The relationship of total serum cortisol to age and lymphocyte subsets.

A) Serum cortisol decreased in an age-dependent manner (n = 34; r = −0.37, P<0.05). B) Both relative (n = 34) and absolute counts (n = 30) of CD8+ decreased with increasing concentration of serum cortisol (r≤−0.34, P<0.05). Relative data not shown. C) A negative correlation was observed between cortisol concentration and absolute CD3+ cell count, although it failed to reach significance (n = 30; r = −0.34, P = 0.068). The black line represents the results of linear regression analysis for each graph.