Diurnal and seasonal variation of stroke incidence in patients with cardioembolic stroke due to atrial fibrillation

Time of the day and season distribution among stroke code subtypes: differences between ischemic stroke, intracranial hemorrhage, and stroke mimic

Background

Circadian variations in the timing of the onset of stroke symptoms have been described, showing a morning excess of cardiovascular risk. To date, no differences have been found between stroke subtype and time distribution throughout the day. The present study aims to compare the seasonal and circadian rhythm of symptoms onset in ischemic, hemorrhagic, and stroke mimic patients.

Methods

This study was conducted prospectively at a hospital and involved a cohort of stroke alert patients from 2018 to 2021. Stroke subtypes were classified as ischemic stroke, intracerebral hemorrhage (ICH), transient ischemic attack (TIA), and stroke mimic. Clinical variables were recorded, and each patient was assigned to a 4-h interval of the day according to the time of onset of symptoms; unwitnessed stroke patients were analyzed separately. Seasonal changes in stroke distribution were analyzed at 3-month intervals.

Results

A total of 2,348 patients were included in this analysis (ischemic 67%, ICH 13%, mimic 16%, and TIA 3%). Regardless of stroke subtype, most of the patients were distributed between 08-12 h and 12-16 h. Significant differences were found in the time distribution depending on stroke subtype, with ICH predominating in the 4-8 h period (dawn), most of which were hypertensive, TIA in the 12-16 h period (afternoon), and stroke mimic in the 20 h period (evening). The ischemic stroke was evenly distributed throughout the different periods of the day. There were no differences in the seasonal pattern between different stroke subtypes, with winter being the one that accumulated the most cases.

Conclusion

The present study showed different circadian patterns of stroke subtypes, with a predominance of ICH at dawn and stroke mimic in the afternoon. The stroke circadian rhythm resembles previous studies, with a higher incidence in the morning and a second peak in the afternoon.

Seasonal Variations in Stroke and a Comparison of the Predictors of Unfavorable Outcomes among Patients with Acute Ischemic Stroke and Cardioembolic Stroke

We investigated the seasonal variations in stroke in 4040 retrospectively enrolled patients with acute ischemic stroke (AIS) admitted between January 2011 and December 2022, particularly those with cardioembolic (CE) stroke, and compared predictors of unfavorable outcomes between AIS patients and CE stroke patients. The classification of stroke subtypes was based on the Trial of ORG 10172 in Acute Stroke Treatment. Stroke occurrence was stratified by seasons and weekdays or holidays. Of all AIS cases, 18% were of CE stroke. Of all five ischemic stroke subtypes, CE stroke patients were the oldest; received the most thrombolysis and thrombectomy; had the highest initial National Institutes of Stroke Scale (NIHSS) and discharge modified Rankin Scale (mRS) scores; and had the highest rate of in-hospital complications, unfavorable outcomes (mRS > 2), and mortality. The highest CE stroke prevalence was noted in patients aged ≥ 85 years (30.9%); moreover, CE stroke prevalence increased from 14.9% in summer to 23.0% in winter. The main predictors of death in patients with CE stroke were age > 86 years, heart rate > 79 beats/min, initial NIHSS score > 16, neutrophil-to-lymphocyte ratio (NLR) > 6.4, glucose > 159 mg/dL, cancer history, in-hospital complications, and neurological deterioration (ND). The three most dominant factors influencing death, noted in not only patients with AIS but also those with CE stroke, are high initial NIHSS score, ND, and high NLR. We selected the most significant factors to establish nomograms for predicting fatal outcomes. Effective heart rhythm monitoring, particularly in older patients and during winter, may help develop stroke prevention strategies and facilitate early AF detection.

Is there a circannual variation in the anticoagulation control of warfarin?

BACKGROUND

The literature regarding the seasonal variation in the therapeutic response to warfarin is somewhat contradictory, with several discrepancies. We assessed the influence of seasons on various pharmacodynamic indices of warfarin.

METHODS

A retrospective study was carried out in adults receiving warfarin for at least 6 months. Details of their demographic characteristics, duration and dose of warfarin therapy and values of prothrombin time international normalised ratio (PT-INR) were retrieved. Standard definitions were followed for defining various seasons, time in therapeutic range (TTR), log-INR variability and warfarin sensitivity index (WSI). National Institute for Health and Care Excellence (NICE) criteria were used for defining TTR into good (≥65%) and poor (<65%) anticoagulation control.

