I have completed an updated overview of research on health and longevity. I based this research on the concept that it is not only necessary to maintain health but also longevity and personal growth for a happy life.
I will start with genes because there is a prevailing incorrect belief that genes control our aging, weight, disease, and are blamed for almost everything else.
Broer, Buchaman, Deelen, et al., (2014), a consortium for Genome-Wide Association studies (GWAS) concluded that there are two established genes associated with longevity, APOE and FOXO3. Other genes factor in a number of other functions that they could not reveal with standard genome-wide genotyping and imputation of common variants. CADM2 and GRIK2 did not show consistent associations, but these genes are interesting candidates for longevity. They are involved in Insulin-like Growth Factor IGF-1 pathways, neurons, and cell longevity. Other mechanisms include stress resistance mediated by heat shock proteins, cellular senescence mediated by telomere length, and inflammation/immune function. It is clear that regulation of immunity and cellular senescence influences the human health-span and are particularly associated with disease of aging (e.g., cancer, atherosclerosis, type 2 diabetes, glaucoma). Geneticists generally agree that the genetic contribution to longevity in humans is between 15 and 25 percent. Huge samples are required to identify less significant phenotypes with protective properties and they make it more challenging due to its interaction with a number of age-related diseases, that is, cancer, cardiovascular disease, and dementia, all of which have independent genetic risk variants. However, age related diseases do not strongly relate to longevity, they effect quality of life. Longevity is rare in the general population but becomes common in long-lived families >89 years. This could be associated with rare variants, joint genetic effects (epistasis), but more likely influenced by environmental traditions and epigenetic modifications. Rare variant association analysis using sequencing technology using large samples could help to clarify the partership between nature and nurture (Broer, et al., 2014).
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