Running Head : EXCEPTIONAL LONGEVITY

Exceptional Longevity : An Overview of Centenarian’s Environmental, Psychological, Social and Genetic Backgrounds

Tahmina Sarwari University of Toronto at Scarborough November 2nd, 2010

Over the last few centuries, the life expectancy of humans has significantly increased; a trend that is expected to continually grow at a rate of 2.5 years per decade (Arnold et al., 2010). As such, humans nowadays can expect to live longer than their ancestors before them. Several studies have aimed to determine what factors contribute to exceptionally prolonged existence. The following text shall explore the genetic, environmental, psychological as well as lifestyle factors common in centenarians, a population believed to be exemplary of optimal functioning in humans, to determine norms that can explain this phenomenon, shedding light on the gateways to prolonged life. Finally, the text shall address the implications of these research findings.

One breakthrough study, known as the “Georgia Centenarian Study” by Poon and colleagues conducted in 1992, has been exceptional in sparking subsequent research in the field of gerontology. This study consisted of recruiting 285 centenarians and individuals nearing 100 years of age (i.e. 98 years and older) from a 44-county area of northern Georgia (Davey et al., 2010). Participants were recruited from skilled nursing facilities, personal care homes as well as located through voter registry. Numerous subsequent studies have used the population-based data obtained from this study for further analysis of factors contributing to increased longevity.

One such study by Martin et al. (2009), entitled “Engaged Lifestyle, Personality and Mental Status among Centenarians” aimed to provide empirical evidence for the commonly accepted hypothesis that a positive mindset and engaged personality have beneficial health outcomes. The measures they focused on were Engaged Lifestyle, Personality as well as Mental Status. The ‘engaged lifestyle’ component was determined in terms of level of education and by several cognitive engagement tasks. For the education variable, participants were divided into two categories; 1) low level of education, where achievement only up to completion of high school occurred and 2) high level of education, namely attainment of post-secondary education.

Cognitive tasks were evaluated based on a self-report questionnaire, including questions such as “Did he/she typically prepare his/her own taxes”; “Did he/she typically balance his/her own check book”; “Did he/she ever travel to a foreign country?” (Martin et al., 2009). Personality traits such as extraversion, neuroticism, conscientiousness, openness and agreeableness were assessed by using the NEO Personality Inventory (NEO PI-R), where 240 items were presented to each participant who were asked to rate themselves on a 5-point scale. Lastly, mental status, or cognitive capacity was measured by using the MMSE (mini-mental state exam). A cut-off score of 18 was determined to differentiate between participants showing signs of severe cognitive impairment (below 18 points) or mild/no cognitive impairment (score equal to or greater than 18).

Martin et al. found that centenarians were high in positive personality traits of Extraversion, Conscientiousness and Agreeableness and low in Neuroticism and Openness. When compared to cognitive mental status, differences were found in personality, where centenarians with high cognitive functioning were more likely to be extraverted, conscientious and open to experience and less likely to be neurotic. Agreeableness however did not show any differentiation (Martin et al., 2009). In contrast, centenarians that belonged to the poor cognitive functioning group did not show a strong relationship between openness and extraversion (Martin et al. 2009). Poon et al. have also aimed to investigate psychosocial determinants of longevity in centenarians. Drawing from population-data obtained from the Georgia Centenarian Study, one measure they found particularly of importance was subjective health, that is centenarian’s perception of their own health. A majority of centenarians rated themselves as healthy, with 19.4% reporting feeling that they are in excellent health and 52.7% rating feeling in good health. Perception of health was found to be positively correlated with functional health ( r =.32) and a negative correlation ( r = -.19) was associated with self-reported health problems (Poon et al., 2010). The more participants reported health problems such as chest pains, arthritis and numbness, the more they were dependent on others for normal daily activities like eating, getting dressed, bathing and taking a walk (Poon et al., 2010).

