Frailty and Cognitive Function in Incident Hemodialysis Patients

Abstract

Background and objectives: Patients of all ages undergoing hemodialysis (HD) have a high prevalence of cognitive impairment and worse cognitive function than healthy controls, and those with dementia are at high risk of death. Frailty has been associated with poor cognitive function in older adults without kidney disease. We hypothesized that frailty might also be associated with poor cognitive function in adults of all ages undergoing HD.

Design, setting, participants, & measurements: At HD initiation, 324 adults enrolled (November 2008 to July 2012) in a longitudinal cohort study (Predictors of Arrhythmic and Cardiovascular Risk in ESRD) were classified into three groups (frail, intermediately frail, and nonfrail) based on the Fried frailty phenotype. Global cognitive function (3MS) and speed/attention (Trail Making Tests A and B [TMTA and TMTB, respectively]) were assessed at cohort entry and 1-year follow-up. Associations between frailty and cognitive function (at cohort entry and 1-year follow-up) were evaluated in adjusted (for sex, age, race, body mass index, education, depression and comorbidity at baseline) linear (3MS, TMTA) and Tobit (TMTB) regression models.

Results: At cohort entry, the mean age was 54.8 years (SD 13.3), 56.5% were men, and 72.8% were black. The prevalence of frailty and intermediate frailty were 34.0% and 37.7%, respectively. The mean 3MS was 89.8 (SD 7.6), TMTA was 55.4 (SD 29), and TMTB was 161 (SD 83). Frailty was independently associated with lower cognitive function at cohort entry for all three measures (3MS: -2.4 points; 95% confidence interval [95% CI], -4.2 to -0.5; P=0.01; TMTA: 12.1 seconds; 95% CI, 4.7 to 19.4; P<0.001; and TMTB: 33.2 seconds; 95% CI, 9.9 to 56.4; P=0.01; all tests for trend, P<0.001) and with worse 3MS at 1-year follow-up (-2.8 points; 95% CI, -5.4 to -0.2; P=0.03).

Conclusions: In adult incident HD patients, frailty is associated with worse cognitive function, particularly global cognitive function (3MS).

Keywords: ESRD; african american; black; cognition; dementia; depression; epidemiology and outcomes; frailty; hemodialysis; kidney failure, chronic; renal dialysis.

Figure 1.

Distribution of the Fried Frailty Score in adults initiating hemodialysis. The distribution of the Fried Frailty Score is presented as a histogram of the percentage of participants with a given score. The Fried Frailty Score ranges from 0 to 5, with a higher score representing worse frailty.

Figure 2.

Distribution of baseline cognitive function scores, by frailty status in adults initiating hemodialysis. The distribution of the cognitive function scores at baseline is presented as a boxplot. The median (center bar), 25th percentile (bottom of the box), and 75th percentile (top of the box) are plotted by frailty status. Outliers (data points that fall outside the lower quartile −1.5 × IQR, upper quartile +1.5 × IQR) are noted as dots. (A) Modified Mini-Mental State (3MS) test. (B) Trail Making Test A (TMTA). (C) Trail Making Test B (TMTB). IQR, interquartile range.

Figure 3.

Overlap of frailty, comorbidity, and cognitive impairment in adults initiating hemodialysis. The overlap of frailty, comorbidity, and cognitive function is displayed through a Venn diagram. The percentages represent the proportion of the total population with only cognitive impairment, comorbidity, and frailty as well as the overlap of these three factors. Frailty is defined as ≥3 components as defined by Fried. Comorbidity is defined as ≥4 conditions as specified in the Materials and Methods. Cognitive impairment was defined as a Modified Mini-Mental State (3MS) score <80. The total represents 323 study participants on hemodialysis. The size of each subgroup is indicated in parentheses.