Due to the difference in the metabolism and susceptibility of hosts, respiratory diseases can be caused by one or many agents (occupational and environmental agents diet, air-pollutants, toxic aerosols, microbes). Identifying these causes can be difficult due the manifestation period of the symptoms. It was reported that genetics also play a critical role in the origin and development of respiratory diseases. Due to these reasons, chronic respiratory diseases can be the result of the combination of several factors.

Cancer includes a group of diseases that are characterized by an abnormal growth of any kind of cell that divides in an uncontrollable way and has the ability to infiltrate and destroy normal body tissue. Indeed, a single cancerous cell surrounded by healthy tissue will replicate at a higher rate than other cells. This will render the nutrient supply and elimination of metabolic waste products critical. Once a tumor mass has formed, the healthy tissue will not be able to compete with the cancer cells for the inadequate supply of nutrients from the blood stream. Healthy cells will be displaced by tumor cells until the tumor reaches a diffusion-limited maximal size. Therefore, the tumor cells will continue dividing because they do so without regard to nutrient supply.

Cardiovascular diseases (CVD) are diseases of the heart and the blood vessels. It is known that cardiovascular diseases are multifactorial. The risk factors are high blood pressure, smoking, high blood cholesterol level, diabetes, depression and family history. High blood low-density lipoprotein cholesterol levels are strongly associated with the risk of coronary heart disease but weakly with the risk of stroke. The coronary heart and cerebrovascular diseases are the CVD that cause the most death in adults worldwide.

Current concepts of neurodegenerative diseases began to develop over a century ago. A direct correspondence between the formation of the neuropathological lesions and the degenerative process has emerged for many years. Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and sclerosis, are characterized by the progressive loss of specific neuronal cell populations and are associated with protein aggregates. A common feature of these diseases is the extensive evidence of oxidative stress, which can be responsible for the dysfunction or neuronal death.