Calcium metabolism in healthy men deprived of sunlight

Changes in urine parameters after desert exposure: assessment of stone risk in United States Marines transiently exposed to a desert environment

PURPOSE

Living in a desert environment has been associated with a higher incidence of kidney stone formation, likely because of concentrated urine output, higher production of vitamin D and genetic predisposition. We determined the changes in urinary parameters after a group of United States Marines temporarily transitioned from a temperate environment to a desert environment.

MATERIALS AND METHODS

A total of 50 Marines completed a questionnaire and performed 3, 24-hour urine collections before mobilization to the desert, after 30 days in the desert and 2 weeks after returning from the desert.

RESULTS

Daily urine output decreased 68% to 0.52 L despite marked increased fluid intake (17 L per day). Total daily urinary excretion of calcium, uric acid, sodium, magnesium and potassium in the desert decreased by 70%, 41%, 53%, 22% and 36%, respectively. Urinary pH decreased from 6.1 to 5.6 while in the desert, and citrate and oxalate had minimal changes. After their return from the desert, apart from a decrease of 22% in oxalate, there were no statistically significant differences from baseline. While in the desert, relative supersaturation risks of uric acid and sodium urate were increased 153% and 56%, respectively. Brushite relative supersaturation decreased 24%. After their return there was no statistical difference from baseline.

CONCLUSIONS

Our findings suggest that the kidneys preserved water and electrolytes while the Marines were subjected to the desert environment. Despite this conservation, relative saturations indicate increased risk of stones in healthy men exposed to a desert environment with rapid resolution upon return.

The clinical importance of environmental lighting to the elderly

1. Nurses need to be aware of the effects of artificial lights on the aged because the aged spend a greater amount of time under these lights than do younger people. 2. Although the aged require more light than younger people to see, bright lights may cause glare. The use of indirect lighting is recommended to reduce problems with glare. 3. The aged see best under artificial lighting that simulates natural sunlight. 4. Nurses who work in institutional settings should be sensitive to the need for individualized light-dark cycles.