Increasing age is associated with a reduction in overall heart rate variability as well as changes in complexity of physiologic dynamics. The aim of this study was to verify if the alterations in autonomic modulation of heart rate caused by the aging process could be detected by Shannon entropy (SE), conditional entropy (CE) and symbolic analysis (SA). Complexity analysis was carried out in 44 healthy subjects divided into two groups: old (n = 23, 63 ± 3 years) and young group (n = 21, 23 ± 2). It was analyzed SE, CE [complexity index (CI) and normalized CI (NCI)] and SA (0V, 1V, 2LV and 2ULV patterns) during short heart period series (200 cardiac beats) derived from ECG recordings during 15 min of rest in a supine position. The sequences characterized by three heart periods with no significant variations (0V), and that with two significant unlike variations (2ULV) reflect changes in sympathetic and vagal modulation, respectively. The unpaired t test (or Mann-Whitney rank sum test when appropriate) was used in the statistical analysis. In the aging process, the distributions of patterns (SE) remain similar to young subjects. However, the regularity is significantly different; the patterns are more repetitive in the old group (a decrease of CI and NCI). The amounts of pattern types are different: 0V is increased and 2LV and 2ULV are reduced in the old group. These differences indicate marked change of autonomic regulation. The CE and SA are feasible techniques to detect alteration in autonomic control of heart rate in the old group.

The effects of the aging process and an active life-style on the autonomic control of heart rate (HR) were investigated in nine young sedentary (YS, 23 ± 2.4 years), 16 young active (YA, 22 ± 2.1 years), 8 older sedentary (OS, 63 ± 2.4 years) and 8 older active (OA, 61 ± 1.1 years) healthy men. Electrocardiogram was continuously recorded for 15 min at rest and for 4 min in the deep breathing test, with a breath rate of 5 to 6 cycles/min in the supine position. Resting HR and RR intervals were analyzed by time (RMSSD index) and frequency domain methods. The power spectral components are reported in normalized units (nu) at low (LF) and high (HF) frequency, and as the LF/HF ratio. The deep breathing test was analyzed by the respiratory sinus arrhythmia indices: expiration/inspiration ratio (E/I) and inspiration-expiration difference (∆IE). The active groups had lower HR and higher RMSSD index than the sedentary groups (life-style condition: sedentary vs active, P < 0.05). The older groups showed lower HFnu, higher LFnu and higher LF/HF ratio than the young groups (aging effect: young vs older, P < 0.05). The OS group had a lower E/ I ratio (1.16) and ∆IE (9.7 bpm) than the other groups studied (YS: 1.38, 22.4 bpm; YA: 1.40, 21.3 bpm; OA: 1.38, 18.5 bpm). The interaction between aging and life-style effects had a P < 0.05. These results suggest that aging reduces HR variability. However, regular physical activity positively affects vagal activity on the heart and consequently attenuates the effects of aging in the autonomic control of HR.

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ResumoA queda em idosos é resultado de uma interação complexa entre fatores intrínsecos e extrínsecos. Embora seja difícil separar esses fatores, estudos apontam que fatores de risco ambientais estão presentes em aproximadamente 40% das quedas. O objetivo deste estudo foi realizar uma revisão sistemática da literatura sobre o envolvimento de fatores ambientais nas quedas em idosos vivendo na comunidade. Para tanto, foram selecionados estudos publicados no período de janeiro de 2000 a maio de 2014 nas bases de dados eletrônicas MEDLINE, LILACS e SciELO. Apenas artigos disponíveis na íntegra e em inglês, português e espanhol foram considerados para esta revisão. Após a análise do título, do resumo e do texto na íntegra, dez artigos foram incluídos na revisão. Nos estudos analisados, aproximadamente metade das quedas ocorreu durante a locomoção e envolveu tropeços e escorregões. Os fatores de risco ambientais estão muito presentes nas quedas (20-58%), sendo que superfícies irregulares, superfícies molhadas/escorregadias, objetos/tapetes soltos e desníveis no chão/problemas com degraus foram os mais prevalentes. Observou-se tendência de aumento na ocorrência de quedas em ambientes externos, as quais são frequentemente precipitadas por fatores extrínsecos. Mais estudos são necessários na caracterização e no desenvolvimento de estratégias de prevenção de quedas em ambientes externos. AbstractFalls in the elderly is the result of a complex interplay between intrinsic and extrinsic factors. Although it is difficult to separate these factors, studies indicate that environmental hazards are involved in approximately 40% of the falls. This study aimed to conduct a systematic review about the contribution of environmental hazards for falls in community-dwelling elderly. Studies published from January 2000 to May 2014 in the electronic databases MEDLINE, LILACS and SciELO were selected. Only free full-text articles written in English, Portuguese and Spanish were considered Palavras-chave: Acidentes por Quedas. Idoso. Medicina Ambiental.http://dx