Cough can be produced due to may reasons like lung disorders (asthma
, interstitial lung disease, tuberculosis
etc)；upper airway disorders；GERD etc.
Your wife is suffering from cough for last 1 year and it episodic so asthma came first to my mind but it may be due to upper airway cogh syndrome or GERD.
can tell whether your wife has asthma or not.
You should consult a pulmonologist
for the diagnosis and management of your wifes cough.