Money, Renal Function, and Cognition

There are two manuscripts of note regarding cognitive function and cognitive decline in this week's issue of the journal Neurology. While I have commented previously about various aspects of dementia, cognitive decline and mild cognitive impairment (MCI) are more common and the latter may be a precursor to dementia.

The first is a discussion of the association between renal function and cognitive decline. 886 persons were taken from a large prospective study of older persons in 40 residential facilities in Chicago. None had dementia at the time of enrollment. Mean age at enrollment was 80.6 years old, and average follow up was 3.4 years. A variety of demographic and medical data were obtained, and 19 different cognitive tests were administered. Renal function was divided dichotomously.

The authors found an association between renal impairment and rate of decline, but not baseline cognitive function. The association remained when persons with severely impaired renal function were censored from the cohort, and was also unaffected when controlling for use of a wide variety of medications. The magnitude of the difference is significant: A one standard deviation change in renal function was associated with cognitive decline comparable to a participant being three years older. Also, the comparative cognitive decline was about 75% of the effect size of presence of the apoE4 genotype. That is quite large.

In this study, baseline renal function was related to, in addition to other factors, physical and social activity, and vascular risk factors and diseases. However, there was no association with education, BMI, or depression. Of note: Since physical and social activity, as well as some vascular risk factors, may be modified, it is possible that some of the deleterious effects of renal impairment on cognition may be mitigated.

The other study evaluated management of financial matters as a predictor of progression to dementia. The authors compared changes in financial capacity over a one year study interval. 87 patients with MCI were recruited, and divided into 2 groups as the study progressed: Patients who became demented during the study period (MCI converters, n=25, 28.7% of the sample), and patients with MCI who did not develop dementia (MCI nonconverters, n=62). These were compared to controls (n=76) recruited from the community. Participants were evaluated using the Financial Capacity Instrument (FCI), a neuropsychological test which evaluates financial capacity at 3 levels: "specific financial abilities (tasks), broader financial activities (domains) important to independent functioning, and overall financial capacity (global scores)." To control for baseline financial ability, t he Prior/Premorbid Financial Capacity Form (PFCF) was given to patients and another information source such as a family member. Typical baseline and demographic data were also obtained.

They found that financial abilities predicted future impairment. At baseline, the control group showed statistically significantly superior performance in all FCI domains, and the nonconverter group was superior to the converter group in many areas. Over the one year study period, only patients in the converter group showed significant deterioration, seen on a small number of items. The authors note that worsening checkbook management skills appear to be an early change seen in MCI patients who developed dementia, and this may be a clinically useful indicator in future. They also suggest that patients with MCI be monitored for changes in financial capacity.

The reader is advised to keep a close watch on renal function in older persons, and ask patients with MCI about how they are faring with managing their money and financial matters.