Mam, let's make one thing clear. Who's suffering from ankylosing spondylitis, you or your husband ?
High hemoglobin levels most commonly occur in tobacco smokers. Since your husband hasn't kicked his habit, this may be the cause. Quitting smoking helps but reducing doesn't.
The high hemoglobin levels doesn't mean it's good, infact the hemoglobin in the red blood cells is inefficient to carry oxygen as much as you would like it.
Cigarette smoke carries 4000 different toxic chemicals including tar, carbon monoxide etc. During a drag the temperature at the tip of a cigarette rises to 1200 degree centigrade which is 12 times the temperature of boiling water, when inert substances become toxic too. The smoke also contains radioactive elements. The cigarette tar etc cause COPD lung disease, lung cancer, oral cancer, stomach, pancreatic cancers and heart attacks, especially if the patient is diabetic and cerebral stroke.
Though habits die hard, the power of the human spirit is even harder ! So please tell your husband at least to try to quit smoking absolutely and kick the habit for good.
Another cause of polycythemia or high hemoglobin levels chronically is Polycythemia Rubra Vera, which is a type of blood cancer. You need to consult a hematologist for tests which will exclude this condition.
Next Steps
In all probability your husband is suffering from polycythemia due to tobacco smoking and you need not worry about much except make him quit smoking.
Health Tips
Nowadays, nicotine chewing gums are available which reduces the craving for nicotine during quitting if taken properly.
There are some medicines too which reduces the craving but in both cases you will require a doctor's prescription as they have side effects.
There are many good effects of quitting which starts from less than 5 minutes of giving up smoking and spanning over 20 yrs. You will be astonished.
Sometimes a short counselling and motivation by a doctor is all that is needed to ignite the spark of inspiration to quit.
If the hemoglobin is persistently high, your husband might have to take aspirin, provided he doesn't have any contraindications, that is he is not bleeding from any site, no active peptic ulcers etc. High hemoglobin will increase blood viscosity and make the patient prone to heart attacks, ischemic brain stroke and limb vessel thrombosis. Aspirin being an antiplatelet agent will prevent clotting of blood.
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I also desire to check your husband clinically.
There is a joke : Giving up smoking is very easy, I have done it many times !
Please ensure Mam that this doesn't happen with your husband.