RESULTS

Two hundred and four patients were recruited. Only a subtle statistically significant difference was observed between the numbers of patients in the various PT-INR categories. However, no significant intra-individual differences were observed in mean TTR. Similarly, the proportion of patients with poor anticoagulation control, high INR variability and high WSI was not significantly different between summer, transition period 1, winter and transition period 2.

CONCLUSION

No clinically significant seasonal variations were observed in the therapeutic response to warfarin.

Implications of Circadian Rhythm in Stroke Occurrence: Certainties and Possibilities

Stroke occurrence is not randomly distributed over time but has circadian rhythmicity with the highest frequency of onset in the morning hours. This specific temporal pattern is valid for all subtypes of cerebral infarction and intracerebral hemorrhage. It also correlates with the circadian variation of some exogenous factors such as orthostatic changes, physical activity, sleep-awake cycle, as well as with endogenous factors including dipping patterns of blood pressure, or morning prothrombotic and hypofibrinolytic states with underlying cyclic changes in the autonomous system and humoral activity. Since the internal clock is responsible for these circadian biological changes, its disruption may increase the risk of stroke occurrence and influence neuronal susceptibility to injury and neurorehabilitation. This review aims to summarize the literature data on the circadian variation of cerebrovascular events according to physiological, cellular, and molecular circadian changes, to survey the available information on the chronotherapy and chronoprophylaxis of stroke and its risk factors, as well as to discuss the less reviewed impact of the circadian rhythm in stroke onset on patient outcome and functional status after stroke.

Association between Atrial Fibrillation Incidence and Temperatures, Wind Scale and Air Quality: An Exploratory Study for Shanghai and Kunming

As a common cardiovascular disease, atrial fibrillation has the characteristics of high morbidity, high disability, and high fatality rates, seriously endangering human health and sustainability. Some research has confirmed that environmental factors are related to the risk of illness and death from cardiovascular diseases (including atrial fibrillation), while there is still little comparison on the situation of the two cities in China. This research uses medical data in Shanghai and Kunming establishing, through two-step research, logistic models to compare the impacts on atrial fibrillation incidence to figure out the association between environmental factors (including air pollution, weather, temperature, and wind scales) and atrial fibrillation. Finally, this research shows that environmental impacts on atrial fibrillation prevalence have generality, regionality, and lagging characteristics. The result is significant for atrial fibrillation patients and provides a reliable medical theory basis for nursing measures. Besides, this research provides a prospective method of offering early warning for potential atrial fibrillation patients, helping to maintain human beings’ sustainable development.

Seasonal Variations in the Incidence of Ischemic Stroke, Extracranial and Intracranial Hemorrhage in Atrial Fibrillation Patients

BACKGROUND

Ischemic stroke (IS) and major bleeding, which are serious adverse events in patients with atrial fibrillation (AF), could have seasonal variations, but there are few reports.Methods and Results:In the Shinken Database 2004-2016 (n=22,018), 3,581 AF patients (average age, 63.5 years; 2,656 men, 74.2%; 1,388 persistent AF, 38.8%) were identified. Median CHADS₂and HAS-BLED scores were both 1 point. Oral anticoagulants were prescribed for 2,082 (58.1%) patients (warfarin, 1,214; direct oral anticoagulants [DOACs], 868). Incidence and observation period (maximum 3 years) of IS, extracranial hemorrhage (ECH), and intracranial hemorrhage (ICH) were counted separately for the northern hemisphere seasons. During the mean follow-up period of 2.4 years, there were totals of 90 IS, 73 ECH, and 33 ICH cases. The respective incidence rates per 1,000 patient-years in spring, summer, autumn, and winter were 8.5, 8.8, 7.5, and 16.8 for IS, 7.2, 9.7, 3.8, and 13.1 for ECH, and 2.7, 1.9, 3.8, and 7.0 for ICH. The number of patients with DOACs relatively increased among those with ECH in summer.

CONCLUSIONS

Significant seasonal variations were observed for IS, ECH, and ICH events in AF patients, and were consistently the highest in winter. A small peak of ECH was observed in summer, which seemed, in part, to be related to increased DOAC use.

Circadian variation and seasonal distribution of implantable defibrillator detected new onset atrial fibrillation

BACKGROUND

We aimed to characterize the hourly, daily, and seasonally variations in the detection of new atrial fibrillation (AF) in heart failure patients implanted with a defibrillator.

