I've been having a running discussion with an old colleague over the designation: "Diseases of Aging." It would seem that the literature on the subject categorizes any disease that occurs exclusively or preferentially in the older population as a disease of aging. This, to me, is very very wrong. It is a mistake that has actually impeded much scientific advancement in the field of aging research; and it should be corrected.
The group of diseases that happen to occur in older individuals contain biologically unrelated diseases, many of which have nothing to do with the aging process. Furthermore, some of the most important intrinsic diseases of the aging process occur in children, and would not be included in listings of diseases that occur in the elderly.
I would divide age-related diseases into three biological categories:
1) Non-aging diseases that happen to occur in older people. These would include diseases that begin in youth, but which take many years to fully develop; hence occurring disproportionately in an older population. This category of disease would include most of the common types of cancers (e.g., squamous carcinoma of skin, lung cancer, colon cancer, prostate cancer). There is abundant evidence based on epidemiology and pathology evaluations, that these diseases begin to develop in young individuals, but become clinically manifest in older individuals.
2) Diseases that result from the normal aging process. These are common diseases that occur mostly in tissues that stop dividing after a certain age. Osteoarthritis is a good example. As chondrocytes (cartilage cells) stop dividing (a biological feature of aging), worn chondrocytes are no longer replaced by new cells, resulting in progressive damage to joint cartilage, leading to osteoarthritis in the elderly.
3) Intrinsic diseases of the aging process. These are the inherited progerias (discussed in detail in my book, Rare Diseases and Orphan Drugs: Keys to Understanding and Treating the Common Diseases). These diseases are exceedingly rare and occur in infancy and childhood.
Until we stop lumping biologically unrelated diseases of the elderly into the "diseases of aging" category, it is unlikely that we will make much progress in aging research.
Rare Disease Day is coming up February 29 (a rare day for rare diseases). In honor of the upcoming event, I'll be posting blogs all month, related to the rare diseases and to rare disease funding.
- Jules Berman (copyrighted material)
key words: rare disease, orphan drugs, orphan diseases, zebra diseases, rare disease day, disease complexity, common diseases, aging, ageing, diseases of aging, meaning of aging, jules j berman
