A two-year longitudinal reference range study for selected serum enzymes in a population more than 60 years of age.

The reference ranges for alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatine kinase (CK) in a population greater than 60 years were studied using commercially available reagents. All ranges except those for AST and ALT in women were higher than the ranges found in 20-50-year-old adults. A two-year longitudinal study indicated that individuals who had values above those found in younger adults did not show a greater incidence of disease than did individuals who had values in the lower portion of the distribution curve. Comparison of enzyme values at the beginning and at the end of the two-year study showed that mean ALP, AST, ALT, and LDH values (except for ALT values in men) increased gradually. It was concluded from these two findings that the higher values observed for the aging population were a result of the normal aging process, and thus these values were included in the reference range for this population. The range for CK in individuals greater than 60 years was also higher than that found for younger adults, but the mean value of the group was lower, except in women aged 60-69 years, in whom the mean value showed a slight increase over that found for normal adult women. This was believed to be the result of two independent processes; an increase in enzyme activity due to aging and a decrease in enzyme activity due to reduction in muscle mass as a result of the decreased muscular activity of some volunteers during retirement.