Poon et al. found several psychosocial predictors that potentially impact longevity as these are determinants of physical and mental wellbeing in later life. One of these are life events, both current – referred to as proximal influences – and historical – referred to as proximal influences (Poon et al, 2010). In the Georgia Centenarian Study, major life events such as marriage, birth of a child, loss of a spouse, child or sibling, health crises, retirement, historical events, institutionalization and strained relationship with child were assessed. They found that distal influences greatly impacted the health of centenarians from the study in that more positive events yielded better self-rated health. A significant 10% of the variance in current health could be accounted for by historical events, outlining the importance of historical events on health.

Further findings were that the number of children was positively correlated with centenarian’s ability to take on activities of daily living (Poon et al., 2010) and a negative correlation with loneliness. That is the more children one had, the more physically able they were and the less lonely they felt. Other distal variables such as childhood health also predicted current health: the greater the number of negative lifetime events reported, the more current health problems reported. This finding has also been reported by Hensley and colleagues. Hensley and colleagues focussed on the impact of family history on functional (taking part in activities of daily living) and mental health, while taking into account factors such as childhood health, economic status while growing up, number of children and living with grandparents before age of 17 (Hensley et al., 2010). Results indicated that a significant predictor of both being able to engage in activities of daily living and loneliness in later life was number of children.

Another predictor Poon et al. assessed was personality type of centenarians. The first Georgia Centenarian study indicated that centenarians were high in dominance, suspiciousness and shrewdness but were low in imagination and tension (Poon et al., 2010). These same participants were retested after 20 months. When comparing initial scores with later ones, it was found that centenarians had lower scores in sensitivity but showed higher scores in radicalism (Poon et al., 2010). Researchers such as Martin posited that the ‘robust personality’ common in centenarians could be an indicator of a ‘survivorship’ resource that helps them adapt to challenges of everyday life (Poon et al., 2010). Much like Martin et al., Poon and his colleagues have found that a unique combination of robust personality traits were common in centenarians, namely, low levels of neuroticism, high extraversion, conscientiousness and agreeableness. Further analyses of these findings indicated that 3 of the 5 personality components predicted mental and physical health. Centenarians who reported being high in conscientiousness were in better physical state but had lower scores in mental health; those high in neuroticism were lower in both mental and physical health whereas individuals high in openness rated higher on both physical and mental health (Poon et al, 2010).

A third psychosocial variable believed to affect longevity is social and economic resource adequacy (Poon et al. 2010). This is based on resource availability and sufficiency in both economical and social terms: that is monetary funds as well as support from family and friends.

Social resource adequacy can be measured by centenarians’ residential setting, for instance, living with family; in private homes; in skilled nursing facilities; nursing home or retirement homes (Poon et al., 2010). The number of hours of care and attention given to them by workers and other caregivers is positively related to the physical and mental well being (Poon et al., 2010). Further, as age increased, centenarians reported feeling a decline in social resources available to them (Poon et al., 2010). Martin found that both types of resources along with life events and childhood socioeconomic status had a positive correlation with mental health: the lower the perceived social and economic resources, the poorer the mental and physical health of the centenarian (Poon et al, 2010). Negative distal life events decreased social resources and self-rated economic status.

Bishop and his colleagues have observed similar findings as those reported by Poon and colleagues. In wanting to assess the state of happiness in centenarians, Bishop and al. took into consideration factors that affect happiness, particularly perceptions of available resources and comparison between past and present circumstances, including life events. They administered self-report questionnaires rating happiness (i.e.: “I am just as happy as when I was younger”); state of health (i.e.: “How would you rate your overall health at the present time?” and “how much do health problems stand in the way of doing the things you want to do?” on a 5-point scale); social provisions (“there is no one I can turn to for guidance”); economic security (i.e.: “Are your assets and financial resources sufficient to meet emergencies?”); and life satisfaction/congruence (i.e.: “As I look back on my life, I am fairly well satisfied”).

Congruence or life satisfaction showed a positive relationship with perceived economic status, perceived health and with current happiness (Poon et al., 2010). That is to say that individuals that reported greater satisfaction with life events also reported feeling healthier, happier and more financially secure. Further, the perception of having greater economic resources also served as a predictor of subjective health. Notably, 44% of the variance in self-reported health status was explained by life satisfaction, financial stability and social resources (Poon et al., 2010).

