Association between stroke occurrence and changes in atmospheric circulation

The short-term effect of weather variables on heart rate variability in patients after open-heart surgery

The aim of the study was to detect the associations between heart rate variability (HRV) and weather variables in patients who underwent coronary artery bypass grafting or valve surgery. The study was performed in Kaunas, Lithuania, during 2008-2012. We used data of 220 patients. HRV was assessed by a 5-minute electrocardiogram. The data were collected at 1.5 months, 1 year, and 2 years after the surgery (495 measurements). A negative association of standard deviation of beat-to-beat interval (SDNN), very low frequency (VLF), low frequency, and high frequency (HF) powers with a decrease in air temperature (T) during a 3-day period in the range of T < 1°C wind speed >2.75 knots 2 days before, and the daily North Atlantic Oscillation indices were observed. The effect of wind speed on SDNN and VLF power was stronger in males. Two days after relative humidity >89%, a lower mean VLF and higher HF in normalized units were found; in females, this effect was stronger 1.5 months after the surgery. Among patients after open-heart surgery, the HRV variables may be related to specific weather changes and the effect of weather was different for males and females and at different times after the surgery.

Risk of ischemic and hemorrhagic stroke in relation to cold spells in four seasons

BACKGROUND

Cold winter weather increases the risk of stroke, but the evidence is scarce on whether the risk increases during season-specific cold weather in the other seasons. The objective of our study was to test the hypothesis of an association between personal cold spells and different types of stroke in the season-specific context, and to formally assess effect modification by age and sex.

METHODS

We conducted a case-crossover study of all 5396 confirmed 25-64 years old cases with stroke in the city of Kaunas, Lithuania, 2000-2015. We assigned to each case a one-week hazard period and 15 reference periods of the same calendar days of other study years. A personal cold day was defined for each case with a mean temperature below the fifth percentile of the frequency distribution of daily mean temperatures of the hazard and reference periods. Conditional logistic regression was applied to estimate odds ratios (OR) and 95% confidence intervals (95% CI) representing associations between time- and place-specific cold weather and stroke.

RESULTS

There were positive associations between cold weather and stroke in Kaunas, with each additional cold day during the week before the stroke increases the risk by 3% (OR 1.03; 95% CI 1.00-1.07). The association was present for ischemic stroke (OR 1.05; 95% CI 1.01-1.09) but not hemorrhagic stroke (OR 0.98; 95% CI 0.91-1.06). In the summer, the risk of stroke increased by 8% (OR 1.08; 95% CI 1.00-1.16) per each additional cold day during the hazard period. Age and sex did not modify the effect.

CONCLUSIONS

Our findings show that personal cold spells increase the risk of stroke, and this pertains to ischemic stroke specifically. Most importantly, cold weather in the summer season may be a previously unrecognized determinant of stroke.

Association between Outdoor Air Pollution and Fatal Acute Myocardial Infarction in Lithuania between 2006 and 2015: A Time Series Design

BACKGROUND

Air pollution has a significant effect on human health and there is a broad body of evidence showing that exposure to air pollution is associated with an increased risk of adverse health effects. The main objective of this study was to assess the association of traffic-related air pollutants with fatal AMI during the ten-year period.

METHODS

The study was conducted in Kaunas city, where the WHO MONICA register included a total of 2273 adult cases of fatal AMI cases during the 10-year study period. We focused on the period between 2006 and 2015. The associations between exposure to traffic-related air pollution and the risk of fatal AMI were evaluated by using a multivariate Poisson regression model, RR presented per an increase in IQR.

RESULTS

It was found that the risk of fatal AMI was significantly higher in all subjects (RR 1.06; 95% CI 1.00-1.12) and women (RR 1.12; 95% CI 1.02-1.22) when the concentration of PM₁₀ in the ambient air was increased 5-11 days before the onset of AMI, adjusting for NO₂ concentration. The effect was stronger during spring in all subjects (RR 1.12; 95% CI 1.03-1.22), in men (RR 1.13; 95% CI 1.01-1.26), in younger-aged (RR 1.15; 95% CI 1.03-1.28), and in winter in women (RR 1.24; 95% CI 1.03-1.50).

CONCLUSIONS

Our findings show that ambient air pollution increases the risk of fatal AMI, and this pertains to PM₁₀ specifically.

Effects of Changes in Seasonal Weather Patterns on the Subjective Well-Being in Patients with CAD Enrolled in Cardiac Rehabilitation

Objective: We examined whether seasonal and monthly variations exist in the subjective well-being of weather-sensitive patients with coronary artery disease (CAD) during cardiac rehabilitation. Methods: In this cross-sectional study, 865 patients (30% female, age 60 ± 9) were recruited within 2−3 weeks of treatment for acute coronary syndrome and during cardiac rehabilitation. The patients completed the Palanga self-assessment diary for weather sensitivity (PSAD-WS) daily, for an average of 15.5 days. PSAD-WS is an 11-item (general) three-factor (psychological, cardiac, and physical symptoms) questionnaire used to assess weather sensitivity in CAD patients. Weather data were recorded using the weather station “Vantage Pro2 Plus”. Continuous data were recorded eight times each day for the weather parameters and the averages of the data were linked to the respondents’ same-day diary results. Results: Weather-sensitive (WS) patients were found to be more sensitive to seasonal changes than patients who were not WS, and they were more likely to experience psychological symptoms. August (summer), December (winter), and March (spring) had the highest numbers of cardiac symptoms (all p < 0.001). In summary, peaks of symptoms appeared more frequently during the transition from one season to the next. Conclusion: This study extends the knowledge about the impact of atmospheric variables on the general well-being of weather-sensitive CAD patients during cardiac rehabilitation.

Association between El Niño-Southern Oscillation events and stroke: a case-crossover study in Kaunas city, Lithuania, 2000-2015

The aim of this study was to determine the association between the daily number of cases of ischemic stroke (IS) and hemorrhagic stroke (HS) in patients aged 25-64 years and the El Niño-Southern Oscillation (ENSO) events during 2000-2015. As an indicator of the effect of the ENSO, the monthly NIÑO 3.4 index (Equatorial Pacific Sea Surface Temperature) was used. During the 5844-day study period, 5600 cases of stroke (3170 (56.61%) in men and 2430 (43.39%) in women) were analyzed. Of these, 4354 (77.8%) cases were IS, and 1041 (18.6%) cases were HS. In 3496 (62.2%) cases, stroke occurred in the age group of 55-64 years. In the analysis, we used the following categories of the ENSO events: strong La Niña, moderate La Niña, moderate El Niño, and strong El Niño. The effect of the ENSO was examined by using the multivariate Poisson regression adjusting for weather variables. The highest risk of both strokes (BS) was observed on days of strong and moderate La Niña (rate ratio (RR) 1.27, 95% CI 1.13-1.42) and RR = 1.15 (1.07-1.23), respectively), while the risk for IS was the highest on days of moderate El Niño (RR = 1.11(1.02-1.20)). A lower risk for BS was found on days of strong El Niño (RR = 0.77(0.62-0.97)). We found that ENSO events affected the occurrence of BS and IS in all age groups, and the strongest effect was observed among females. The results of this study provide new evidence that ENSO events may affect the risk of stroke, especially the risk of IS.