Association Between Estimated Net Endogenous Acid Production and Subsequent Decline in Muscle Mass Over Four Years in Ambulatory Older Chinese People in Hong Kong: A Prospective Cohort Study

Background. Findings regarding dietary acid-base balance and muscle loss were mainly reported in Caucasian populations and seldom documented in Chinese population with different dietary habits. This prospective study examined such association in 3,122 Chinese community-dwelling older people aged 65 and over in Hong Kong. Methods. Baseline dietary intakes were assessed using a validated food frequency questionnaire. Estimated net endogenous acid production (NEAP) was calculated using Frassetto's method based on the diet's protein to potassium ratio. Nutrient intakes and estimated NEAP were energy-adjusted by residual method. Estimated NEAP was divided into sex-specific energy-adjusted quartiles for data analysis. Four-year change in appendicular skeletal muscle mass (ASM) from baseline was assessed using dual-energy X-ray absorptiometry. Analysis of covariance was used to investigate the association between quartiles of estimated NEAP and 4-year change in ASM with adjustments for potential covariates. Results. Median estimated NEAP of the participants was 47.3 (IQR: 35.5, 61) mEq/d. Participants in the highest sex-specific quartile of energy-adjusted estimated NEAP lost significantly more ASM over 4-year than those in the lowest sex-specific quartile of energy-adjusted estimated NEAP in both crude and adjusted models (adjusted mean +/- SE: 0.486 +/- 0.054 vs 0.384 +/- 0.055 kg, p(trend)=.026). Change in gait speed was not associated with the estimated NEAP. Conclusions. Our findings provide evidence of a slower decline in muscle mass in older adults with a lower dietary acid load. More prospective cohort studies in populations with different dietary habits and randomized controlled trials are warranted to examine the role of dietary acid-base balance in age-related decline in muscle loss.