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Abstract

Objective We aimed to determine whether there is a seasonal variation of out-of-hospital cardiac arrests (OHCA) in an equatorial climate, which does not experience seasonal environmental change. Methods We conducted an observational prospective study looking at the occurrence of OHCA in Singapore. Included were all patients with OHCA presented to Emergency Departments across the country. We examined the monthly, daily, and hourly number of cases over a three-year period. Data was analyzed using analysis of variance (ANOVA). Results From October, 1st 2001 to October, 14th 2004, 2428 patients were enrolled in the study. Mean age for cardiac arrests was 60.6 years with 68.0% male. Ethnic distribution was 69.5% Chinese, 15.0% Malay, 11.0% Indian, and 4.4% Others. There was no significant seasonal variation (spring/summer/fall/winter) of events (ANOVA P = 0.71), monthly variation (P = 0.88) or yearly variation (P = 0.26). We did find weekly peaks on Mondays and a circadian pattern with daily peaks from 9–10 am. Conclusions We did not find any discernable seasonal pattern of cardiac arrests. This contrasts with findings from temperate countries and suggests a climatic influence on cardiac arrest occurrence. We also found that sudden cardiac arrests follow a circadian pattern.

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Human responses to the geophysical daily, annual and lunar cycles.

Till Roenneberg, Diana Foster (2008)

Collectively the daily, seasonal, lunar and tidal geophysical cycles regulate much of the temporal biology of life on Earth. The increasing isolation of human societies from these geophysical cycles, as a result of improved living conditions, high-quality nutrition and 24/7 working practices, have led many to believe that human biology functions independently of them. Yet recent studies have highlighted the dominant role that our circadian clock plays in the organisation of 24 hour patterns of behaviour and physiology. Preferred wake and sleep times are to a large extent driven by an endogenous temporal program that uses sunlight as an entraining cue. The alarm clock can drive human activity rhythms but has little direct effect on our endogenous 24 hour physiology. In many situations, our biology and our society appear to be in serious opposition, and the damaging consequences to our health under these circumstances are increasingly recognised. The seasons dominate the lives of non-equatorial species, and until recently, they also had a marked influence on much of human biology. Despite human isolation from seasonal changes in temperature, food and photoperiod in the industrialised nations, the seasons still appear to have a small, but significant, impact upon when individuals are born and many aspects of health. The seasonal changes that modulate our biology, and how these factors might interact with the social and metabolic status of the individual to drive seasonal effects, are still poorly understood. Lunar cycles had, and continue to have, an influence upon human culture, though despite a persistent belief that our mental health and other behaviours are modulated by the phase of the moon, there is no solid evidence that human biology is in any way regulated by the lunar cycle.

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Diurnal, weekly and seasonal variation of sudden death. Population-based analysis of 24,061 consecutive cases.

S Willich, Anja C Schreiber, H-R Arntz … (2000)

Several studies have reported circadian and seasonal variations in acute cardiovascular disease. In addition, a weekly variation has been observed in acute myocardial infarction. The aim of our study was to determine the circadian weekly, and seasonal variations of sudden death utilizing population-based data. We analysed the emergency medical system data of Berlin (West) from 1987-1991 with respect to all consecutive sudden deaths in subjects >18 years (n=24 061). There was a marked circadian variation of sudden death, with a minimum between 0 and 6 h and a maximum between 6 and 12 h (P 65 (15.7%). In addition, we found a significant seasonal variation (P 65 years. The present analyses demonstrate marked variations in the occurrence of sudden death with peaks during morning hours, on Mondays, and during winter months. The findings suggest that the onset of sudden death may be associated with endogenous rhythms and external factors including climatic conditions. Copyright 2000 The European Society of Cardiology.

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Seasonal variations of plasma fibrinogen and factor VII activity in the elderly: winter infections and death from cardiovascular disease.

K Khaw, S P Woodhouse, T. Meade … (1994)

There are approximately 20,000 excess deaths from cardiovascular disease each winter in England and Wales. The reasons for the excess have not been fully elucidated. For one year, we studied 96 men and women aged 65-74 living in their own homes in order to examine seasonal variation in plasma fibrinogen and factor VII clotting activity (FVIIc), and to investigate relationships with infection and other cardiovascular-disease risk factors. Both fibrinogen and FVIIc plasma values were greater in winter with estimated winter-summer differences (confidence intervals) of 0.13 (0.05-0.20) g/L for fibrinogen and 4.2 (1.2-7.1)% of standard for FVIIc. These differences could account for 15% and 9% increases in ischaemic heart disease risk in winter respectively. After adjustment for confounding by season, fibrinogen was strongly related to neutrophil count (p < 0.0001), C-reactive protein (p < 0.0001), alpha 1-antichymotrypsin (p < 0.0001), and self-reported cough (p < 0.0001) and coryza (p = 0.0004), but not to ambient temperature. Therefore, we suggest that seasonal variation in fibrinogen might be induced by winter respiratory infections via activation of the acute phase response. Seasonal variations in the cardiovascular risk factors fibrinogen and FVIIc provide further possible explanations for the marked seasonal variation in death from ischaemic heart disease and stroke in the elderly.

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PubMed ID:: 27147836

PMC ID:: 4806825

DOI:: 10.2147/oaem.s9266

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Keywords: cardiopulmonary resuscitation,cardiac arrest,seasonal pattern,circadian pattern

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Keywords: cardiopulmonary resuscitation, cardiac arrest, seasonal pattern, circadian pattern

Temporal variation of out-of-hospital cardiac arrests in an equatorial climate

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Most cited references 43

Human responses to the geophysical daily, annual and lunar cycles.

Diurnal, weekly and seasonal variation of sudden death. Population-based analysis of 24,061 consecutive cases.

Seasonal variations of plasma fibrinogen and factor VII activity in the elderly: winter infections and death from cardiovascular disease.

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