Coronary stenosis as a modifier of the effect of cold spells on the risk of sudden cardiac death: a case-crossover study in Finland

Seasonal variation of unexpected sudden cardiac death in northern Finland

BACKGROUND

Data on the occurrence of unexpected sudden cardiac death (SCD) in different seasons are limited.

METHODS

All unexpected sudden death victims have to undergo medico-legal autopsy obligated by the Finnish law. Consecutive series of all unexpected autopsied SCD victims (n = 5,869) were prospectively collected from the geographically defined area in the Northern Finland during a twenty years period from 1998 to 2017. We evaluated the seasonal variation of SCD and its possible causes.

RESULTS

Unexpected SCD occurred more frequently during the first quarter of a year (from January to March) than during the other quarters. The occurrence of SCD during the twenty years follow-up was 4.5 ± 0.24 during the first quarter of the year per month and 3.9 ± 0.12 during the other quarters of the year per month on average (SCDs during the quarter of a year per month on average per 100,000 inhabitants per year, p < 0.001). The weather was colder during the first quarter of the year (average temperature -9.1 degrees centigrade) than during the other quarters (average temperature +5.7 degrees centigrade). The subjects who experienced SCD during the first quarter of the year had more commonly severe (75 %-90 %) coronary artery stenosis, (p < 0.001).

CONCLUSION

Unexpected SCD occurred more commonly during the first quarter of a year (from January to March) than during the other quarters (from April to December). Cold weather with its physiological consequences and more severe coronary artery disease predisposing to ischemia may have contributed to the increased occurrence of SCD during the first quarter of the year.

Short-term exposures to temperature and risk of sudden cardiac death in women: A case-crossover analysis in the Nurses' Health Study

Background

Sudden cardiac death (SCD) is a major source of mortality and is the first manifestation of heart disease for most cases. Thus, there is a definite need to identify risk factors for SCD that can be modified on the population level. Short-term exposures to temperature have been implicated as a potential risk factor. Our objective was to determine if short-term temperature exposures were associated with increased risk of SCD in a US-based time-stratified case-crossover study.

Methods

A total of 465 cases of SCD were identified among participants of the prospective Nurses' Health Study (NHS). Control days were selected from all other matching days of the week within the same month as the case day. Average ambient temperature on the current day (Lag0) and preceding 27 days (Lags1-27) was determined at the residence level using 800-m resolution estimates. Conditional logistic distributed lag nonlinear models (DLNMs) were used to assess the relative risk (RR) of the full range of temperature exposures over the lag period.

Results

Warmer exposures in the days before event and colder temperatures 21-28 days prior were associated with increased risks of SCD. These results were driven by associations in regions other than the Northeast and among married women.

Conclusions

Both warm and cold ambient temperatures are suggestively associated with risks of SCD among middle-aged and older women living across the United States.

Associations between cold spells of different time types and coronary heart disease severity

Limited evidence showed the association between cold spells and the severity of coronary heart disease (CHD). This study was to investigate the association between cold spells with their different time types and CHD severity. We collected data on CHD patients admitted to the Zhongnan Hospital, Wuhan, China from 2016 to 2021. CHD severity was quantified using the SYNTAX score and transformed into a binomial variable. Daily mean, maximum and minimum temperature were collected during the study period. We first used daily mean temperature to find the optimum definition among multiple thresholds and durations. The daily maximum and minimum temperatures were used to define different types of cold spells (daytime, nighttime and compound) based on the optimum definition. Annual cold spell days were included to assess individual exposure to cold spells. Logistic regression models were performed to fit the association between cold spell days and CHD severity stratified by different tertiles of PM2.5 and NDVI. In this study, 1937 CHD patients were included. The cold spell defined as at least four consecutive days with daily mean temperature below the 5th percentile exhibited the optimum model. We found that a 4-day increase in cold spell days was associated with more severe CHD (OR = 1.170, 95% CI: 1.074, 1.282). Such an association was more pronounced under higher levels of PM2.5 by OR = 1.270 (1.086, 1.494) and lower levels of greenness by OR = 1.240 (1.044, 1.476). Compared with daytime and compound cold spells, nighttime cold spells showed the strongest association with CHD severity by OR = 1.141 (1.026, 1.269). This study showed that exposure to cold spells was positively associated with CHD severity, especially the nighttime cold spells. The association between cold spells and CHD severity was more significant in high levels of PM2.5 and low levels of greenness.

Effects of Cold Spells on Mortality - Ningbo City, Zhejiang Province, China, 2014-2018

What is already known about this topic?

In recent years, climate change may lead to an increase in cold spells in the middle latitudes, and there is a positive correlation between cold spells and population mortality.

What is added by this report?

The acute response period and the vulnerable population were identified under the optimal definition of cold spells, and the mortality burden caused by cold spells was estimated.

What are the implications for public health practice?

This research would provide evidence on the acute mortality effects of cold spells in southern China. Therefore, vulnerable populations, especially the elderly, should take timely measures to reduce the health damage caused by cold spells, especially in the first week after cold waves.