Healthy Aging Among Centenarians and Near-Centenarians: Findings from the Georgia Centenarian Study

Abstract

The Georgia Centenarian Study is one of the earliest comprehensive studies on centenarians. Based on the Georgia model of adaptation, the primary purpose of this study was to assess the health and well-being of our oldest population, with a focus on several primary adaptation areas: genetics and family longevity, environmental support, individual characteristics, cognitive and behavioral skills, health behaviors, and physical and mental health, including overall life satisfaction. The results of the three Georgia Centenarian sub-studies indicate that genetic and environmental variables play an important role in determining different levels of healthy aging, but they also highlight relevant mediating and moderating effects in a network of interrelating adaptation components.

1.0. Introduction

Living a long, satisfactory, and healthy life is a goal most, if not all, adults strive to attain. Demographic trends in all developed countries show that average life spans gradually get longer, and more adults live longer past the century mark [1]. As people live longer, more scientific studies are being conducted to unmask the underlying mechanisms that can contribute to living longer and well --- that is, healthy aging [2].

The goals and central themes of this paper on healthy aging of the oldest old based on findings of the Georgia Centenarian Study (GCS, 1988–2008) are:

1. Healthy aging is a dynamic and ever-changing process that varies according to an individual’s unique characteristics and environment. As different individuals age, this process would vary across an individual’s history and their past and present environment; physical, cognitive, and functional performances; personality, attitudes, perceptions, available resources, and other variables.

2. Future research to further understand healthy aging needs to be cognizant of specific individual and environmental contributions and the direct and indirect (or interactive) influences of these contributions.

The GCS is one of the first population-based studies that examined multiple individual and environmental predictors of healthy aging among centenarians and near-centenarians. One innovation of the study was to understand, compare, and contrast the relative impact of predictors on healthy aging. A second innovation was differentiating different paths to healthy aging among oldest-old adults. Hence, the study aimed to initiate and build a multi- and inter-disciplinary model of healthy aging among community-dwelling individuals and those residing in care facilities who lived to extreme old age.

The GCS consists of three phases of research from 1988–2006 [2]. The National Institute of Mental Health (RO1 MH43435–10) funded the first two phases. Phase 1, 1988–1992, was a cross-sectional study of the Georgia model among community-dwelling 60-year-old (N = 91), 80-year-old (N = 93), and 100+ year old (N = 137) individuals. Phase 2, 1992–1997, was a 5-year longitudinal follow-up study of the same individuals tested in Phase 1. Phase 3, 2001–2006, was a collaborative, multi- and inter-disciplinary population-based study of representative samples of centenarians (N = 244) from the State of Georgia funded by the National Institute on Aging (1 PO1 AG17553–01A1). The Georgia Centenarian Study also includes a considerable number of African Americans. Out of our total sample of centenarians and near centenarians (N=381), 26.0% (N=99) were African Americans, representative of the population in Georgia.

The following are summaries of major findings across the three phases of the GCS associated with each cluster of predictors and outcome variables, as well as an exploration of the interrelationships among predictors on outcomes. Table 1 describes the main domains contributing to longevity and selected results according to the Georgia Centenarians Study.

Table 1.