METHODS

In 1309 patients enrolled in MADIT-RIT without AF at baseline, atrial arrhythmia data were analyzed from device interrogations. The circadian, weekly, and seasonal distribution of device detected AF was evaluated. The morning period was defined as 06:00-11:59, afternoon as 12:00-16:59, evening as 17:00-22:59, and the nighttime as 23:00-05:59.

RESULTS

During 17 months of follow-up, 66 (5%) patients developed new device-detected AF. AF patients were less likely to have ischemic cardiomyopathy and were more likely to have received an implantable cardioverter defibrillator rather than a cardiac resynchronization therapy with defibrillator. The highest number of AF occurred during the evening hours (25 patients [38%]) followed by a second peak in AF detection during the afternoon hours (21 patients [32%]). Importantly during the nighttime, new AF occurred only in three patients (4%). In comparison with the nighttime period, the odds ratio (OR) of developing AF during the evening time period was 8.5-fold higher (95% CI 7.3-9.7, P < .01). Detection of AF during the spring and winter seasons accounted for 67% of all new device-detected AF.

CONCLUSIONS

There is diurnal and seasonal variation in new onset AF. A double peak in the incidence of AF is observed during the afternoon and evening hours, and during the spring and winter seasons. This information may be useful when deciding when to screen at-risk patients for new AF.

Population's health information-seeking behaviors and geographic variations of stroke in Malaysia: an ecological correlation and time series study

Stroke has emerged as a major public health concern in Malaysia. We aimed to determine the trends and temporal associations of real-time health information-seeking behaviors (HISB) and stroke incidences in Malaysia. We conducted a countrywide ecological correlation and time series study using novel internet multi-timeline data stream of 6,282 hit searches and conventional surveillance data of 14,396 stroke cases. We searched popular search terms related to stroke in Google Trends between January 2004 and March 2019. We explored trends by comparing average relative search volumes (RSVs) by month and weather through linear regression bootstrapping methods. Geographical variations between regions and states were determined through spatial analytics. Ecological correlation analysis between RSVs and stroke incidences was determined via Pearson's correlations. Forecasted model was yielded through exponential smoothing. HISB showed both cyclical and seasonal patterns. Average RSV was significantly higher during Northeast Monsoon when compared to Southwest Monsoon (P < 0.001). "Red alerts" were found in specific regions and states. Significant correlations existed within stroke related queries and actual stroke cases. Forecasted model showed that as HISB continue to rise, stroke incidence may decrease or reach a plateau. The results have provided valuable insights for immediate public health policy interventions.

Association of daytime napping with incident stroke in middle-aged and older adults: a large community-based study

BACKGROUND AND PURPOSE

There are conflicting reports on the association between daytime napping and incident stroke. This study was designed to investigate the relationship between daytime napping and stroke within a community-based cohort.

METHODS

The present prospective study was based on the Sleep Heart Health Study. Napping habits were assessed with a self-reported Sleep Habits Questionnaire. Participants with napping habits of different durations and frequencies were followed up until the first stroke occurred or the final censoring date. Cox proportional hazards models were used to estimate the relationship between napping habits and stroke.

RESULTS

A total of 4757 participants (2219 men, mean age 63.6 ± 11.1 years) were enrolled in this study. Compared with those taking no naps, multivariate proportional hazards models analysis indicated that individuals taking naps with a duration of >60 min [hazard ratio (HR), 2.460; 95% confidence interval (CI), 1.538-3.934] had a higher risk of stroke. There was also an increased risk of stroke among participants taking naps daily (HR, 1.563; 95% CI, 1.059-2.307) or five to six times/week (HR, 1.548; 95% CI, 1.026-2.335). After combining napping durations and frequencies, regular long naps (HR, 1.903; 95% CI, 1.182-3.065) and regular short naps (HR, 1.451; 95% CI, 1.010-2.084) were independent risk factors for incident stroke.

CONCLUSION

Daytime napping with a long duration (>30 min) or a high frequency (≥5 times/week) may increase the risk of stroke.

Seasonal variation in the risk of ischemic stroke in patients with atrial fibrillation: A nationwide cohort study

BACKGROUND

Several cardiovascular diseases exhibit seasonal variations, but data about cold temperature and risk of ischemic stroke in patients with atrial fibrillation (AF) are limited.

