Declining executive control in normal aging predicts change in functional status: the Freedom House Study.

OBJECTIVES

To assess the contribution of executive control function (ECF) to functional status.

DESIGN

Three-year longitudinal cohort study.

SETTING

A comprehensive-care retirement community.

PARTICIPANTS

Five hundred forty-seven noninstitutionalized septuagenarians.

MEASUREMENTS

The Mini-Mental State Examination (MMSE) and Executive Interview (EXIT25). Functional status was assessed using instrumental activities of daily living (IADLs). Latent growth curves of MMSE, EXIT25, and IADL were modeled. The rate of change in IADLs (DeltaIADL), adjusted for baseline IADLs and cognition, was regressed on the rate of change in each cognitive measure (adjusted for baseline cognition). Models were also adjusted for baseline age, level of care, and comorbid illnesses.

RESULTS

Baseline test scores were within normal ranges, but mean EXIT25 scores reached the impaired range by the second follow-up. There was significant variability around the baseline means and slopes for all variables. The rate of change in EXIT25 was strongly correlated with DeltaIADL (r=-0.57, P<.001). This remained significant after adjusting for baseline EXIT25 scores, IADLs, age, comorbid disease, and level of care. The effect of the EXIT25 on DeltaIADL was stronger than those of age, baseline IADLs, comorbid disease, or level of care. The rate of change in MMSE scores was not significantly associated with DeltaIADL.

CONCLUSION

ECF is a significant and independent correlate of functional status in normal aging. Traditional dementia case finding is likely to underestimate cognition-related disability. Neither a normal baseline MMSE score nor stable MMSE scores over time preclude functionally significant changes in ECF.