Domains and Major Findings of the Georgia Centenarian Study

Domains	Major Findings	References
Genetics/Family Longevity	Father’s age at death predicts remaining life expectancy after 100 years	Poon et al., 2000
	HRAS1, LASS1, and APOE are associated with longevity	Jazwinski et al., 2010
	APOE ε4 allele exacerbates the effect of life events on negative affect	Martin et al., 2014
Environmental Support	Centenarians have reduced social support resources	Martin et al., 1996
	Social support is important for physical and mental health	Randall et al., 2011
	Caregivers’ negative perceptions of the centenarians’ well-being status is associated with higher levels of caregiver burden	Lee et al., 2017
	Centenarians who are viewed as agreeable and conscientious are less of a burden to caregivers	Cho et al., 2020
Individual Characteristics	Centenarians show low levels of neuroticism, but relatively high levels of extraversion, competence, and trust	da Rosa et al., 2020
	Centenarians become less sensitive, but more open to experience after 20 months retest	Martin et al., 2002
Cognition	About half of the centenarians have mild to moderate dementia, and a quarter have the most severe level of dementia	Leung et al., 2023
	Educational, occupational responsibility, an engaged lifestyle, social engagement, and high levels of activity (“cognitive reserve”) protect against cognitive decline in very late life	Martin et al., 2023
Nutritional Behavior	Centenarians are likely to eat a regular breakfast, do not engage in weight loss diets, and have no major fluctuations in body weight	Johnson et al., 1992
	Mental health is a highly significant nutritional risk factor for centenarians	Nickols-Richardson et al., 1996
Physical Health and Functional Health	The most common physical health problems include cardiovascular disease (80%), pneumonia (43%), and cancer (30%)	Arnold et al., 2010
	Later-born centenarians had higher levels of physical function when compared to earlier centenarian cohorts	Cho et al., 2012
Mental Health/Life Satisfaction	Functional impairment, neuroticism, and perceived economic status are the strongest predictors of self-rated mental health	MacDonald et al., 2009
	Social resources and neuroticism were the strongest predictors of loneliness.	Margrett et al., 2009
	Negative emotions predict life satisfaction over time, whereas positive emotions are contemporaneously associated with life satisfaction	Bishop et al., 2011

2.0. Method

This review was conducted by the authors of this article as they are the principal and co-principal investigator of the Georgia Centenarian Study. Relevant research studies addressing each of the components (e.g., genes and family longevity, environmental support, etc.) of the Georgia Centenarian Study were selected. The focus was on centenarians alone or in comparison to younger age groups. If publications contained information about indirect effects and about the amount of variance explained, this information was included in this paper.

3.0. Impact of Genes and Family Longevity

Popular views on longevity suggest that long-lived family members are guideposts for the next generation within the family. Individuals look at family longevity when assessing their chances to live a long life. The GCS examined the direct and interactive impact of family longevity and specific genetic contributions on our centenarian sample’s obtained longevity and adaptation.

First, the GCS focused on family longevity and how it might be associated with the continued survivorship of centenarians. Would the longer life span of parents be related to continued survival after age 100? Poon et al. [3] reported that participants in our study survived on average for another 3.2 years. The results indicated that father’s age at death exerted a positive effect on the number of days of survival after 100 years. Mother’s age at death, however, was not directly associated with survival beyond 100 years.

Second, it remains unclear to what extent genetic markers or family lifestyle contribute to longevity. Several genetic markers, such as the protective allele of FOXO3 and variants of the APOE gene (alleles 2 and 4) are associated with longevity [4, 5]. In combination with the Louisiana Centenarian Study [6], data from the GCS reported that three candidate genes (HRAS1, LASS1, and APOE) assessed in the GCS were associated with human longevity and healthy aging.

Finally, less attention has been paid assessing gene-environment interactions. One of our studies investigated the association between the APOE gene, life events, and emotional well-being among centenarians [7]. The gene–environment interaction suggested that carriers of the APOE e4 allele had higher scores of negative affect after having experienced more life events, such as parental divorce, job-related events or financial losses. In contrast, non-carriers had reduced negative affect levels after having experienced more events.

4.0. Impact of Environmental Support

There is no question that genetic and environmental factors play an important role in determining healthy longevity [8]. This section highlights the importance of environmental resources in the form of social and economic support that could impact healthy aging and longevity. Both components of environmental support have implications for caregiving.

In one of our early studies on centenarians [9], we reported that centenarians had a reduced social support network with fewer visits and phone conversations when compared to younger age groups. However, more than 90 percent of the centenarians reported having a confidant. Randall et al. [10] tested a support-efficacy model for centenarians and noted that social relations were important for very old adults’ mental and physical health. Perceived competence (“self-efficacy”) mediated the association between social support and mental health.

Social support for centenarians can be burdensome for the caregivers who quite often are older. Lee et al. [11] reported that caregivers perceived the centenarians’ social and emotional condition more negatively than the centenarians themselves, and the caregivers’ negative perceptions of the centenarians’ well-being status was associated with higher levels of caregiver burden. In a similar study assessing the caregiving of centenarians, Cho et al. [12] reported that centenarians who were viewed as agreeable and conscientious were less of a burden to caregivers, whereas caregivers who perceived centenarians to be relatively high in neuroticism and ill health were more likely to be a burden to caregivers.

