Methodologically Critical Interactions of Circadian Rhythm, Sex, and Aging Characterize Serum Aldosterone and the Female Adrenopause

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Abstract
Nine 20-to 26-year-old and ten 70-to 78-year-old diurnally active, nocturnally resting women in Würzburg, Federal Republic of Germany, gave blood at 0700, 1000, 1300, 1600, 1900, and 2200 for radioimmunoassay of aldosterone. Single and population-mean cosinors were applied. A multivariate analysis of circadian rhythm characteristics revealed effects of age on the amplitude (p = .003) but not the mesor of aldosterone in women (i.e., the age effect could only be detected at certain circadian times but not at others). No change with age was found for concomitantly sampled men. Statistically significant interactions among circadian time, age, and sex (p = .001) establish the adrenocorticopause in women and suggest that it may occur earlier in women than in men, in keeping with similar results on serum cortisol in the same subjects. This phenomenon awaits scrutiny from the viewpoint of its bearing on longevity and life quality. These results also indicate the importance of assessing chronobiological characteristics.