Effect of environment and season on acute decompensated heart failure: Data from low-to middle-income country

Abstract

Objectives: The environmental effect in heart failure (HF) patients is well established. However, the data is limited from low-to middle-income countries like India. This study determined the impact of environment on acute decompensated HF (ADHF) admissions and mortality in India.

Methods: Retrospectively, the data of all HF patients admitted between April 2017 and March 2019 was accessed through electronic hospital records. Simultaneously, the environmental-related data was collected from the central pollution control board.

Results: The study included 4561 patients of ADHF. The peak of monthly ADHF events (admission and mortality) was observed during the chilly month (January) while the lowest rates were observed in summer months (May-June). The most significant factor correlating inversely with the monthly ADHF admission (r = -0.78, p = 0.003) and mortality (r = -0.65, p = 0.004) was the maximum air temperature, and it was found to be the independent predictor for both ADHF mortality [t = -2.78, β = -0.84; 95%CI(-6.0 to -0.6), p = 0.021] and admission [t = -4.83, β = -0.91; 95%CI(-19.8 to -6.9), p = 0.001]. The above correlation was better seen in the elderly subset and male gender. Humidity and the air pollution attributes did not have a significant correlation with ADHF admission or mortality.

Conclusion: In conclusion, even in low-to middle-income country like India, a periodic effect of season was demonstrated for ADHF mortality and admission, with a peak in ADHF events noted during winter months especially in the regions having extremes of seasons. Air pollution could not affect the ADHF outcome for which further studies are needed.

Keywords: Air pollution; Heart failure; Season.

Fig. 1

The study design flow chart. HF: heart failure, LVEF: left ventricular ejection fraction.

Fig. 2

Seasonal trend of monthly HF admissions. HF: heart failure, group I: heart failure with reduced ejection fraction, group II: heart failure with borderline/preserved ejection fraction. Parenthesis showing mean ± standard error of mean in each sub group.

Fig. 3

Comparative cyclical trends of monthly HF admissions and maximum air temperature (panel A), and monthly HF mortality and maximum air temperature (panel B). HF: heart failure. X axis represents the time axis (in months). Primary Y-axis represents monthly HF admissions (panel A) and monthly HF mortality (panel B), and the secondary Y-axis represents the maximum air temperature (in ⁰Celsius).

Fig. 4

Seasonal trends of monthly HF admissions according to age groups, gender and urban/rural stay (panel A & B) and monthly HF mortality according to age group and gender (panel C & D).

Supplementary Fig. 1

Scatter diagram showing significant inverse correlation between HF admission and maximum air temperature (in ⁰Celsius). HF: heart failure, group I: heart failure with reduced ejection fraction, group II: heart failure with borderline/ preserved ejection fraction.