Another factor thought to greatly influence longevity are environmental factors. Magnolfi and colleagues took on the task of determining whether different environmental settings nurture increased longevity in humans by analysing population data of 287 municipalities in Tuscany, Italy. In doing so, they found that the region of Tuscany inhabited much more centenarians and other elderly individuals than the rest of Italy. This was explained by the flux of emigration and immigration over time (Magnolfi et al., 2010). They found that residents of rural areas tend to reach 90 years of age, whereas habitants of urban areas more frequently attain 100 years of age. This finding initially appears counter-intuitive as urban areas are more crowded and have more environmental pollution than rural areas. However, it can be accounted for the fact that larger cities offer better medical services, are more technologically advanced and economic resources are less sparse (Magnolfi et al., 2010).

Let us now consider another facet of interest to gerontologists; genetic contributions to exceptional longevity. By conducting a genome-wide association study (GWAS) of centenarians, Sebastiani et al. (2010) set to determine whether genetic predispositions can affect longevity, that is whether genes are passed down from generation to generation favouring prolonged life. Their sample consisted of 801 unrelated participants taking part in the New England Centenarian Study (NECS) and 926 related individuals to serve as the control group. Roughly one third of the participants from the NECS sample had an immediate family member reaching exceptional longevity. The control group comprised of 243 NECS participants who were married to centenarian offspring or to people who’s parents passed away at a mean age of roughly 73, as well as 683 individuals from a genome-wide study of single nucleotide polymorphisms (SNP) selected from the Illumina control database (Sebastiani et al., 2010). The Illumina controls were specifically selected by use of an algorithm to ensure that they had similar genetic background as the NECS participants. To increase the validity of their findings, they replicated their study on 254 North American individuals enrolled by Elixir pharmaceuticals ranging from 90 to 114 in age that were unrelated to the NECS participants, and 341 referent participants leftover from the Illumina controls (Sebastiani et al., 2010). Using the data collected from all participants, Sebastiani et al. accumulated a comprehensive model of 150 SNPs which accurately predicted occurrence of exceptional longevity by 77%. Further in-silico analysis, that is analysis via computer simulation, gave way to 19 clusters of categories of varying predictive value that centenarians can be grouped into based on diverse SNP genotype combinations (Sebastiani et al., 2010), or genotypic signatures. Paola et al. then explored whether a relationship could be observed between the different genetic signatures of exceptional longevity and the onset of diseases related to age such as dementia, hypertension and cardio-vascular problems. They did indeed find that participants in different clusters presented onset of symptoms of certain diseases at later stages in life than others which indicated that genetic factors can indeed account for exceptional longevity in humans (Sebastiani et al., 2010).

Davey et al.’s research focused on comparing demographic variables including gender, race (Caucasian or African American), residence (living in community), skilled nursing facility or personal care home and education level with cognitive functioning, physical performance health habits as well as prevalence of disease. (Davey et al., 2010). Cognitive functioning was determined by a variety of tests, including the Mini-mental State Examination (MMSE), Global Deterioration Rating Scale (GDRS), Severe Impairment Battery (SIB), Fulb Object Memory Evaluation (FOME), Wechsler Adult Intelligence Scale (WAIS), Similarities subtest, Finger Tapping, Behavioural Dyscontrol Scale (BDS), Independent Living Scale (ILS), Health and Safety Scale as well as Controlled Oral Word Association Test (Davey et al., 2010).

Physical performance on the other hand were measured using strength of grip for each hand by use of the Jamar hand grip dynamometer as well as knew extensor strength through a manual muscle manometer (Davey et al., 2010). Participants were also subjected to the NIA Short Physical Performance battery to assess physical functional capacity as well as to the Direct Assessment of Functional Status to measure basic and fundamental activities of daily living.

