Disruption of diurnal rhythm in the elderly

In his May 1 commentary1Lye M Rhythm of life and vicissitudes of old age.Lancet. 1999; 353: 1461-1462Summary Full Text Full Text PDF PubMed Scopus (5) Google Scholar Michael Lye comments on disruption of diurnal rhythm and nocturia in the elderly. Disrupted pattern of diurnal blood pressure variation is associated with clinically overt and silent target-organ damage, and is hypothesised to be a predictor of subsequent cardiovascular events independent of high blood pressure level.2Pickering TG The clinical significance of diurnal blood pressure variations: dippers and non-dippers.Circulation. 1990; 81: 700-702Crossref PubMed Scopus (370) Google Scholar, 3O'Brien E Sheridan J O'Malley K Dippers and non-dippers.Lancet. 1998; 13: 397Google Scholar, 4Verdecchia P Porcellati C Schillaci G et al.Ambulatory blood pressure: an independent predictor of prognosis in essential hypertension.Hypertension. 1994; 24: 793-801Crossref PubMed Scopus (1662) Google Scholar The non-dipper, with diminished nocturnal blood pressure decline, has been proposed as one subtype of abnormal diurnal blood pressure variation that is associated with increased occurrence of damage to all target organs (brain, heart, and kidney) and poorer prognosis for cardiovascular events, when compared with dippers with appropriate nocturnal blood pressure fall.2Pickering TG The clinical significance of diurnal blood pressure variations: dippers and non-dippers.Circulation. 1990; 81: 700-702Crossref PubMed Scopus (370) Google Scholar, 3O'Brien E Sheridan J O'Malley K Dippers and non-dippers.Lancet. 1998; 13: 397Google Scholar, 4Verdecchia P Porcellati C Schillaci G et al.Ambulatory blood pressure: an independent predictor of prognosis in essential hypertension.Hypertension. 1994; 24: 793-801Crossref PubMed Scopus (1662) Google Scholar Although the precise mechanism of this non-dipping status remains unclear, the frequency of non-dipping pattern increases with age, reaching 50% in elderly people. We found that nocturnal physical activity was increased in non-dippers compared with those with a normal nocturnal blood pressure fall.5Kario K, Schwartz JE, Pickering TG. Ambulatory physical activity as a determinant of diurnal blood pressure variation. Hypertension (in press).Google Scholar This increased physical activity may be partly due to nocturnal behaviour (eg, going to the bathroom, getting a drink of water) and poor sleep quality. In addition to the possibility that increased physical activity indicates poor sleep quality and an increased occurrence of unconscious micro-arousals that trigger sympathetic activation, increased physical activity per se may activate autonomic nervous function to modulate endocrine function. These neurohumoral changes could lead to non-dipping. Thus, especially for non-dippers who have disrupted diurnal rhythm, improvement of sleep quality and a decline in nocturnal behaviour might reduce physical activity-related increase in nocturnal blood pressure, resulting in a more normal diurnal rhythm, which might also reduce the risk of cardiovascular disease in elderly people.