Unipolar relatives in bipolar pedigrees: a search for elusive indicators of underlying bipolarity.

In an effort to identify features indicative of underlying bipolarity within the unipolar relatives of bipolar probands, we compared unipolar relatives of bipolars with unipolar relatives of controls. Using data from the Yale-NIMH Collaborative Study of Depression, we compared a number of demographic and clinical features individually, and then developed a logistic regression model for the differences found. Unipolar relatives of bipolars were generally similar to relatives of controls, but they were older and more likely to suffer from more severe, even psychotic, depression, and somewhat less likely to report a brief transition into their illness. A multiple logistic regression model for observed differences was highly statistically significant, but had limited ability to discriminate effectively between the two groups. These findings suggest that more stringent diagnostic criteria might be beneficial if unipolar relatives are counted as affected in linkage studies of bipolar disorder. The ability of this strategy to improve the "clinical phenotype" is limited, however, and other approaches may be needed to identify features of underlying bipolarity and thus to define "caseness" for unipolar relatives in linkage analyses of bipolar disorder.

Effect of a face mask on respiratory water loss during sleep in cold conditions.

The purpose of this study was to test the hypothesis that a heat-and-moisture-retaining mask would result in a significant decrease in respiratory water loss among healthy subjects sleeping in a cold environment. The study was done in a backyard near a tertiary-care center during winter nights with ambient temperatures of less than 0 degrees C. Subjects were 10 healthy volunteers, 8 males and 2 females, aged 23-40 years, with a mean of 30.9 years. In a crossover design study, subjects slept alone in mountaineering tents on two nights (8 h each night) using sleeping bags and ground insulation. On one night, they wore heat-and-moisture-retaining masks designed for cold weather exercise. On the other night, they wore no mask. Subjects were weighed before and after each session to obtain an estimate of respiratory water loss. Comparisons were made of weight loss with and without the mask. We found the use of the masks resulted in decreased weight loss in all but one subject. The mean reduction in weight loss was 0.13 kg (SD +/- 0.18 kg). Using a one-tailed t-test, this difference was found to be significant (p < .05). We conclude that the use of a simple and inexpensive face mask can result in a meaningful decrease in overnight respiratory water loss while sleeping in a cold environment.