Aging causes disease. To many people, the relationship is even closer: aging is a disease. The latter view is controversial. Most biologists and physicians would view aging as a “natural process” and contend that “normal aging” is independent of disease. Aging, in this view is not a disease, although it certainly causes disease. They often […]
3.0 Aging Disease
Aging causes disease.
To many people, the relationship is even closer: aging is a disease. The latter view is controversial. Most biologists and physicians would view aging as a “natural process” and contend that “normal aging” is independent of disease. Aging, in this view is not a disease, although it certainly causes disease. They often distinguish between, for example, “normal” brain aging and abnormal brain aging, such as Alzheimer’s, Parkinson’s, Frontotemporal dementia, vascular dementia, and other dementias.
The academic position that “aging is not a disease” is understandable, but ironically inconsistent with normal human behavior. The same academics who argue that “aging is not a disease” are seen to dye their gray hair, undergo Botox treatments or plastic surgery for wrinkles, buy “anti-aging” skin creams, and do everything they can to avoid aging… Judging from behavior (as opposed to academic argument), humans act as though aging were a disease. We go to a great deal of trouble to avoid a “natural process”. So is aging a disease? There is no objective answer. We argue that aging is not a disease, while acting as though it is.
Nor does the argument that “aging is a natural process” validate the position. Aging may be quite natural, but we avidly avoid many “natural processes” because of the risk of death, pain, disability, or fear. Labor pains and neonatal mortality, infections and epidemics, starvation and malnutrition, broken bones and head injuries, and almost everything that modern medicine works to prevent, cure, or treat is a natural process. Simply because a process is natural does not mean that we accept, condone, or value the outcome of such natural processes. Polio infection, smallpox, and tetanus are all natural processes, but these are also diseases, diseases that we put a lot of global effort into eradicating or preventing.
To argue that infection, trauma, genetic disease, or cancer are natural processes is rational, but misses the point and merely results in clinical nonsense. Yes, these are all natural, but are they desirable? No. Precisely the same can be said of both aging and age-related diseases. Natural yes, desirable no.
Arguments about whether or not aging is a disease lose contact with our daily reality. Rather than dispute semantics consider the practical questions: can we do anything about aging and age-related diseases? Most people find both aging and age-related disease to be uncomfortable and worth avoiding – if possible. One of my 94 year-old patients was asked if she would take a pill to reverse aging. “No, I’d rather let nature take it’s course”. I asked about the scar on her sternum: “Quadruple bypass surgery.” I inquired about her swollen knuckles: “Arthritis and ibuprofen isn’t helping any more.” Why had she come to the hospital? “I have pneumonia and I need to be admitted to the… Oh, wait, I see what you’re driving at. I’d take the pill!” In the abstract aging is fine, but the reality becomes a different matter.
If we are to intervene in age-related disease, we need to intervene in the aging process itself. Beneath every age-related disease lies a more fundamental “disease”, that of aging. It is the very genetic and cellular processes that we have addressed in our previous blog posts that trigger age-related diseases, regardless of cell-type, tissue, or organ. Whether we are looking at dementia, arterial disease, joint changes, or weakening bone, in every case we can trace the clinical disease to the changes occurring deep within cells. The gradual changes in epigenetic pattern and the consequent changes in cell functions underlie all age-related problems.
The underlying, common problem in age-related disease is the shortening of telomeres with consequent gradual, but pervasive changes in the pattern of gene expression. These epigenetic changes are reflected in a significant degradation of cell function, particularly in the rate of turnover of molecular pools (internally and externally), the slowing of DNA repair, the decrease in mitochondrial efficiency, and the increase in the rate of molecular damage. In addition, cell aging impinges upon the function of neighboring cells in each tissue, even if such neighboring cells are not as far along on the cell aging spectrum. Although the underlying problem is the same (telomere shortening, epigenetic changes, cell dysfunction), the outcome varies between tissues. In the brain, the aging of glial cells results in neuronal dysfunction and is expressed clinically as one of several dementias. In the case of vascular endothelial cells, the outcome is arteriosclerotic pathology, and is expressed as myocardial infarction, stroke, aneurysm, peripheral vascular disease, heart failure, and other syndromes. In joints, we see osteoarthritis. In bone, we see osteoporosis. No organ is spared. Skin, lungs, kidneys, the immune system, the endocrine organs – all tissues and organs demonstrate age-related changes, loss of function, and diseases peculiar to themselves. In every case, however, age-related diseases, regardless of cell type, tissue, or organ, share the same etiology: cell senescence orchestrated by shifts in telomere length. In the next several posts, we will explore the diseases of aging, then move on to interventions to prevent and cure the diseases of aging.