Longitudinal Total Body Potassium Changes in Healthy Elderly People

Rationale: Age-related diseases and consequent decreased physical activity are main contributors to lean body mass (LBM) loss associated to aging. We hypothesize that total body potassium (TBK), an index of metabolically active LBM, would be decreased in healthy, physically active, elderly volunteers over a 3-year period. Method: LBM was measured by DEXA (Hologic QDR-4500) and TBK by whole body counter at time 0 (T0) and 3 years later (T3). Physical activity (PA) was evaluated by means of a validated frequency questionnaire (1). Statistical analysis between T0 and T3 data were done by means of paired t-test.

Results: 191 volunteers were enrolled. Preliminary data at T0 and T3 for 54 men (72.6±5.4yrs, BMI=25.9±3.0kg/m2) and 53 women (73.2±5.6yrs, BMI=26.9±4.2kg/m2) are shown. All of them, reported engaging in at least 1h of PA/week. No effect of PA on TBK was observed.

	T0	T3
WOMEN Body weight (kg)
LBM (kg)	65.4±11.7	66.2±12.5*
TBK/LBM (mmol/kg)	40.1±4.5	40.0±5.0
MEN Body weight (kg)	57.7±5.3	55.0±5.2*
LBM (kg)	74.2±9.7	74.7±9.5
TBK/LBM (mmol/kg)	53.5±5.6	53.1±5.9*
	60.6±4.9	53.8±8.5**
Mean±SD; T3 vs. T0* P<0.05, ** P<0.001

Conclusions: In healthy and physically active elderly people, LBM is preserved. However, TBK content is reduced, regardless of PA level, suggesting qualitative changes in LBM.

References: 1) Bernstein MS, 1999, Am J Public Health