorder (HR = 2.4, 95% CI = 2.2-2.6).

INTERPRETATION

We identified a substantial burden of psychosis incidence in old age, with a higher preponderance in women and most migrant groups. Life course exposure to environmental factors including markers of deprivation, isolation, and adversity were associated with VLOSLP risk.