Risky health behaviours were assessed by administering the Mini Nutritional Assessment to determine nutritional status and food intake. Factors such as weight and height were taken into consideration to assess body mass index in order to determine which weight category centenarians belonged to, i.e: underweight, normal weight, overweight and obese (Davey et al., 2010).

Finally, prevalence of disease throughout the course of centenarian’s lives were assessed by conducting physical exams including questionnaires related to various health conditions, both mental and physical.

In terms of gender differences, men showed better on measures of cognitive state and nutrition. Performance on physical tasks were also better in men even though men reported a higher incidence of smoking and alcohol use both current and in their lifetime. Women on the other hand presented greater prevalence of health problems, particularly depression and osteoporosis, whereas men were more prone to neurological problems (Davey et al., 2010).

In terms of race, Caucasion centenarians performed better than African Americans in cognitive and physical tasks indicating better cognitive functioning as well as better physical performance where grip strength is concerned. The two also differed in lifestyle choices: more African Americans reported smoking habits throughout lifetime and higher nutritional intake, with more African American’s rated as overweight or obese, having diabetes, hypertension and stroke, whereas Caucasian’s were more prone to developing osteoporosis (Davey et al.).

When comparing the health of centenarians living in the community with their families with those living in nursing homes, it was found that a community environment was more conducive to higher cognitive functioning. Residents of the former outperformed those of the latter on physical tasks. In terms of lifestyle choices and health, more members living in community reported current alcohol use whereas facility residents reported more former alcohol use. Finally, facility residents were more prone to mental illnesses such as depression; osteoporosis and heart failure. As per Hensley and colleagues, this finding can be explained by a lack of happiness and feelings of loneliness in centenarians living in nursing homes as they are not surrounded by family members.

To conclude, the myriad of studies on commonalities observed in centenarians provide indicators contributing to exceptional longevity in humans. Research on SNPs have shown genetic components to optimal aging; gender studies have further supported a genetic basis to prolonged life. Studies on residential status as well as psychosocial and environmental factors surrounding individuals have all shown that prolonged life in humans cannot be attributed to a single factor but that a holistic approach is necessary in understanding the mechanisms conducive to it. In sum, these findings suggest that we can increase the number of years we live by making better lifestyle choices, as these choices of our past serve as strong determinants of our future mental, physical and overall health.
References
Arnold, J., Dai, J., Nahapetyan, L., Arte, A., Johnson, M. A., Hausman, D., et al. (2010). Predicting Successful Aging n a Population-Based Sample of Georgia Centenarians. Current Gerontology and Geriatrics Research, PMC2946582
Bishop, A. J., Martin, P., MacDonald, M., Poon, L., Jazwinski, S. M., Green, R. C., et al. (2010). Predicting Happiness Among Centenarians. Gerontology, 56(1), 88-92.
Davey, A., Elias, M. F., Siegler, I. C., Lele, U., Martin, P., Johnson, M. A., et al. (2010). Cognitive Function, Physical Performance, Health, and Disease: Norms from the Georgia Centenarian Study. Experimental Aging Research, (4), 394-425.
Hensley, B., Martin, P., MacDonald, M., Poon, L., Jazwinski, S. M., Green, R. C., et al. (2010). Family History and Adaptation Among Centenarians and Octogenarians. Gerontology, 56(1), 83-87.
Magnolfi, S. U., Noferi, I., Petruzzi, E., Pinzani, P., Malentacchi, F., Pazzagli, M., et al. (2009). Centenarians in Tuscany: The Role of the Environmental Factors. Archives of Gerontology and Geriatrics, 48(2), 263-266.
Martin, P., Baenziger, J., MacDonald, M., Siegler, I. C., & Poon, L. W. (2009). Engaged Lifestyle, Personality, and Mental Status Among Centenarians. Journal of Adult Development, 16(4), 199-208.
Poon, L. W., Martin, P., Bishop, A., Cho, J., da Rosa, G., Deshpande, N., et al. (2010). Understanding Centenarians' Psychosocial Dynamics and their Contributions to Health and Quality of Life. Current Gerontology and Geriatrics Research,