Low ambient temperatures are particularly harmful to the elderly and in the winter in the UK temperatures in some dwellings may fall to 6 degrees C. The World Health Organization recommends a minimal indoor temperature of 18 degrees C and a 2-3 degrees C warmer minimal temperature for rooms occupied by sedentary elderly, young children and the handicapped. Below 16 degrees C, resistance to respiratory infections may be diminished. Both low and high relative humidities promote respiratory illnesses. At temperatures below 12 degrees C, cold extremities and slight lowering of core temperature can induce short-term increases in blood pressure. Raised blood pressure and increased blood viscosity in moderate cold may be important causal factors in the increased winter morbidity and mortality due to heart attacks and strokes. Deep body temperature does not usually fall until resting clothed elderly people are exposed for two or more hours to an ambient temperature of 9 degrees C or below. Statistics available for the UK population do not support the view that there are large numbers of elderly people suffering from clinical hypothermia, though there may be a larger number in whom hypothermia is undiagnosed when the condition occurs secondary to other disorders.

353between the degree of severity of anaemia and of ventricular dilatation.If congestive cardiomyopathy in chronically uraemic patients on dialysis is a syndrome of homogeneous origin and similar evolution in all cases then an intensified search for the factors that may cause it is indicated. In this way the syndrome could be diagnosed at an early stage and treated. Greco, F, et al, Circulation, 1969, 40, 87. 26 Mason, D T, American Journal of Cardiology, 1973, 32, 437. 27 Grant, C, et al, American3Journal of Medicine, 1965Medicine, , 39, 1969 (Accepted 7 December 1976) CONDENSED REPORT Accidental hypothermia and impaired temperature homoeostasis in the elderly K J COLLINS, CAROLINE DORE, A N EXTON-SMITH, R H FOX, I C MACDONALD, PATRICIA M WOODWARD British Medical Journal, 1977, 1, 353-356 Summary A longitudinal study of the age-related decline in thermoregulatory capacity was made in 47 elderly people to try to identify those at risk from spontaneous hypothermia. During the winters of 1971-2 and 1975-6 environmental and body temperature profiles were obtained in the home, and thermoregulatory function was investigated by cooling and warming tests. Environmental temperature and socioeconomic conditions had not changed but the body core-shell temperature gradients were smaller in 1976, indicating progressive thermoregulatory impairment. People at risk of developing hypothermia also seem to have low resting peripheral blood flows, a non-

A study of 17 elderly men and 13 young adults of similar body build and wearing equivalent clothing insulation (0-8 clo) showed that when given control over their environment the elderly preferred the same mean comfort temperature (22-23°C) but manipulated ambient temperature much less precisely than the young. Slow adjustment of ambient temperature was related in some cases to a higher temperature-discrimination threshold.These findings suggest that both physiological and behavioural changes contribute to the increased vulnerability of old people in cold conditions. IntroductionOf the many factors contributing to hypothermia in old people, two appear to have physiological importance. One is the agerelated decline in the efficiency of cold-defence mechanisms'-3 and the other the reduced ability to detect temperature change.2-4 Studies of thermal-comfort requirements of healthy elderly people and young adults suggest, however, that the

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Mean deep body temperature fell by 0.4 +/- 0.1 (SD) degrees C in five sedentary, clothed 63-70 year old men and by 0.1 +/- 0.1 degrees C in four young adults after 2 h exposure in still air at 6 degrees C (P less than 0.001). The mean increase in systolic and diastolic pressure was significantly greater (P less than 0.002) in the older subjects (24 +/- 4 mmHg systolic, 13 +/- 4 mmHg diastolic) than in the young (14 +/- 6 mmHg systolic, 7 +/- 3 mmHg diastolic) after 2 h at 6 degrees C. A small rise in blood pressure occurred in the older men at 12 degrees C, but there was no increase in either group at 15 degrees C. The association of variables is particularly marked between systolic blood pressure and core temperature changes at 6 degrees C. There were no appreciable cold-adaptive changes in blood pressure or thermoregulatory responses after 7-10 days repeated exposure to 6 degrees C for 4 h each day. Blood pressure elevation in the cold was slower but more marked in the older men. These changes in blood pressure may provide a possible basis for delineating low domestic limiting temperature conditions.