zed in only 122 centenarians, who formed the basis for the present study.

genous TNF-a is neurotoxic (based largely on acute inter- ventions) or neuroprotective (based largely on studies on genetically modified animals) during inflammatory proc- esses in the CNS10 (e.g., functional outcomes in TNF-a knockout mice were improved earlier after brain injury than in wild-type mice, but TNF-a knockout mice showed permanent deficits and reduced recovery).11

Dementia

The diagnosis of dementia was made according to the World Health Organization criteria from the International Classification of Diseases, as previously described.2 Details are given in Appendix 1. Briefly, the Mini-Mental State Examination (MMSE) was used for screening of cognitive function. Actual living conditions and the need for assist- ance from other people were recorded using combined in- formation from the centenarian and caregivers/proxies. Activities of daily living (ADLs) were measured using the Katz Index and Lawton instrumental ADL (IADL) scale. Caregivers’/proxies’ information was recorded about abil- ity to make decisions, judgment, orientation, short-term memory, and long-term memory. The severity of dementia was rated according to the Clinical Dementia Rating scale. In the present study, only two categories were used: non- demented and demented. The use of the MMSE is a prob- lematic test in the present cohort of centenarians, but for most of the participants with missing MMSE data, other variables could provide the necessary information to assess cognitive function.2 Furthermore, information about ADLs and IADLs and proxy information regarding intellectual abilities made it possible to distinguish disability due to cognitive decline versus physical impairment.

If systemic inflammation is a cause and a consequence of age-related pathology such as dementia, the plasma level of TNF-a will be a marker of the magnitude of the inflam- matory response and the severity of pathology. Moreover, genetic polymorphisms that determine the rate of TNF-a production will be important risk factors. Nine polymorph- isms and five microsatellites in the TNF locus have been characterized.12 The TNF  308 G4A promoter poly- morphism is common, and it has been demonstrated that

of age-related pathology such as dementia, the plasma level of TNF-a will be a marker of the magnitude of the inflam- matory response and the severity of pathology. Moreover, genetic polymorphisms that determine the rate of TNF-a production will be important risk factors. Nine polymorph- isms and five microsatellites in the TNF locus have been characterized.12 The TNF  308 G4A promoter poly- morphism is common, and it has been demonstrated that  308 A is a much stronger transcriptional activator than the more common G allele, but the effect is dependent on the cell line and the stimulus.13 The  308 A allele has been associated with increased lipopolysaccharide-stimulated TNF-a production in whole blood.14 Furthermore, the  308 A allele has been associated with decreased preva- lence of leprosy, in which high circulating levels of TNF-a plays a protective role,15 and increased risk of cerebral ma-

 308 A is a much stronger transcriptional activator than the more common G allele, but the effect is dependent on the cell line and the stimulus.13 The  308 A allele has been associated with increased lipopolysaccharide-stimulated TNF-a production in whole blood.14 Furthermore, the

 308 A allele has been associated with decreased preva- lence of leprosy, in which high circulating levels of TNF-a plays a protective role,15 and increased risk of cerebral ma- laria and autoimmune diseases, in which TNF-a has a det- rimental effect.16 The  308 A allele has also been associated with early onset of AD.17

Thus, a high plasma level of TNF-a may be a marker of dementia and an independent predictor of early mortality risk in centenarians. The purpose of the present study was to test the hypothesis that the TNF  308 A allele is as- sociated with high prevalence of dementia, increased risk of all-cause mortality risk, and elevated circulating levels of TNF-a or inflammatory markers downstream in the in- flammatory cascade (interleukin (IL)-6, IL-8, and C-reac- tive protein (CRP)) in a previously examined cohort of Danish centenarians. Furthermore, whether the TNF  308 A allele was inversely associated with longevity, evaluated by a lower prevalence in centenarians than in octogenarians and young controls, was investigated.

Deoxyribonucleic Acid Extracting and Genotyping

QIAamp mini Spin columns (Qiagen, Hilden, Germany) were used for deoxyribonucleic acid extraction from whole blood that had been stored at  801C. The G to A transition at position  308 was analyzed using a Light Cycler (Roche, Basel, Switzerland) using 3 mM magnesium chlo- ride, 1 mM of TNFUPST: 50-CCT CAA CGG ACT CAG CTT TC-30, 1 mM of TNFDOWST: 50-TCT CGG TTT CTT CTC CAT CG-30, 0.2 mM of TNFUP: 50-TAG GTT TTG AGG GGC ATG GGG AC-30-fluorescein, and 0.2 mM TNFDW: 50-LC Red640-GGG TTC AGC CTC CAG GGT CCT ACA CAC-30-phosphate. Polymerase chain reaction was performed using FastStart DNA Master Mix (Roche), and conditions included 951C for 600 seconds, 45 cycles of 951C for 5 seconds, 661C for 10 seconds and 721C for 20 seconds, followed by a melting curve analysis. The melting temperatures were 851C for the G allele and 651C for the A allele.

MATERIALS AND METHODS

Centenarians