Cardiovascular diseases morbidity and mortality are increasing over time, - decompensated HF being one of these diseases - and constituted a burden for countries health systems, especially in sub Saharan Africa. Identification of factors contributing to this burden help to understand their pathophysiology, and to find right solution. Climate and meteorological parameters have been suggested as factors that affect admissions and mortality related to CVDs. We found that admission rates and mortality indicators were higher during long raining seasons (where humidity level is higher, and temperature is lower) and were inversely correlated to temperature.
Admission for decompensated HF represented 36.2% of total admissions during our study period; more than half of deaths in the cardiology unit were related to decompensated HF. Boombhi et al. observed a similar result in the same unit few years ago, with admissions rate of 30% and 33.3% respectively in 2014 and 2015 . These high admission rates can be explained by the increasing rate of cardiovascular risk factors -among these risk factors are hypertension, obesity, smoking- in sub Saharan Africa; knowing that HF is one of the most common outcome of these risk factors . Furthermore, there is a low treatment awareness, medical adherence and disease control for these CVDs. Medication nonadherence and uncontrolled hypertension were among the three most frequent precipitating factors for decompensated HF in our study. Therefore, more sensibilization is needed to reduce the burden of cardiovascular risk factors and thus HF burden. Mortality rate was lower in a group of patients admitted in US for HF between 2011 and 2013 – the overall mortality rate there was 3.1% . This suggest that sub-Saharan Africa health systems need more resources and capacity building to decrease HF mortality.
Admission, mortality and lethality rates were inversely correlated to the monthly mean temperature, and they seem higher during the long rainy season. This result is consistent with the result of Ansa et al., who observed a higher admission rate of heart failure during the rainy season . Similar results were also observed in the north hemisphere, where higher rates of heart failure admissions were obtained during the winter – a season where temperature are lower and humidity is higher compare with other seasons . The main explanation of this higher admission rate seems to be related to lower temperatures in these seasons, through various mechanism. Exposition to cold increases the sympathetic and renin – angiotensin - aldosterone systems activities, leading to higher heart rate, peripherical vascular resistance and blood pressure. This exposition also decreases vasodilator effect of azote monoxide. All these effects increase heart post charge and reduce the cardiac output, resulting in higher probability of decompensation of pre-existing HF. Patient’s education must therefore emphasize on the need of more attention to the respect of therapeutic recommendations during cold periods like rainy seasons. Health workers and stakeholders must also be aware of this increase of needs in cardiology unit during rainy seasons.
The higher mortality rate observed during the rainy season may also be explained by external factors to the patient like the availability of heath human resources in hospitals during rainy seasons, especially in low and middle incomes countries like Cameroon. Most of the health worker in our context doesn’t own a private car which can permit them to get at work on time when there is rain. The health care workforce availability may thus be reduced during rainy seasons, leading to higher mortality rates as it have been showed in other context .
Our study may have underestimated the real burden of decompensated HF, as it was a hospital-based study. In our country, patients recourse to other therapeutic means like traditional healer, prayers and self-medication. Another limit is that autopsy wasn’t perform for death patient, and they may be other death causes for our patient that HF.