Date Published: May 1, 2018
Publisher: Elsevier, Inc
Author(s): Alex Tsui, Diana Kuh, Marcus Richards, Daniel Davis.
Few population studies have investigated whether longitudinal decline after delirium in mid-to-late life might affect specific cognitive domains.
Participants from a birth cohort completing assessments of search speed, verbal memory, and the Addenbrooke’s Cognitive Examination at age 69 were asked about delirium symptoms between ages 60 and 69 years. Linear regression models estimated associations between delirium symptoms and cognitive outcomes.
Period prevalence of delirium between 60 and 69 years was 4% (95% confidence interval 3.2%–4.9%). Self-reported symptoms of delirium over the seventh decade were associated with worse scores in the Addenbrooke’s Cognitive Examination (−1.7 points; 95% confidence interval −3.2, −0.1; P = .04). In association with delirium symptoms, verbal memory scores were initially lower, with subsequent decline in search speed by the age of 69 years. These effects were independent of other Alzheimer’s risk factors.
Delirium symptoms may be common even at relatively younger ages, and their presence may herald cognitive decline, particularly in search speed, over this time period.
Delirium is a neuropsychiatric syndrome characterized by acute cognitive dysfunction and attentional deficits precipitated by acute illness. Delirium is common, affecting around 25% of older inpatients , , and is associated with increased length of hospital admission, risk of institutionalization, and mortality . In a range of settings, delirium has been linked with subsequent cognitive decline and incident dementia , , , . The precise mechanisms underlying these relationships are unknown but may be independent of classical Alzheimer’s pathologies such as amyloid beta, hyperphosphorylated tau, or APOE ε4 genotype , , .
The MRC National Survey for Health and Development (NSHD) is a British birth cohort study, following a sample of 5362 participants born in March 1946. In 2015, when participants were aged 69 years, 2698 individuals living in England, Scotland, and Wales were invited to have a home visit by a research nurse as part of the 24th follow-up . The other 2664 participants had either died (n = 995), permanently refused participation (n = 654), moved abroad (n = 583), or were lost and untraced (n = 432). Of the 2698 invited, 2148 (80%) completed a home visit and the maximum sample for this analysis is 2090 who responded to a question about delirium symptoms (97%).
Of 2090 participants responding to the delirium question, 83 reported symptoms between ages 60 and 69 years, thus a ten-period period prevalence of 4.0% (95% confidence interval [CI] 3.2%–4.9%). No sex differences were observed (P = .59). Complete ACE-III data were available for 1729 participants (81% of home visits). Participant characteristics for maximum samples by reported delirium symptoms are shown in Table 1.Table 1Patient characteristics of study participants with and without symptoms of delirium between ages 60 and 69 yearsPatient characteristicsnDelirium symptomsNo delirium symptomsP valueVisual search speed (letters, SD) Age 692053237 (76)263 (74)<.01 Age 531968280 (76)284 (73).67Verbal memory (words, SD) Age 69201821 (6)22 (6).14 Age 53195523 (7)25 (6).04Hypertension at age 60–64187522%37%.28Diabetes by 60–64195615%11%.27Smoking status at 60–641808.63 Current13%10% Ex59%57% Never28%33%Level of activity age at 60–641923.39 Inactive66%58% Less active (1–4/week)11%13% More active (>5/week)23%29%Educational attainment by 262090.63