Key points from article :
Two thirds of older men suffer from hypertension.
Some men do not respond to common drug treatments the therapy.
If lifestyle changes also haven't helped, may be due to underlying cause.
Other cuases include kidney disease, Cushing's disease, pheochromocytoma and sleep apnea.
The studies were published in the Journal of Clinical Sleep Medicine, BMC Cardiovascular Disorders and in The Journal of Clinical Hypertension.