Decreases in urine specific gravity and urinary creatinine in elderly women

To examine the effects of aging on urinary levels of creatinine (CR) and urine specific gravity (SG) among women in a large-scale epidemiology survey.

Data on CR and SG in urine, together with smoking habits and menopausal status, were selected from previously established databases and combined with the results of supplemental sample collection. In total, CR and SG data were available for 11,090 never-smoking women (total group; 29-80 years of age); a subgroup of 1,851 women who lived in Kyoto was also selected from the total group. Data from the two groups were subjected to statistical analyses. In statistical evaluation, SG was converted to factor G, which was defined as (SG-1.000)x1,000.

Classification by decade of years of age showed that both CR and SG decreased steadily as a function of advancement in age over 30 years, both in the total group and in the Kyoto subgroup, showing high reproducibility of the observation on a whole-country basis and on a local basis. When the levels at 80 years of age were compared with those at 30 years, there was an approximately 60% and 30% decrease in CR and factor G, respectively. Thus, the effects of aging were more marked on CR than on factor G (and therefore on SG). Menopause appeared to be an influential factor in the reduction of CR and SG, separately from aging itself.

Urinary levels of creatinine and, to a lesser extent, urine specific gravity, steadily decreased as a function of ages of over 30 years in women.