Few centenarian studies have highlighted the importance of economic resources among centenarians. One of our first centenarian publications indicated that more than two-thirds of the centenarians in the Georgia study had incomes that placed them under the poverty level [13]. Interestingly, over 95% of centenarians indicated they were financially doing the same or better than others their age. MacDonald et al. [14] investigated distal and proximal factors influencing economic dependency among centenarians and found that reduced cognitive ability had the strongest effect on medical care and caregiving services. Personality factors, such as neuroticism and conscientiousness, had significant effects on total hours of care received, indicating that more neurotic and conscientious centenarians demanded more care. The results suggest that the care needed by centenarians not only affects their health but also the health of care providers.

5.0. Impact of Individual Characteristics – Personality

Popular views on centenarians would suggest that centenarians are “exceptional,” “unique,” and “special.” These views may relate to the personality characteristics of this unusual group of survivors. The GCS employed two personality assessments to identify unique characteristics among community-dwelling centenarians.

Using the 16 PF personality inventory [15], we found that centenarians scored higher on dominance, suspiciousness, and imagination, while scoring lower on emotional stability and conformity [16]. Personality traits, together with coping behaviors and stress, reliably predicted mental health, explaining about one-third of the variance in morale and mental health among the centenarians.

The GCS further identified personality traits using the NEO-PI assessment [17]. We found a centenarian profile characterized by low levels of neuroticism, but relatively high levels of extraversion, competence, and trust. Centenarians’ caregivers or family corroborated this personality profile. In comparing centenarians in the United States and Japan, DaRosa et al. [18] reported that these configurations were similar in the two countries.

Baek et al. [19] assessed the association of two higher personality traits (alpha and beta) with different functioning levels. Alpha personality type pertains to relatively high levels of emotional stability, agreeableness, and conscientiousness. Beta personality type pertains to higher levels of extraversion and openness to experience and was related to higher levels of cognitive functioning, higher likelihood of volunteering, better activities of daily living and higher levels of subjective functioning. Alpha and beta together with demographic characteristics (i.e., age, gender, race/ethnicity, and residence type) explained 33 percent of the variance in cognitive function, 10 percent in volunteering, and 39 percent in activities of daily living. That personality can still change even in very late life was demonstrated by Martin et al. [20], who reported that centenarians became less sensitive, but more open to experience.

6.0. Impact of Cognition

The GCS examined the pattern of distribution of dementia severity among a population-based sample of 244 centenarians. Dementia severity was diagnosed by a seven-point Global Deterioration Scale [GDS, 21]. In stage 1, 6.6% of centenarians had no cognitive decline. In stage 2, 15.9% had memory complaints, but no objective evidence of cognitive decline was found. Stages 3 to 5 could be defined as mild to moderate dementia. About 56% of centenarians had this level of severity. Finally, 22.9% of centenarians had the most severe stages of 6 and 7 in that most cognitive abilities are lost and around-the-clock assistance is needed. The GCS population-based sample showed that about one-quarter of centenarians had no objectively evaluated dementia. About half of the centenarians had mild to moderate dementia, and a quarter had the most severe level of dementia. These rates are similar to other centenarian studies [22].

The GCS examined the reliability and validity of psychometric and biomedical measures of dementia for centenarians, where few measurement studies had been conducted. First, the GDS exhibits a high and significant association with the MMSE and Clinical Dementia Rating, two instruments commonly used in global dementia assessment. Second, for centenarians, there is high concordance between the GDS levels of dementia severity with central executive functioning, word fluency, memory, and abstract reasoning. Third, high concordance was also established between the GDS and physical and instrumental daily living and mobility activities. Fourth, high concordance was also established between GDS and variations in neuropathological findings in Braak score, cerebral atrophy, brain weight, and National Institute on Aging-Reagan Institute criteria for dementia.

Cognitive functioning in very late life is important to maintain high levels of life quality. The GCS noted that individuals build reserves over the life span that predict cognitive function in very late life [23]. Building cognitive reserve starts early in life with educational experiences, and education continues to have a strong, lasting effect on cognitive function in very late life. Furthermore, occupational responsibility, an engaged lifestyle, social engagement, and high levels of activity all build up a reserve that protects against cognitive decline in very late life [24].

