Plasma osmolality in an elderly population.

Plasma osmolality was calculated for 303 subjects (152 male and 151 female; mean age 70 +/- 11 years) living in the community. The distribution was normal, and it was not influenced by age, sex, smoking, alcohol intake or use of diuretics. The mean and 95% CI from this study were very close to the reference range given in the Geigy Scientific Tables. Higher values of mean plasma osmolality and wider 95% CI found in previous studies of unselected elderly subjects may simply reflect the higher prevalence of diseases in the elderly.