Subtle neurological abnormalities as risk factors for cognitive and functional decline, cerebrovascular events, and mortality in older community-dwelling adults

Abstract

Background: Subtle, but clinically detectable, neurological abnormalities (SNAs) are associated with impaired physical performance in elderly persons without overt neurological diseases. We investigated whether SNAs were prospectively associated with cognitive and functional status, death, and cerebrovascular events (CVEs) in older community-dwelling individuals.

Methods: In participants without history of stroke, parkinsonism and dementia, or cognitive impairment, a score (N(SNA)) was obtained by summing SNAs detected with a simple neurological examination. Cognitive status and disability were reassessed 4 years later, and deaths and CVEs were documented over 8 years.

Results: Of 506 participants free of neurological diseases (mean [SEM] age, 71.9 [0.3] years; 42% were men), 59% had an N(SNA) of 1 or more (mean [SEM], 1.1 [0.06]; range, 0-8). At baseline, the N(SNA) increased with age and with declining cognitive and physical performance, depressive symptoms, and disability, after adjusting for several covariates, but did not increase with falls and urinary incontinence. The N(SNA) prospectively predicted worsening cognitive status and disability, adjusting for demographics and for baseline comorbidity and cognitive and physical performance. The mortality rates were 22.6, 23.3, 23.9, 58.6, and 91.9 per 1000 person-years in participants with an N(SNA) of 0, 1, 2, 3, and 4 or higher, respectively. Compared with an N(SNA) of less than 3, having an N(SNA) of 3 or higher was associated with an increased adjusted risk of death (hazard ratio, 1.77; 95% confidence interval [CI], 1.25-2.74) and of CVE (hazard ratio, 1.94; 95% CI, 1.07-3.54) over 8 years.

Conclusion: In this sample of older community-dwelling persons without overt neurological diseases, multiple SNAs were associated with cognitive and functional decline and independently predicted mortality and CVEs.

Figure 1

Prediction of functional and cognitive decline from 1995 to 1999 in 420 older community-dwelling persons free of overt neurological diseases at baseline. All analyses adjusted for age, sex, baseline comorbidity, physical performance, cognitive functioning, and basic and instrumental activities of daily living (BADLs and IADLs, respectively). N_SNA indicates the number of subtle neurological abnormalities; the error bars indicate the mean ± SE. A, BADL analysis; B, IADL analysis; C, Mini-Mental State Examination (MMSE) analysis.

Figure 2

Cumulative survival and cumulative event-free survival during the follow-up period. Mortality (A) and incident hospitalization for cerebrovascular events (B) in 506 older community-dwelling persons free of overt neurological diseases, by number of subtle neurological abnormalities (N_SNA) (<3 vs ≥3). Cox proportional hazard models were adjusted for age, sex, baseline comorbidity, cognitive and physical performance, and functional status at baseline (A and B) and history of transient ischemic attacks (B). CI indicates confidence interval; HR, hazard ratio.