7.0. Impact of Nutritional Behavior

Much of the longevity literature has emphasized the importance of health behaviors contributing to an exceptionally long life. The GCS primarily focused on nutritional behaviors. Our early studies indicated that centenarians were likely to eat a regular breakfast, did not engage in weight loss diets, and had no major fluctuations in body weight [25]. Centenarians consumed more vegetables and took nutritional advice from their doctor and family more than relying on news media. Furthermore, centenarians were less likely to follow diets that were low in fat, and they were not particularly likely to comply with nutritional guidelines emphasizing the risk of chronic disease. These findings reflected the nutritional patterns of their cohort rather than their age.

Quinn et al. [26] reported that age, low economic resources, and male gender were risk factors for poor nutritional health-seeking behavior, whereas personality factors of self-discipline, enthusiasm, sensitivity, and warmth were protective factors. Furthermore, Black centenarians were at greater nutritional risk than White centenarians [27].

Nickols-Richardson et al. [28] also assessed predictors of nutritional risk and reported that the number of illnesses and mental health were the most significant predictors of nutritional risk, explaining almost thirty percent of the variance for three age groups in their 60s, 80s, and 100s. For centenarians, somatic aspects of mental health were highly significant nutritional risk factors. The nutritional findings from the GCS indicated that centenarians were not following a specific diet different from other people but that with advanced age, centenarians are more likely to be at nutritional risk.

8.0. Impact of Physical and Functional Health

One of the most visible condition of centenarians is their physical and functional appearance. Centenarians may look frail, have difficulties walking, and may be limited in caring for themselves. The GCS comprehensively assessed physical health and functional capacity.

Arnold et al. [29] noted that four out of ten centenarians had survived a chronic disease before age 80, and only 17 percent had “escaped” a chronic disease altogether. Very few centenarians have therefore lived their lives without chronic diseases. The most common physical health problems included cardiovascular disease (80%), pneumonia (43%), and cancer (30%).

Another important marker of physical health is the subjective rating of one’s health. Our findings on subjective health indicate relatively high self-rated health levels among centenarians, with more than 70 percent evaluating their health as “good” or “excellent.” Poon et al. [30] noted that functional capacity, mental health, and the personality trait “conscientiousness” were significantly associated with better subjective health, explaining 39 percent of the variance. In an alternative model, mental health and social support were also associated with subjective health, explaining more than 35 percent of the variance in subjective health.

The second health component covered in the literature on centenarians includes functional health, or activities of daily living (ADL). Our early studies indicated highly significant differences in all ADL tasks when this age group was compared to octogenarians and sexagenarians. Only about 20 percent of these highly functioning centenarians could shop without help or engage in housework, and only about 12 percent could go places by themselves.

Martin et al. [31] assessed correlates of functional capacity among centenarians. Their results suggest that centenarians at a younger age and those living in the community-rated their functional health as better when compared to centenarians who were older and lived in care facilities. Additional positive correlates with functional capacity included positive affect, conscientiousness, social support, religious coping, and an engaged lifestyle. The final model explained more than 33 percent of the variance in functional capacity. Finally, there are positive trends when comparing different cohorts of centenarians. Cho et al. [32] compared more recent Georgia centenarians to earlier centenarian cohorts and noted that later-born centenarians had higher levels of physical function when compared to earlier cohorts.

9.0. Impact of Mental Health and Life Satisfaction

Even though physical health and functioning are important parts of exceptional longevity, equal emphasis should be placed on mental health and life satisfaction. The GCS has placed a primary focus on psychological well-being. MacDonald et al. [33] used an overall self-rated mental health measure and found that functional impairment, neuroticism, and perceived economic status were the strongest predictors of self-rated mental health, explaining about 30 percent of the variance. Temple-Scheetz et al. [34] pointed out that there are no age differences comparing centenarians to two other older age groups in the dysphoria depression dimension. Johnson-Nicholson [35] evaluated a structural model predicting depressive symptoms for African American centenarians and reported that social resources were associated with lower depressive symptoms.

Cho et al. [36] compared centenarians’ positive emotions with a group of octogenarians and noted that centenarians with higher cognitive and physical function levels also showed higher levels of positive affect. Evaluating positive and negative affect over 20 months, Poon et al. [37] noted a significant decline in positive but not negative emotions.

