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Cohort: Origins of Variance in the Old-Old: Octogenerian Twins
Website: http://ki.se/ki/jsp/polopoly.jsp?d=13903&a=30151&l=en
Risk Factors: Diabetes Mellitus,
Obesity

Introduction to the Cohort
The Origins of Variance in the Oldest-Old (OCTO-TWIN) study is a longitudinal study of twin-pairs drawn from the Swedish Twin Registry (STR). The study aimed to investigate the etiology of individual differences among this subset of the “oldest-old” on a range of domains including health and functional capacity, cognitive functioning, psychological well-being, personality and personal control, and interpersonal functioning.

OCTO-TWIN began in 1991 and included all twins from the STR who were at least 80 years old during the baseline period (1991-1994) who agreed to participate. At baseline, 351 twin-pairs (702 individuals) were available. Twin pairs were followed until 1999. There were three follow-up visits, each approximately 2 years apart during this period.

As all individuals in OCTO-TWIN are part of the STR, information regarding health-related behaviors such as smoking, diet, physical activity, personality and exposure to environmental stressors will be available for some individuals from earlier STR questionnaires sent to members in 1961, 1963, 1967, 1970 and 1973. Questionnaires were also sent to cohort members over the course of the study.

OCTO-TWIN is one of a number of aging studies conducted within the STR. Other STR-based studies include the Swedish Adoption and Twin Study of Aging (SATSA) and the Study of Dementia in Swedish Twins (HARMONY; a subcohort of participants who were at least 65 years old in 1998).

Ethnicity Breakdown
All participants were born in Sweden. While this study did not specifically report any information on ethnicity, another study that used a cohort made up of subsamples from the Swedish Twin Registry has described the OCTO-TWIN participants as Caucasian (Jansson et al., 2003).

Diagnosis & Evaluation Methods
For descriptions of OCTO-TWIN procedures, please see Hassing et al. 2002 and McClearn et al. 1997. For detailed descriptions of the structure of the Swedish Twin Registry, see Lichtenstein, et al. 2002 and Lichtenstein et al. 2006.

References
Hassing LB, Johansson B, Nilsson SE, et al. Diabetes mellitus is a risk factor for vascular dementia, but not for Alzheimer’s disease: a population-based study of the oldest old. Int Psychogeriatr 2002; 14: 239–48.

McClearn GE, Johansson B, Berg S, et al. Substantial genetic influence on cognitive abilities in twins 80 or more years old. Science 1997; 276:1560–1563.

Jansson M, Gatz M, Berg S, et al. Association between depressed mood in the elderly and a 5-HTR2A gene variant. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics 2003; 120B: 79–84.

Lichtenstein P, De Faire U, Floderus B, et al. The Swedish Twin Registry: a unique resource for clinical, epidemiological and genetic studies. J Intern Med 2002; 252: 184–205.

Lichtenstein P, Sullivan PF, Cnattingius S, Gatz M, Johansson S, Carlström E, Björk C, Svartengren M, Wolk A, Klareskog L, de Faire U, Schalling M, Palmgren J, Pedersen NL. The Swedish Twin Registry in the third millennium: an update. Twin Res Hum Genet. 2006 Dec;9(6):875-82.