Temperature variability and hospitalization for cardiac arrhythmia in Brazil: A nationwide case-crossover study during 2000–2015

Highlights

• Temperature variability (TV) was associated with hospitalizations for arrhythmia.

• There were no differences in TV effect by region, age or sex on 0–1 days' exposure.

• Women were more affected by prolonged TV exposure.

Abstract

Background

There is growing recognition of a potential role for environmental and climatic factors in influencing cardiovascular risk. It has been speculated that temperature variability (TV) is a risk factor for cardiac arrhythmia but evidence is limited.

Objective

To quantify the geographic and demographic variations in the association between TV and hospitalization for cardiac arrhythmia in Brazil during 2000–2015.

Methods

Data on hospitalization for arrhythmia and weather conditions were collected from 1,814 cities. TV was calculated as the standard deviation of daily maximum and minimum temperatures during exposure days. A time-stratified case-crossover approach was applied to examine the city-specific association between TV and hospitalization for arrhythmia. City-specific estimates were pooled at the national and regional levels using a random-effect meta-analysis. Stratified analyses were conducted by sex, three age-groups (0–64, 65–74 and ≥75 years), and three arrhythmia subtypes (paroxysmal tachycardia, atrial fibrillation and flutter, and other arrhythmias).

Results

There were 447,667 arrhythmia-related hospitalizations during 2000–2015. The odds ratio of hospitalization per 1 °C increase in TV peaked on 0–1 days’ exposure [1.012 (95% confidence interval: 1.010–1.015)]. There were no substantial differences in effect estimates of TV_0-1 by region, age or sex, except for the non-significant association observed in the north. However, women were more affected by prolonged TV exposure than men. For the three arrhythmias subtypes, only paroxysmal tachycardia and other arrhythmias were sensitive to TV. Assuming a causal relationship, 35,813 (95%CI: 18,302−51,665) cases were attributable to TV_0-1 in Brazil during 2000–2015, accounting for 8.0% (95%CI: 4.1–11.5%) of hospitalizations for cardiac arrhythmia.

Conclusions

At a population-level exposure to TV was associated with increased risk of arrhythmia-related hospitalization in Brazil, with the relationship equally distributed across most residents but varied by arrhythmia subtypes. Our findings add to the accumulating evidence-base that climatic factors can influence cardiovascular outcomes in populations.

Introduction

Globally, cardiovascular diseases (CVDs) are the single, largest cause of death in the past quarter of century, causing an estimated 20 million deaths in 2016, with over 80% occurring in lower- and middle-income countries (CRED, 2018). Cardiac arrhythmia is an important risk factor for death from CVDs, especially in the elderly, in whom impaired cardiac function may exacerbate pre-existing abnormalities (Strait and Lakatta, 2012). In the US alone, the prevalence of atrial fibrillation, one of the most common arrhythmic conditions was estimated at 2.7–6.1 million affected individuals in 2010 (Go et al., 2001; IHME, 2017; Miyasaka et al., 2006).

Traditional cardiovascular risk factors such as elevated blood pressure and cigarette smoking are known to be associated with increased risk of arrhythmia (Benjamin et al., 1994; Javaheri et al., 2012). However, there is a growing appreciation of the role that environmental and climatic factors have on human health. Exposure to suboptimal ambient temperature has been observed to increase an individual's susceptibility to an arrhythmic event (Nguyen et al., 2015). Temperature variability (TV), the rapidly heating and cooling of ambient temperature within a few days, is a more common occurrence than extreme weather events such as heat waves and cold spells (Guo et al., 2016). In some populations, TV has been associated with a range of adverse cardiac outcomes such as stroke mortality and hospitalization from heart failure (Lim et al., 2012a; Yang et al., 2013). Whether TV increases the propensity for an arrhythmic event has been less well studied, with the evidence to date inconclusive.

Brazil has a significant burden of CVD morbidity and mortality (IHME, 2017a; b), in part due to its sizeable, aging population combined with its economic development over the past two decades. In this study, we used a Brazilian national dataset spanning 2000–2015 to quantify the geographic and demographic variations in the association between TV and hospitalization for arrhythmia. The heterogeneous variation in Brazil's climatic and geographical zones will enable the most reliable examination to date, of the strength and directionality of the association between TV and risk of hospitalization for arrhythmia at a population-level.