Dr Haji told the BBC she attributed the rise in SCD deaths to three factors.

BBC: Bahrain sickle cell death rise causes concern

Severe SCD episodes, regardless of how they are triggered, need to be dealt with quickly.

BBC: Bahrain sickle cell death rise causes concern

Smoking duration was also significant, resulting in an 8% increase in SCD risk for every 5 years of smoking.

FORBES: No Surprise: Smoking and Sudden Cardiac Death Closely Tied

In an exploratory analysis, women smokers with coronary heart disease (CHD) had a much higher incidence of SCD than women without CHD.

FORBES: No Surprise: Smoking and Sudden Cardiac Death Closely Tied

Women with CHD who quit smoking did not enjoy the same immediate reduction in SCD risk as observed in women without CHD.

FORBES: No Surprise: Smoking and Sudden Cardiac Death Closely Tied

However without definitive proof, questions remain and Dr Haji acknowledges there is a lack of proper research into CS gas use and SCD deaths.

BBC: Bahrain sickle cell death rise causes concern

Compared to women who never smoked, the risk of SCD was significantly elevated in current smokers (relative risk 2.44) and former smokers (RR 1.40).

FORBES: No Surprise: Smoking and Sudden Cardiac Death Closely Tied

Questions asked by the BBC about what research, if any, has been conducted at Salmaniya on the effects of teargas on SCD sufferers have not been answered by the hospital.

BBC: Bahrain sickle cell death rise causes concern

The number of cigarettes smoked each day was correlated with the increase in SCD risk, but even women who smoked only 1-14 cigarettes per day had a significant 1.84-fold increase in risk.

FORBES: No Surprise: Smoking and Sudden Cardiac Death Closely Tied

Women who quit smoking reduced their SCD risk.

FORBES: No Surprise: Smoking and Sudden Cardiac Death Closely Tied