Disparate circadian variations of blood pressure and body temperature in bedridden elderly patients with cerebral atrophy

Abstract

Twenty bedridden elderly patients with normal sleep-wake cycles were studied to evaluate the circadian variations of blood pressure, pulse rate, body core temperature, cortisol, and catecholamines with a focus on their relation to cerebral atrophy. Twenty-four-hour blood pressure (BP) and pulse rate monitorings were done with simultaneous measurement of urinary bladder temperature. Urine was also collected every 4 h to measure 17-hydroxycorticosterone and catecholamines. Based on the brain CT, frontal horn index (FHI: maximal distance between bilateral frontal horns/the corresponding width of the skull) was calculated as an index of cerebral atrophy. Analysis by the cosinor method revealed that the significant circadian rhythm with nocturnal decline was observed in only 9 patients (45%) for BP and in 13 patients (65%) for pulse rate. In contrast, 19 of 20 patients (95%) showed significant circadian rhythms of bladder temperature, with the nadirs appearing between 00:06 and 06:54. In the subgroup of mild cerebral atrophy (FHI < 0.30, n = 11), BP and pulse rate fell modestly but significantly during nighttime, whereas they did not fall in the subgroup of moderate to severe cerebral atrophy (FHI > or = 0.30, n = 9). The possibility could not be excluded that the sleep disturbance might result in the relatively high BP during nighttime. Bladder temperature, 17-hydroxycorticosteroids, and catecholamines showed significant nocturnal falls in both groups. In conclusion, nocturnal fall of BP disappeared in the bedridden elderly patients with cerebral atrophy, which cannot be explained by the change in the circadian variation of the sympathetic nervous system, cortisol, or body core temperature.