Would a person with frequent sinus and upper respiratory problems have a greater chance of getting cancer or any other more serious conditions?
It depends, why does the person have sinusitis? Why do they have respiratory problems? If they have the above illnesses and if they are only due to say allergies or a deviated nasal septum for example, then no, they are not more susceptible to cancer.
If, on the other hand, these respiratory and sinus problems are because they are being exposed to a carcinogen (something known to cause cancer), then yes, they are more prone to contracting all forms of cancers. Cigarette smoking is a good example. Repeated irritation to the tissues may cause pharyngitis and the like but also the exposure to the carcinogens in the smoke predispose them to cancers. It should be noted that all individuals who smoke, do not get cancer. Additionally, some people that have never smoked, do indeed get many forms of cancer.
Not necessarily. I have not seen any evidence or studies to suggest a specific link between respiratory issues of an infectious nature and cancer, but it is certainly possible. there is a lot about the causes of cancer we do not yet understand.
Sinusitis is more common in smokers, and smoking certainly raises the risk of a number of cancers, including esophogeal and lung, but in that case the smoke and not the sinus issues would be the chief cancer causing agent.
As far as other serious conditions, it depends on what the other respiratory problems are. Allergic reactions can be very serious, of course, and dealing with a series of infections over time leads to some antibiotics not being effective any longer, and can lead to sleep and energy issues.