Epidemiology of Longevity: What Contributes to a Longer Life?
- Fay
- 3 hours ago
- 5 min read
Overview of longevity
Over the past century, human longevity has risen so sharply that it is sometimes described as an “epidemic.” While there is no universal definition, age 85 is often used as the threshold for advanced age. With improvements in public health and medical care, the number of people living past 90—and especially centenarians—has grown rapidly. U.S. Census data show that the 90+ population is the fastest-growing subgroup among those over 65. For example, fewer than 3% of individuals born in 1910 reached age 90, whereas projections suggest that up to 20% of women and 15% of men born in 2000 will do so.
Despite this trend, the maximum human lifespan has increased only marginally. Hundreds of people have reached 110, but those approaching 120 remain exceedingly rare, fueling debate over whether human longevity has a fixed upper limit. Statistically, the chance of surviving from birth to 90 is about the same as from 90 to 100, highlighting why centenarians make valuable study populations: rare enough to be unique, yet numerous enough to provide meaningful insights.
The primary driver of increased longevity has been environmental improvements—advances in sanitation, nutrition, education, housing, and healthcare that reduced early deaths from infections, malnutrition, and accidents. In the latter half of the 20th century, better prevention and treatment of chronic disease extended survival further. Yet modern health threats such as obesity may slow or even reverse these gains in younger generations.
Among the ultra-elderly, disease onset and functional decline are often delayed. Research shows that about one-third of centenarians, more than half of semi-supercentenarians (ages 105–109), and nearly 70% of supercentenarians (ages 110–119) avoid major illnesses like dementia. Roughly half of centenarians remain free of serious health problems until after age 80. While women are more likely to reach extreme old age, men often exhibit better physical and cognitive function at those ages. These findings suggest that exceptional longevity may arise from a combination of unique genetic factors and distinctive ways of adapting to the environment.
What Contributes to a Longer Life
Behavior and cardiovascular risk and longevity
Numerous studies have shown that cardiovascular risk factors are strongly associated with longevity and healthy ageing. Although the definition of “excellent survival” varies from study to study, heart disease, cancer, stroke, and chronic obstructive pulmonary disease are generally recognized as the most important influences. The association between these diseases and longevity is further supported by the life histories of centenarians.
Epidemiologic follow-up studies consistently show that people who maintain low levels of blood pressure and cholesterol and do not smoke tend to have lower mortality rates and longer life expectancies. For example, the Multiple Risk Factor Intervention Trial found that people at low risk lived 6-10 years longer. The Nurses' Health Study and the Framingham Heart Study also confirmed that ideal cardiovascular status in midlife significantly increased the probability of survival to age 85 and healthy survival to age 85; conversely, more risk factors were associated with lower survival rates.
Overall, this prospective evidence suggests that maintaining a healthy lifestyle and controlling cardiovascular risk in adulthood is critical to achieving longevity and delaying functional decline. These behavioral and environmental factors simultaneously provide important clues for exploring the role of gene-behavior and gene-environment interactions in longevity.
Reproductive phenotypes and longevity
The female longevity advantage has been observed as early as the late 19th century. Men generally have a higher mortality rate from conception through the life cycle, while women have a better survival rate than men at all ages. This advantage is almost universal, except in a few societies where women are disadvantaged by cultural factors or the HIV/AIDS epidemic. In individual longevity groups, such as in Sardinia, male longevity is comparable to that of females, suggesting that there may be as yet unspecified environmental or genetic factors.
Evolutionary theory suggests that there is a trade-off between reproductive capacity and longevity. Studies have found that centenarian women tend to be more likely to give birth at an advanced age than women who die prematurely, and that later childbearing is strongly correlated with longer life expectancy. Historical demographic data also show that later childbearing age is associated not only with increased life expectancy for women themselves, but also with increased life expectancy for their male relatives. This phenomenon supports the hypothesis that “later childbearing may share a genetic basis with slower ageing”.
Genetic factors and longevity
Genes play a key role in longevity. Genome-Wide Association Studies have shown that the single nucleotide polymorphism rs2075650, located in the TOMM40 gene, is associated with longevity in 90-year-olds, and that harboring this variant reduces the probability of surviving to 90 years of age by nearly 30%. This finding is consistent with the role of the APOE ɛ4 allele, which has been repeatedly validated in several candidate gene studies and in centenarian populations.
In addition to APOE, other longevity-related genes are involved in lipid metabolism, DNA repair, and RNA regulation. For example, specific variants in the CETP gene were associated with larger HDL/LDL particle sizes and lower risk of hypertension and cardiovascular disease in a German-Jewish longevity study. A further GWAS meta-analysis found that several loci associated with susceptibility to age-related diseases were enriched in longevity populations, including the 9p21 chromosome region, which is associated with atherosclerosis, diabetes, and cancer risk.
These findings are highly consistent with experimental models: longevity is often associated with downregulation of growth and metabolic signaling. For example, mutations in the insulin signaling pathway extend lifespan from yeast to mammals; caloric restriction also acts by reducing growth factor signaling. This is further supported by epidemiologic evidence, such as the pattern of disease mortality and longevity in Okinawan populations that maintain a low-calorie diet and low body mass index over time, which is consistent with experimental results. However, it is worth noting that not all long-lived individuals rely on caloric restriction, and some ultra-elderly populations have even mildly overweight ranges of body mass index, suggesting that complex interactions between genetics and the environment still need to be explored in depth.
Conclusion
Epidemiologic studies of longevity are important for understanding the mechanisms of aging and guiding public health interventions. The aging process is closely linked to lifelong behaviors, and interventions that target known risk factors are expected to consistently improve life expectancy and healthy longevity. Longevity is both genetically influenced and plastic. Genetic and animal model studies have revealed several key pathways that reduce the risk of chronic disease in later life and extend disease-free survival and disability-free survival. These findings are expected to be translated into effective strategies to reduce morbidity in old age, improve physical and cognitive functioning, and enable the ultimate goal of longevity research - a healthy and high-quality extension of life.
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