Cho et al. [38] reported significant effects of perceived physical health impairment and social resources on positive subjective well-being. The results suggest important pathways from individual characteristics (e.g., education), cognitive, physical, and functional health to psychological well-being. Altogether, the variables in the model predicted more than 50 percent of the variance in positive affect. Cho et al. [39] evaluated a physical health model predicting positive and negative affect in another study. The results suggested that subjective health mediates the effect of physical and biological markers on both positive and negative affect.

The GCS team also assessed levels of loneliness among centenarians. Martin et al. [40] indicated that about one-third of centenarians were lonely sometimes or often. Anxiety, low levels of social support, and physical health problems were associated with loneliness. Margrett et al. [41] evaluated predictors of loneliness among centenarians, and social resources and neuroticism were the strongest predictors of loneliness.

Bishop et al. [42] evaluated predictors of life satisfaction cross-sectionally and longitudinally among centenarians. The results suggest that negative emotions predict life satisfaction over time, whereas positive emotions are contemporaneously associated with life satisfaction. Positive and negative emotions are important mediators when assessing the relationship between cognitive skills and life satisfaction. Bishop et al. [43] reported that negative emotions mediated the association between perceived health, functional health, and fatigue, with life satisfaction as the outcome.

10.0. Summary and Conclusions

The concept of healthy aging among the oldest-old population has been studied in other centenarian studies [4, 44, 45, 46] but needs to be re-defined. Some have advocated that there is no healthy aging among centenarians [44], as many of these survivors appear to be frail. The counterargument is that centenarians have outlived the general adult population by some 30 years. They must possess unique characteristics and/or lifestyle practices that could contribute to their exceptional survival. The goal of the GCS was to identify and validate these characteristics on the one hand and to highlight individual differences in their pathways toward longevity on the other hand.

What have we learned about healthy aging of the oldest old?

One, data collected from the GCS showed that public health recommendations for healthy living apply to the oldest-old population. Although centenarians and near-centenarians are generally frailer than their younger cohorts, family longevity, physical/functional/cognitive health, health practices/behavioral/coping skills, and supportive resources are significant predictors of life satisfaction and mental health.

Two, the GCS data showed that healthy aging among oldest-old adults is a process in that different individuals may travel different paths toward healthy aging and longevity. Some may have exceptional genetic predispositions to influence healthy aging outcomes. Some may have exceptional cognition, physical health, or strong support resources. Different individuals can take different paths, and we can examine how these paths could impact different outcomes. The GCS defined life satisfaction and mental health as outcomes. Future studies could examine other outcomes that may be congruent with their research questions.

Three, although frailty is common among oldest-old adults, the GCS data show centenarians develop compensatory behavioral and coping skills and personality traits that support their life satisfaction and mental health. Healthy aging is in the eye of the beholder, where positive attitudes and survival traits are found among the frail.

Four, estimates of dementia prevalence among centenarians are subject to the composition and makeup of the sample. Small and convenience samples would likely provide inaccurate estimates. This may be the primary reason that different studies report different prevalence.

Five, based on a population-based sample, the GCS data showed that 25% of the centenarians were cognitively intact, 50% had mild and moderate levels of dementia, and 25% had severe and greatly debilitating dementia. It is important to recognize that poor hearing and poor vision are prevalent in centenarians and can lead to inaccurate estimates of dementia. Studies vary in how dementia is assessed and this can lead to an underestimate of dementia.

Six, the GCS can be viewed as a pioneering study that has pointed the way in future studies of healthy aging and the oldest-old population. Future studies would be well served to employ multi- or inter-disciplinary predictors of individual differences in predisposed factors such as genetic contributions and current and distal history and environment. Future studies should examine not only direct and indirect or interactive effects to get a complete picture of variances accounted for. Finally, care needs to be exercised to include the influences of culture within the population. After all, the GCS found individual differences in healthy aging are both objective and subjective.

Highlights.

• The Georgia Centenarian Study is one of the first comprehensive centenarian studies providing information about healthy longevity.

• Family longevity and environmental support play an important role in determining different levels of healthy aging.

• Personality, cognition, and psychological well-being are essential components of healthy living among centenarians.

Data sharing and collaboration

There are no linked research data sets for this paper. Data sharing can be arranged by investigators getting in touch with the principal investigator.