High Serum Aspartate Aminotransferase, Underweight, and Weight Loss in Older People: Results of the KITCHEN-4

Background: Reduced muscle mass is frequently observed in older people and can lead to being underweight and/or weight loss (WL), but prediction and screening systems utilizing hematological biochemical parameters are limited. High serum aspartatSe aminotransferase in conjunction with normal serum alanine aminotransferase (HASNAL) can reflect systemic muscle damage. HASNAL and the incidence of being underweight concomitant with WL (UWWL) were investigated in the present 6-year community-based cohort study. Methods: Clinical parameters, lifestyle, the incidence of being underweight, ≥5% WL, and UWWL were investigated in 238,536 Japanese people aged 40–68 years who had normal serum alanine aminotransferase. HASNAL was defined as serum aspartate aminotransferase ≥30 U/L and serum alanine aminotransferase <30 U/L. The subjects were divided into a younger group (<55 years) and an older group (≥55 years). Results: After 6 years, overall body weight had increased by 0.4% in the younger group and decreased by 0.4% in the older group. In logistic regression analysis, in the younger group ≥5% WL was significantly associated with baseline HASNAL compared to baseline low serum aspartate aminotransferase (<20 U/L). In the older group, baseline HASNAL was significantly associated with being underweight, ≥5% WL, and UWWL, even after adjustment for potential confounders, and UWWL was inversely associated with regular exercise and daily alcohol consumption—both of which modified the aforementioned associations. Conclusions: Older subjects with HASNAL were at an increased risk of UWWL, possibly via skeletal muscle damage, which may be affected by common lifestyles.