Distressing Dreams in Middle Age May Predict Cognitive Decline, Dementia Risk

In middle-aged and older adults without cognitive impairment or Parkinson disease (PD), distressing dreams may be predictive of cognitive decline and all-cause dementia, particularly in men. These are the findings of a prospective, longitudinal analysis of 3 population-based cohorts published in the journal eClinicalMedicine.

Distressing dreams are linked to more rapid cognitive decline and increased risk for dementia in individuals with PD. For the study, researchers evaluated the association between self-reported distressing dream frequency and risk for cognitive decline and incident dementia among community-dwelling men and women without cognitive impairment or PD.

The middle-aged patient cohort in the present analysis included individuals from the Midlife in the United States (MIDUS) study, which was initiated in 1995. For the current study, baseline was defined as MIDUS Wave 2 (January 2004 to September 2009), in which 1016 adults participated in both the Biomarker Subproject (during which time the Pittsburgh Sleep Quality Index [PSQI] was administered) and the Cognitive Subproject (during which detailed cognitive evaluations were initially administered).

Among the 1016 adults who participated in both subprojects, only those who were middle-aged (ie, 35-64 years) at baseline, completed the questionnaire item on distressing dreams (99.9%), and had baseline cognitive function data available were included in the current analysis (n=745). Following certain study exclusions, a total of 605 men and women remained in the middle-aged cohort.

The mean patient age in this middle-aged cohort was 50 years (range, 44-57 years). Cognitive decline in this cohort was defined as having an annual rate of decline in cognitive function of ≥1 standard deviation faster than the mean decline rate from baseline to follow-up.

The older women in the current analysis were from the Study of Osteoporotic Fractures (SOF) — an observational, longitudinal cohort study where researchers enrolled a total of 10,366 community-dwelling women aged 65 years and older at 4 clinical centers in the United States — Baltimore, Minneapolis, Portland, and Pittsburgh. In the current analysis, baseline for SOF participants was defined as Visit 8 (January 2002 to April 2004), during which the Pittsburgh Sleep Quality Index (PSQI) was administered. Among the 4621 women who participated in Visit 8, only those who completed the questionnaire on distressing dreams (95.7%) and had data available to determine baseline cognitive status were included in the analysis (n=3151). Following certain exclusions, a total of 1475 women remained in the pooled older adult cohort.

The older men in the current analysis were from the Osteoporotic Fractures in Men Study (MrOS) — an observational, longitudinal cohort study where researchers enrolled 5994 community-dwelling men aged 65 years and older at 6 clinical centers in the United States — Birmingham, Minneapolis, Palo Alto, Pittsburgh, Portland, and San Diego. In this analysis, baseline for MrOS participants was defined as either Sleep Visit 1 (December 2003 to March 2005) or Sleep Visit 2 (November 2009 to March 2012), during which the PSQI was administered. Following certain exclusions, a total of 1125 men remained in the pooled older adult cohort.

The risk for incident all-cause dementia was investigated in a total of 2600 older adults (1475 women and 1125 men) pooled from the SOF and MrOS studies. The mean participant age among the older adults was 83 years (range, 81-84 years). All individuals were dementia-free at baseline and were followed up for a maximum of
7 years (range, 4-5 years). Incident dementia was based on physician diagnosis.

In all cohorts, the frequency of distressing dreams was evaluated using item 5h of the PSQI. Multivariable analysis was used to assess the association between self-reported distressing dream frequency (ie, “never,” “less than weekly,” or “weekly”) and later cognitive outcomes in both middle-aged and pooled older adult cohorts. Following adjustments for all covariates, a higher frequency of distressing dreams was linearly statistically significantly associated with a higher risk for cognitive decline among middle-aged adults (P for trend =.016) and a higher risk for incident all-cause dementia among older adults (P for trend <.001).

Compared with middle-aged adults who reported experiencing no distressing dreams at baseline, those who reported experiencing weekly distressing dreams had a 4-fold risk for experiencing cognitive decline (adjusted odds ratio [aOR], 3.99; 95% CI, 1.07-14.85; P =.039). Among older adults, the difference in risk for dementia was 2.2-fold (aOR, 2.21; 95% CI, 1.35-3.62; P =.002).

Per sex-stratified analyses, the associations between distressing dreams and both of the cognitive outcomes — that is, cognitive decline and risk for dementia — were statistically significant among men only.

The study does include several limitations. As with most large population-based cohorts, no clinical dementia adjudication or information on subtypes of dementia was available. Further, the questionnaire item used to evaluate distressing dreams does not clearly differentiate between bad dreams (ie, distressing dreams without awakenings) and nightmares (ie, distressing dreams with awakenings). Thus, it is not possible to establish whether the associations with later cognitive outcomes may vary according to distressing dream subtype.

The researchers concluded that “These findings may help to identify individuals at risk of dementia and could facilitate early prevention strategies.”

Disclosure: The study author has declared no affiliations with biotech, pharmaceutical, and/or device companies.