Genome survey for loci that influence successful aging: results at 10-cM resolution

Cognitively elite, cognitively normal, and cognitively impaired aging: neurocognitive status and stability moderate memory performance

OBJECTIVE

Although recent theories of brain and cognitive aging distinguish between normal, exceptional, and impaired groups, further empirical evidence is required. We adapted and applied standard procedures for classifying groups of cognitively impaired (CI) and cognitively normal (CN) older adults to a third classification: cognitively healthy, exceptional, or elite (CE) aging. We then examined concurrent and two-wave longitudinal performance on composite variables of episodic, semantic, and working memory.

METHOD

We began with a two-wave source sample from the Victoria Longitudinal Study (VLS; source n = 570; baseline age = 53-90 years). The goals were to: (a) apply standard and objective classification procedures to discriminate three cognitive status groups, (b) conduct baseline comparisons of memory performance, (c) develop two-wave status stability and change subgroups, and (d) compare of stability subgroup differences in memory performance and change.

RESULTS

As expected, the CE group performed best on all three memory composites. Similarly, expected status stability effects were observed: (a) stable CE and CN groups performed memory tasks better than their unstable counterparts, and (b) the stable (and chronic) CI group performed worse than its unstable (variable) counterpart. These stability group differences were maintained over two waves.

CONCLUSION

New data validate the expectations that (a) objective clinical classification procedures for cognitive impairment can be adapted for detecting cognitively advantaged older adults, and (b) performance in three memory systems is predictably related to the tripartite classification.

Successful cognitive aging

Given the rapid rate of population aging, basic science and public health efforts have increasingly focused on the determinants of successful cognitive aging. In this chapter, we review the definition and biological, psychological, and environmental determinants of cognitive health in later life. Successful cognitive aging is a multi-dimensional construct that lacks a consensus operationalized definition, and has been variously conceptualized in an ipsative, normative, or criterion-referenced manner. Nevertheless, there are a number of biomarkers, at the genetic and cellular level, that provide indicators of cognitive health in aging. Functional and structural neuroimaging suggest multiple pathways to successful cognitive aging, by way of brain reserve and cognitive reserve. A number of behavioral and environmental interventions, including dietary restriction, physical activity, and cognitive stimulation, are promising avenues for extending the cognitive healthspan associated with normal aging. Thus, there is a variety of recent findings providing optimism that successful cognitive aging, howsoever defined, will be attainable by more older adults in the future.

A genome screen of successful aging without cognitive decline identifies LRP1B by haplotype analysis

Successful aging without cognitive decline (SA) is apparent in those who escape age-related illnesses, such as cardiovascular disease and dementia. To determine whether there are protective genotypes that increase the probability of successful cognitive aging, a genome-wide screen was conducted on subjects who were 85 years of older, had MMSE scores >26, and had no major illnesses. SNP 500K microarrays were used. The data from the microarrays was analyzed versus that from Alzheimer's patients. Three SNPs in the gene for the low density lipoprotein receptor-related protein 1B (LRP1B) had significant P values, after Bonferroni correction. Additional SNPs were analyzed in this very large gene. Haplotypes in intron 18 were significant for successful aging versus Alzheimer's patients; those haplotypes were not significant when Alzheimer's patients versus CEPH controls were analyzed. These results suggest that haplotypes in the gene LRP1B are significant/protective for successful aging without cognitive decline.

Successful aging: from phenotype to genotype

Despite worldwide interest in the increasing human "healthspan," inadequate experimental attention has been dedicated to identifying genetic influences on successful aging beyond those that influence longevity alone. Although it is an under-studied topic, some promising leads have emerged from the existing genetic studies of successful aging. Here we describe the results of a systematic review of published family, twin, linkage, and association studies of successful aging that evaluated at least one other characteristic of healthy aging in addition to longevity. We identified 29 studies that met our criteria. Although methodological inconsistencies in sampling and phenotypes were frequent, we found evidence for a substantial genetic contribution to successful aging, including several specific genes (APOE, GSTT1, IL6, IL10, PON1, and SIRT3) that are promising candidates for future molecular genetic research. In addition to reviewing this literature, we provide recommendations for advancing our understanding of the genetic basis of successful aging.

Reduced Age-Related Cataracts Among Elderly Persons Who Reach Age 90 With Preserved Cognition: A Biomarker of Successful Aging?

Tissue damage due to oxidative stress has been implicated in aging, memory loss, and cataract formation. We hypothesized that persons who achieved exceptional longevity with preserved cognition (successful aging [SAG]) would exhibit a lower rate of age-related cataract (ARC) than the general population. The age-specific rates of ARC for a group of 100 (50 male, 50 female) elderly persons who reached at least age 90 years with preserved cognition were compared to the corresponding rates of ARC reported in five population-based studies. The principal finding of this report was that the SAG group manifested a significant reduction in the age-specific rate and lifetime cumulative incidence of ARC compared to the general population. Steroid use, alcohol consumption, gout, and skin lesions resulting from excessive sun exposure emerged as risk factors. Our findings suggest that the progressive development of lens opacities may be reflective of degenerative events occurring more generally throughout the body.

Recent advances in research on successful or healthy aging

This article reports a selective review of biopsychosocial research on successful or healthy aging published in 2005 and 2006. We describe a number of studies that advance the understanding of the definitions, predictors, mechanisms, and potential interventions for successful aging. Successful aging is a multidimensional construct that awaits a standardized definition. A broad array of phenotypes beyond longevity has been examined, including neurocognition, subjective quality of life, and biological age. Considerable progress has been made toward understanding possible mechanisms of successful aging through translational research. Interventions to augment healthy lifestyles have great potential to enhance global healthy aging.