OBJECTIVE

The purpose of this study was to investigate the risk of ischemic stroke in different seasons, testing the hypothesis that the cold weather season would increase the risk of stroke in AF.

METHODS

This study used the National Health Insurance Research Database in Taiwan. From 2000 to 2012, a total of 289,559 AF patients were enrolled, and 34,991 experienced ischemic stroke after mean follow-up of 3 years. The relationship between risk of ischemic stroke and temperatures was analyzed.

RESULTS

The highest incidence of ischemic stroke was observed in winter, which was the coldest season, with an incidence rate of 0.33 per 100 person-months. Compared with the summer period, the risk of ischemic stroke increased by 10% in spring (incidence rate ratio [IRR] 1.10; 95% confidence interval [CI] 1.07-1.13) and by 19% in winter (IRR 1.19; 95% CI 1.15-1.22) but did not differ significantly between summer and autumn (IRR 1.00; 95% CI 0.97-1.03). Compared with the days with an average temperature of 30°C, the risk of ischemic stroke for days with an average temperature <20°C significantly increased. Lower 7-, 10-, or 14-day average temperatures were significantly associated with an increased risk of ischemic stroke in the case-crossover analysis.

CONCLUSION

In this nationwide study, a seasonal variation of incidence of ischemic stroke in AF patients was observed, with an increased risk of stroke on days with an average temperature <20°C. AF-related stroke may be influenced by environmental interactions.

Daily Variation in the Occurrence of Different Subtypes of Stroke

Three thousand two hundred and ninety-eight patients admitted to our Stroke Unit with hemorrhagic, large artery atherosclerosis, cardioembolic, small-vessel occlusion, and undetermined etiology-cryptogenic strokes were included in the study. The circadian variability in onset in each stroke subgroup and the associations with various risk factors were analyzed. In each subgroup, a significant minority of patients suffered from stroke during sleep. In the ischemic group, hypercholesterolemia, paroxysmal atrial fibrillation, and previous myocardial infarction facilitated the onset during waking. During waking, stroke onset was significantly higher in the morning compared to the afternoon both in the hemorrhagic and in the ischemic type. In hemorrhagic stroke, a previous stroke was associated with a lower early morning occurrence. In large artery atherosclerosis stroke, males were at higher risk of early morning occurrence (p < 0.01). In small-vessel occlusion stroke, hypertension is significantly more present in the morning compared to the afternoon onset (p < 0.005). Circadian patterns of stroke onset were observed both in hemorrhagic and in ischemic stroke, irrespective of the ischemic subgroup. In all groups, stroke was more likely to occur during waking than during sleep and, in the diurnal period, during morning than during afternoon. Moreover, sex and some clinical factors influence the diurnal pattern.

Higher ratio of ischemic stroke to hemorrhagic stroke in summer

BACKGROUND

The aim of this study was to investigate the seasonal variation of the ratio of hemorrhagic stroke to ischemic stroke. The working hypothesis is that the ratio may vary among seasons.

METHODS

A total of 13,788 patients registered in the Kyoto Stroke Registry from 1999 to 2009 were divided into 4 groups based on the season in which stroke developed. We calculated odds ratio (OR) for the incidence of stroke as a whole, cerebral infarction (CeI), cerebral hemorrhage (CH), and subarachnoid hemorrhage (SAH) in spring, autumn, and winter setting summer as a reference. Using a logistic regression, we evaluated the seasonal variation of ORs for CH/CeI and for SAH/CeI with adjustment for age, gender, and risk factors.

RESULTS

Incidence of CeI in autumn was lower than in summer (OR: 0.93; 0.87-0.98, P = 0.013). Incidence of CH was higher in spring (OR: 1.36; 1.23-1.49, P < 0.001), in autumn (OR: 1.16; 1.05-1.28, P = 0.004), and in winter (OR: 1.37; 1.25-1.51, P < 0.001) than in summer. Incidence of SAH was higher in spring (OR: 1.51; 1.28-1.79, P < 0.001) and in winter (OR: 1.44; 1.22-1.70, P < 0.001) than in summer. OR for CH/CeI in spring, autumn, and winter were 1.28 (1.13-1.45, P < 0.001), 1.26 (1.11-1.43, P < 0.001), and 1.35 (1.19-1.53, P < 0.001), respectively. ORs for SAH/CeI were 1.46 (1.19-1.79, P < 0.001), 1.34 (1.09-1.66, P = 0.007), and 1.50 (1.22-1.84, P < 0.001), respectively.

