The evidence to date strongly suggests that environmental factors determine longevity for the vast majority of people. If there are significant longevity-affecting gene variants out there, then they have small and unreliable effects (APOE), or are restricted to tiny lineages (SERPINE1), or both.
The overwhelming majority of contributions to longevity emerge from lifestyle choices relating to weight, exercise, smoking, and so forth, and exposure to persistent pathogens such as cytomegalovirus. In the near future we'll add access to rejuvenation therapies to this list, but that is only just getting underway now and isn't yet relevant to epidemiological studies of older people.
Elderly couple. Image credit: Bridget Coila via Flickr, CC BY-SA 2.0
Today's open access paper on environment and lifestyle choice versus the odds of becoming a centenarian is interesting for showing a few correlations that stand in opposition to the rest of the literature. For example, lower educational achievement and being widowed correlates with greater odds of living to 100 in this study.
This is perhaps a good example of the perils of epidemiology, and particularly the challenges inherent in reasoning about epidemiological data. One should never take any one paper at face value without considering the rest of the literature, and one should bear in mind that different views (just people in one geographic area) or slices of data (just older people) may well produce opposing results.
The survival probability of becoming a centenarian has been shown to be multifactorial. The rapid increase in the odds of living to 100 years of age is largely due to substantial advancements in medicine and public health that decreased the burden of disease. Genetic factors, including genes in several pathways influencing longevity, such as inflammation and immunity, have also been explored. These studies have shown that longevity is likely to be a polygenic trait, but aging has been attributed to be only 20-35% heritable. Social and environmental factors, such as high educational attainment and socioeconomic status, also significantly contribute to longevity.
This study aimed to examine the likelihood of becoming a centenarian for adults aged 75 and above in Washington State and to identify social and environmental correlates of healthy aging and longevity. In addition, we identified geographic clusters within Washington State where individuals are more likely to become centenarians. Models were adjusted for sex, race, education, marital status, and neighborhood level social and environmental variables at the block group level. In the adjusted model, increased neighborhood walkability, lower education level, higher socioeconomic status, and a higher percent of working age population were positively associated with reaching centenarian age. Being widowed, divorced/separated, or never married were also positively correlated compared to being married. Additionally, being white or female were positively correlated with reaching centenarian status.
Surprisingly, education was found to be negatively associated with becoming a centenarian. In recent studies, higher education levels have been strongly associated with lower mortality. Higher academic level indicates employment opportunities and lifestyles associated with factors such as socioeconomic status, social connections, availability and knowledge of health resources, health behaviors (e.g., not smoking), and critical thinking skills applied to managing health problems.
Rapid advances in educational attainment in the last few generations may explain, in part, the lack of a positive association between educational attainment and becoming a centenarian in our study. In this regard, in 1950, only 34.3% of the U.S. population above the age of 25 had a high school diploma, a figure that increased to more than 80% by 2000. More recent studies have demonstrated increasing declines in mortality with education, suggesting that education is less of a factor in determining longevity in older populations.
Another unexpected finding was that compared to married older adults, those who never married, or were widowed, or divorced/separated were more likely to become centenarians. Being widowed showed the greatest benefit, with never having married coming second, and being divorced/separated showing the least benefit. Decades of work have consistently observed that marriage is associated with longer survival than being divorced or never having married. However, this study specifically focused on those aged 75 and above, so the selection aspect and some of the protective factors may not be as relevant.
Many studies have not explored the effects of marital status on health at older ages specifically. In this study, the finding of a much greater likelihood of becoming a centenarian for those who are widowed may be partially explained by the fact that those who lost their spouses earlier in life may no longer experience the stresses associated with the traumatic event. This line of reasoning may also contribute to the findings around being divorced/separated leading to a greater likelihood of becoming a centenarian, which is not generally consistent with prior research.
Source: Fight Aging!