Table 1.
Discordant-Twin Studies in Social and Psychological Gerontology
| Study and outcome | Exposure | Is there a significant association between exposure and outcome?
|
|||
|---|---|---|---|---|---|
| Individual level (N) | Within twin pairs (N) | Within MZ pairs (N) | Within DZ pairs (N) | ||
| Andel et al. (2005) | |||||
| Dementia | Job complexity | Yes (10,079) | Yes (55) | NR | NR |
| Andel et al. (2008) | |||||
| Dementia | Physical exercise | Yes (3,134) | No (90) | NR | NR |
| Carlsson et al. (2003) | |||||
| Type 2 diabetes | Alcohol consumption | Yes (22,778) | NR | NR | No (27) |
| Carlsson et al. (2007) | |||||
| Mortality | Physical activity | Yes (26,218) | Yes (8,696) | No (3,112) | No (5,584) |
| Crowe et al. (2003) | |||||
| Dementia | Leisure activity | NR | Yes (107) | NR | NR |
| Kujala et al. (2002) | |||||
| Mortality | Exercise | Yes (15,904) | No (658) | No (155) | No (475) |
| Mortality | Smoking | Yes (15,904) | Yes (809) | Yes (166) | Yes (591) |
| Mortality | Heavy alcohol | Yes (15,904) | Yes (507) | Yes (105) | Yes (376) |
| McGue et al. (2007) | |||||
| Physical function | Social activity | Yes (4,731) | NR | Yes (70) | NR |
| Cognitive | Social activity | Yes (4,731) | NR | Yes (70) | NR |
| Depression | Social activity | Yes (4,731) | NR | Yes (70) | NR |
| Osler et al. (2007)a | |||||
| Cognitive | Social class | Yes (2,441) | NR | No (NR) | Yes (NR) |
| BMI | Social class | Yes (2,420) | NR | No (NR) | No (NR) |
| Self-rated health | Social class | Yes (2,441) | NR | No (NR) | No (NR) |
| Osler et al. (2008) | |||||
| Cognitive | Married | Yes (2,270) | Yes (333) | No (NR) | Yes (NR) |
| Smoking | Married | Yes (2,274) | No (333) | No (NR) | No (NR) |
| Depression | Married | Yes (2,270) | Yes (333) | Yes (NR) | Yes (NR) |
| Potter et al. (2007) | |||||
| Dementia | Job complexity | Yes (425) | Yes (220) | NR | NR |
| Stubbe et al. (2007) | |||||
| Life satisfaction | Physical exercise | Yes (8,000) | NR | No (174) | No (162) |
| Waller et al. (2008) | |||||
| 30-year weight gain | Physical activity | Yes (178) | Yes (42) | NR | NR |
Note. NR = Result or sample size not reported.
a
In the Osler et al. (2007) study only the total number of discordant twin pairs was reported (N = 386).