CONCLUSIONS

Seasonal variations differed among stroke subtypes. The OR for CH/CeI and for SAH/CeI was lower in summer and higher in the rest of seasons independent of age, gender, and risk factors.

Seasonal Variation in Paroxysmal Atrial Fibrillation: A Systematic Review

INTRODUCTION

A variety of cardiovascular diseases have been demonstrated to have seasonal variations with peaks in the winter and troughs in the summer. Studies regarding atrial fibrillation (AF) have had varying results and this review describes the current data regarding the seasonal variation of AF and mechanisms mediating this seasonal fluctuation.

METHODS

A systematic review was conducted of PubMed, EBSCO and OVID for manuscripts describing the association between seasonal variation and the occurrence of AF. Studies meeting eligibility criteria were assessed for quality and reporting bias. Data was extracted in regards to the following associations: seasonal variation and AF paroxysms, temperature and AFparoxysms, duration of daylight and AF paroxysms, barometric pressure and AF paroxysms, alcohol and AF paroxysms, as well as seasonal variation and AF related stroke.

RESULTS

A total of 15 studies were identified for inclusion. Of these, 11 studies assessed seasonal variation and the remaining 4 studies assessed seasonal variation in AF related stroke. AF paroxysms peaked in winter with a trough in summer. There was an inverse correlation between temperatures as well barometric pressure and the occurrence of AF paroxysms and a positive correlation with duration of daylight.

CONCLUSIONS

The rate of occurrence of paroxysmal AF varies by seasons and is greatest during winter and least in summer.

Consciousness level and off-hour admission affect discharge outcome of acute stroke patients: a J-ASPECT study

Background

Poor outcomes have been reported for stroke patients admitted outside of regular working hours. However, few studies have adjusted for case severity. In this nationwide assessment, we examined relationships between hospital admission time and disabilities at discharge while considering case severity.

Methods and Results

We analyzed 35 685 acute stroke patients admitted to 262 hospitals between April 2010 and May 2011 for ischemic stroke (IS), intracerebral hemorrhage (ICH), or subarachnoid hemorrhage (SAH). The proportion of disabilities/death at discharge as measured by the modified Rankin Scale (mRS) was quantified. We constructed 2 hierarchical logistic regression models to estimate the effect of admission time, one adjusted for age, sex, comorbidities, and number of beds; and the second adjusted for the effect of consciousness levels and the above variables at admission. The percentage of severe disabilities/death at discharge increased for patients admitted outside of regular hours (22.8%, 27.2%, and 28.2% for working‐hour, off‐hour, and nighttime; P<0.001). These tendencies were significant in the bivariate and multivariable models without adjusting for consciousness level. However, the effects of off‐hour or nighttime admissions were negated when adjusted for consciousness levels at admission (adjusted OR, 1.00 and 0.99; 95% CI, 1.00 to 1.13 and 0.89 to 1.10; P=0.067 and 0.851 for off‐hour and nighttime, respectively, versus working‐hour). The same trend was observed when each stroke subtype was stratified.

Conclusions

The well‐known off‐hour effect might be attributed to the severely ill patient population. Thus, sustained stroke care that is sufficient to treat severely ill patients during off‐hours is important.

Cold-related cardiorespiratory symptoms among subjects with and without hypertension: the National FINRISK Study 2002

BACKGROUND

Exposure to cold weather increases blood pressure (BP) and may aggravate the symptoms and influence the prognosis of subjects with a diagnosis of hypertension. We tested the hypothesis that subjects with hypertension alone or in combination with another cardiovascular disease (CVD) experience cold-related cardiorespiratory symptoms more commonly than persons without hypertension. This information is relevant for proper treatment and could serve as an indicator for predicting wintertime morbidity and mortality.

METHODS

A self-administered questionnaire inquiring of cold-related symptoms was obtained from 6591 men and women aged 25-74 yrs of the FINRISK Study 2002 population. BP was measured in association with clinical examinations. Symptom prevalence was compared between subjects with diagnosed hypertensive disease with (n = 395) or without (n = 764) another CVD, untreated diagnosed hypertension (n = 1308), measured high BP (n = 1070) and a reference group (n = 2728) with normal BP.

