About 1% of the world’s adult population suffers from pulmonary hypertension (PH). Among the many forms of this disease is idiopathic pulmonary arterial hypertension (IPAH), a rare but very severe disease. The term “idiopathic” means that there is no tangible cause for the disease. A study group led by the Department of Pneumology at the Hannover Medical School (MHH) has determined that smoking probably plays a causal role in the development of a particularly severe form of IPAH. The researchers came to this conclusion by analyzing data from two pulmonary hypertension registries. The scientific work was published in the journal The Lancet Respiratory Medicine.