Functional capacity, renal function and vitamin D in community-dwelling oldest old

The aim of this study was to evaluate the association between the decline in estimated glomerular filtration rate (eGFR) and serum 25(OH)D with the physical and mental functional capacity of elderly individuals aged 80 years or older.

We evaluated the functional capacity in its multidomain aspects: Geriatric Depression Scale (GDS), Instrumental Activities of Daily Living (IADL), Mental State Mini-Exam (MMSE), Verbal Fluency Test (VF), handgrip strength and time to sit and rise from a chair five times, combined creatinine and cystatin C-based eGFR and 25(OH)D levels in 205 independent asymptomatic and community-dwelling elderly subjects in a cross-sectional study.

Every 1 year of life, there was reduction of about 10% chance of adequate performance in functional capacity. Each 1 ml/min/m² in eGFR was associated with 2% better chance of adequate performance in the IADL. We found no association between eGFR and cognition. Serum 25(OH)D between 15.00 and 22.29 ng/ml increased the chance of better performance in VF, IADL, handgrip strength and sit and rise from the chair compared to the lower level of serum vitamin D.

Decreased renal function associated with age compromises the ability to perform activities for independent life in the community, but we did not observe influence in specific domains of cognition and physical performance. Low serum level of 25(OH)D appears to be a marker of greater risk of functional decline than eGFR measurement in independent oldest old dwelling in the community.