RESULTS

Hypertension in combination with another CVD was associated with increased cold-related dyspnoea (men: adjusted odds ratio 3.94, 95% confidence interval 2.57-6.02)/women: 4.41, 2.84-6.86), cough (2.64, 1.62-4.32/4.26, 2.60-6.99), wheezing (2.51, 1.42-4.43/;3.73, 2.08-6.69), mucus excretion (1.90, 1.24-2.91/2.53, 1.54-4.16), chest pain (22.5, 9.81-51.7/17.7, 8.37-37.5) and arrhythmias (43.4, 8.91-211/8.99, 3.99-20.2), compared with the reference group. Both diagnosed treated hypertension and untreated hypertension and measured high BP resulted in increased cardiorespiratory symptoms during the cold season.

CONCLUSION

Hypertension alone and together with another CVD is strongly associated with cold-related cardiorespiratory symptoms. As these symptoms may predict adverse health events, hypertensive patients need customized care and advice on how to cope with cold weather.

Modeling gradually changing seasonal variation in count data using state space models: a cohort study of hospitalization rates of stroke in atrial fibrillation patients in Denmark from 1977 to 2011

BACKGROUND

Seasonal variation in the occurrence of cardiovascular diseases has been recognized for decades. In particular, incidence rates of hospitalization with atrial fibrillation (AF) and stroke have shown to exhibit a seasonal variation. Stroke in AF patients is common and often severe. Obtaining a description of a possible seasonal variation in the occurrence of stroke in AF patients is crucial in clarifying risk factors for developing stroke and initiating prophylaxis treatment.

METHODS

Using a dynamic generalized linear model we were able to model gradually changing seasonal variation in hospitalization rates of stroke in AF patients from 1977 to 2011. The study population consisted of all Danes registered with a diagnosis of AF comprising 270,017 subjects. During follow-up, 39,632 subjects were hospitalized with stroke. Incidence rates of stroke in AF patients were analyzed assuming the seasonal variation being a sum of two sinusoids and a local linear trend.

RESULTS

The results showed that the peak-to-trough ratio decreased from 1.25 to 1.16 during the study period, and that the times of year for peak and trough changed slightly.

CONCLUSION

The present study indicates that using dynamic generalized linear models provides a flexible modeling approach for studying changes in seasonal variation of stroke in AF patients and yields plausible results.

Seasonality, incidence and prognosis in atrial fibrillation and stroke in Denmark and New Zealand

OBJECTIVES

There are relatively few large studies of seasonal variation in the occurrence of stroke in patients with atrial fibrillation (AF). We investigated the seasonal variation in incidence rates of hospitalisation with stroke in patients from Denmark and New Zealand.

DESIGN

Cohort study.

SETTING

Nationwide hospital discharge data from Denmark and New Zealand.

PARTICIPANTS

243 381 (median age 75) subjects having a first-time hospitalisation with AF in Denmark and 51 480 (median age 76) subjects in New Zealand constituted the study population. Subjects with previous hospitalisation with stroke were excluded. PRIMARY AND SECONDARY EFFECT MEASURES: Peak-to-trough ratio of the seasonal variation in incidence rates of stroke in AF patients adjusted for an overall trend was primary effect measure and was assessed using a log-linear Poisson regression model. Secondary effect measures were incidence rate ratios of AF and 30-day case fatality for stroke patients.

RESULTS

Incidence rates of AF per 1000 person-years in Denmark increased by 5.4% (95% CI 5.3% to 5.7%) for patients aged <65 and 5% (95% CI 4.9% to 5.1%) for patients aged ≥65, whereas the increase was 0.2% (95% CI -0.2% to 0.6%) for patients aged <65 and 2.6% (95% CI 2.4% to 2.8%) for patients aged ≥65 in New Zealand. In Denmark 36 088 subjects were hospitalised with stroke, and 7518 subjects in New Zealand, both showing peaks during winter with peak-to-trough ratios of 1.22 and 1.27, respectively and a decreasing trend. The 30-day case fatality risk for stroke patients having AF is now (2000-2008) about 20% in both countries.

CONCLUSIONS

Although incidence rates of hospitalisation with stroke in patients with AF have decreased in recent years, stroke remains a common AF complication with a high case fatality risk. The marked winter peak in incidence rates of hospitalisation with stroke in AF patients suggests that there are opportunities to reduce this complication. Further studies are necessary to identify how to optimise treatment of AF and prevention of stroke.

Seasonal variations in the onset and healing rates of venous leg ulcers

Objectives

As many vascular pathologies exhibit circannual fluctuation, the aim of this study was to assess the chronobiological features of venous ulcers.

Methods

Based on a retrospective survey of the case histories of 391 venous ulcer patients, the rates of ulcer onset and healing in each month were analysed statistically; a time series was constructed to evaluate the seasonality.

Results

There was a significantly higher frequency of ulcer onset during the warmer part of the year (April–October), and onset showed strong seasonality. Healing rates were also unequally and statistically significantly distributed throughout the year: ulcers that appeared or that were treated with specialized treatment in the winter or summer healed slower in comparison to ulcers that began in the spring or autumn.

Conclusions

Venous ulcers exhibit circannual fluctuations in their onset and healing rates. Hypothetically, in addition to exacerbation of chronic venous insufficiency, seasonal variations in immune system activity might potentially be responsible for this phenomenon.

Circadian Variation in Stroke Onset: Identical Temporal Pattern in Ischemic and Hemorrhagic Events

Stroke is the culmination of a heterogeneous group of cerebrovascular diseases that is manifested as ischemia or hemorrhage of one or more blood vessels of the brain. The occurrence of many acute cardiovascular events--such as myocardial infarction, sudden cardiac death, pulmonary embolism, critical limb ischemia, and aortic aneurysm rupture--exhibits prominent 24 h patterning, with a major morning peak and secondary early evening peak. The incidence of stroke exhibits the same 24 h pattern. Although ischemic and hemorrhagic strokes are different entities and are characterized by different pathophysiological mechanisms, they share an identical double-peak 24 h pattern. A constellation of endogenous circadian rhythms and exogenous cyclic factors are involved. The staging of the circadian rhythms in vascular tone, coagulative balance, and blood pressure plus temporal patterns in posture, physical activity, emotional stress, and medication effects play central and/or triggering roles. Features of the circadian rhythm of blood pressure, in terms of their chronic and acute effects on cerebral vessels, and of coagulation are especially important. Clinical medicine has been most concerned with the prevention of stroke in the morning, when population-based studies show it is of greatest risk during the 24 h; however, improved protection of at-risk patients against stroke in the early evening, the second most vulnerable time of cerebrovascular accidents, has received relatively little attention thus far.

Diurnal Variation of the Incidence of Symptomatic Branch Retinal Vein Occlusion

AIM

To investigate the diurnal variation that is related to the incidence of branch retinal vein occlusion (BRVO).

METHODS

This is a cross-sectional study. 72 consecutive patients who were newly diagnosed with BRVO were precisely questioned about the time of their symptom onset. The clinical history, systemic illnesses, ocular findings, and body mass index were obtained for each patient.

RESULTS

Analysis of the diurnal variation of symptom onset showed a distribution with the peak in the period from 6 a.m. to noon compared with all the other time periods (p < 0.001). Multivariate analysis showed that involvement of the superior retina was the only factor that influenced the onset time of BRVO.

CONCLUSION

Patients with symptomatic BRVO frequently noted their visual deterioration in the morning, which is the same as the other types of ocular and systemic vascular disease. Our results may be helpful for understanding the pathophysiology of BRVO. Our findings require conformation and further studies on this subject are certainly warranted.

Does sleep protect against ischemic stroke? Less frequent ischemic strokes but more severe ones

BACKGROUND AND OBJECTIVE

Stroke occurrence follows a circadian curve, with a higher frequency in the morning. This curve changes if the hours of sleep also change. Our aim was to evaluate the characteristics, risk factors, and prognosis associated with sleep stroke.

METHODS

Patients with ischemic stroke (n = 813), consecutively assessed in our hospital for 2 years, were recorded with the time of clinical onset, pathological antecedents, severity (NIHSS), clinical classification, etiologic TOAST classification, and functional outcome at 3 months (modified Rankin scale). When clinical disturbance appeared during night sleep time it was considered as sleep stroke (SS). The rest were considered wakefulness stroke (WS). Differences SS-WS were analyzed with chi(2), t-student, Mann-Whitney U, and logistic regression tests.

RESULTS

From 813 patients included, 127 were SS (15.6%). The SS frequency was less than expected for the corresponding interval of hours. After the univariate analysis and posterior logistic regression, obesity was a factor associated with SS. Adjustment for age and gender revealed that atrial fibrillation (AF) was less frequent in the SS group. There were no differences for other risk factors or in the etiologic distribution. SS had a greater initial clinical severity and a worse functional outcome at 3 months. This functional outcome was dependent on the initial clinical severity.

CONCLUSIONS

Whilst sleep could be associated with a lesser stroke occurrence, it could also be associated with a higher severity. Obesity appears as a factor related to SS whilst AF appears related to WS.

Seasonal variation in stroke and stroke-associated mortality in patients with a hospital diagnosis of nonvalvular atrial fibrillation or flutter. A population-based study in Denmark

AIM

There are few data on seasonal variation in stroke and seasonal variation in mortality after stroke in patients with atrial fibrillation. We examined the seasonal pattern in stroke occurrence and the effect of the season on mortality after stroke in patients with a history of nonvalvular atrial fibrillation.

METHODS

We identified all individuals, aged 40-89 years, with an incident diagnosis of stroke of any nature (ischemic or hemorrhagic) in the 1980-2002 period and no history of heart valve disease and a previous or concomitant diagnosis of atrial fibrillation or flutter in the Danish National Registry of Patients. Subjects were followed in the Danish Civil Registration System for emigration and vital status. We used periodic regression models to estimate the peak-trough ratio stratified by sex, age and comorbid medical conditions. Seasonal effect on mortality after stroke was analyzed in a Cox proportional hazards model.

RESULTS

The relative incidence of stroke estimated as the ratio of the incidence in the month of the peak (January) to the incidence in the month of the trough (July) was 1.11 (95% confidence interval: 1.07-1.15). The relative incidence of stroke was similar for men and women, did not differ by age (stratified by age 75 years) and was essentially similar for comorbid conditions considered. There was no seasonal effect on mortality after stroke.

CONCLUSIONS

The occurrence of stroke in patients with atrial fibrillation is modestly higher during the winter. Stroke-associated mortality does not vary by season.

The related causes in very early morning onset of stroke

We investigated the influence of early awakening and related factors on onset of cerebrovascular disease (CVD). Totally 1199 stroke patients, in whom the onset time was known, at 3 reference hospitals were included in this study. The effects of demographic, medical, and pathophysiological factors on the circadian pattern of an unselected series of patients with ischemic stroke were analyzed. Nine-hundred seventeen CVD patients with cerebral infarction (CI), 240 patients with intracerebral hemorrhage (CH), and 42 patients with subarachnoid hemorrhage (SAH) were identified. The greatest portion of strokes (32.5%) occurred between 03:00 and 06:00 a.m. Nearly one half of the strokes in this series occurred in the very early- to mid-morning hours. This analysis of strokes provides strong evidence with a higher risk in the early morning hours (03:00 a.m. to 06:00 a.m.), and lower risk during the night time period (21:00 p.m. to midnight). Approximately 1 of every 3 strokes (1 of 3 ischemic strokes, 1 of 6 hemorrhagic strokes, and 1 of 8 subarachnoid hemorrhages) is attributable to the early morning excess. This difference tried to be explained by three ways: cold weather, religious factors, and physiological mechanisms.

Temporal variation of autonomic balance and diseases during circadian, seasonal, reproductive, and lifespan cycles

Many diseases show patterns of temporal variation that remain unexplained. We hypothesize that oscillation of autonomic balance over different time intervals plays a role in these variations. In the Darwinian struggle, organisms must perform various functions related to fitness such as survival, energy acquisition, and reproduction in a prioritized fashion. Autonomic systems enable differential allocation of effort to various functions under different conditions, some of which vary in patterns that are predictable such as circadian, menstrual, seasonal, and life cycles. For many species, daytime functions such as seeking food and avoiding predators are achieved with sympathetic activity while night-time functions such as internal processing are achieved with parasympathetic activity. For organisms that maintain thermal homeostasis year-round, cooler temperature seasons may demand sympathetic bias to drive adaptive thermogenesis. Reproduction may necessitate autonomic shift to sympathetic bias during the luteal phase and pregnancy to modulate immune balance towards a more tolerant Th2 bias. Many diseases including infectious, cardiovascular, inflammatory, pulmonary, metabolic, fertility, oncologic, and neurologic conditions also show variation in prevalence over these cycles. The co-variation of autonomic balance and diseases over time intervals suggests that autonomic balance, by its direct effects as well as its indirect effects through modulation of T helper immune balance, plays an under-recognized role in diseases. The theory is extended to the co-variation of autonomic balance and diseases over the lifespan. Termination of organisms during senescence, achieved by emergence of autonomic imbalance and other systemic dysfunctions, is explored from a Darwinian perspective.