Table 3.
Studies with Twin Discordant for Physical Activity Levels.
| Outcomes | Physical Inactivity Effect | MZ (n) | Other (n) | Sex | PA Measurement | Comments | Ref |
|---|---|---|---|---|---|---|---|
| MRI Visceral Fat | ↑ 50% in inactive Twin | 16 | B | Questionnaire | Age 50–74 years and Followed for over 32 years. Subset for Finnish twin study. | (316) | |
| MRI Liver Fat Score | ↑ 170% in inactive Twin | ||||||
| MRI Intramuscular Fat | ↑ 54% in Inactive Twin | ||||||
| BW changes from 1975 to 2005 | ↑ 5.4 kg for the inactive twin | 42 twins MZ to DZ proportions unclear | B | Phone Interview | Unclear about proportion of MZ vs. DZ, but states no differences between MZ and DZ. Subset of Finnish twin study. Twins not discordant for PA had no difference in BW. | (545) | |
| WC changes from 1975 to 2005 | ↑ 8.4 cm in inactive twin | ||||||
| BMI | ↑ 0.33 BMI in non-vigorously active twin | 614 | M | Self Reported Vigorous Activity | All males (mean age 41.1) that fought in Vietnam war. When looking at all twins modeling predicted no genetic effect on the relationship between vigorous activity and BMI. | (335) | |
| Weight Gain | ↑ 5.4 kg inactive twin | 42 | B | Questionnaire showing Discordant PA in 1975, 1981, and 2005 | Finnish twin study | (545) | |
| Waist Circumference | ↑ 8.4 cm in inactive twin | ||||||
| Total Body fat in women with similar weight | ↑ 1.0 kg& 1.4 kg fat for 1-hr or 2-hr less activity/wk | 156 | W | Questionnaire Home, sport, sweating activities | Discordant for physical activity. Age of 55.5 yr/old | (455) | |
| Total and regional Body fat in women with discordant weight | ↑ 3.96 kg lower BF & 0.53kg central | Also showed increased physical activity increased muscle mass and strength (not analyzed in discordant twins) | |||||
| BMI | ↑ 2.12 in inactive twin (p<0.001) | 35 | Healthy Runners Survey – high PA = 40km/wk > than low PA (male), 32km/wk (female) | Subjects recruited from the National Healthy Runners Survey. No active twins with overweight twin were themselves overweight. | (563) | ||
| HDL | ↓0.14 in inactive (p=0.004) | ||||||
| HDL2 | ↑ 2.71 in inactive (p=0.001) | ||||||
| Apo A-1 | ↑ 0.10 in inactive (p=0.004) | ||||||
| Lipid profile before and after 40% fat or 20% fat diet (cross over study): LDL and sybfractions, apolipoprotein A-1 | N.S. | 28 | M | Survey. One twin running >50km/wk than other twin | Subjects recruited from the National Healthy Runners study. A diet low in fat independent of high amounts of exercise modifies circulating lipids. | (564) | |
| Adiposity | ↑ Sig lower in inactive twin | 21 | F | 9 months of 3xwk high intensity weight bearing activity | Girls were prepubertal aged 8.7. Did not tell the control group that they could no longer participate in sports. | (534) | |
| BMD | N.S. | 12 | Lifetime leisure high-impact sports | Subgroup from the original group. | |||
| aBMC | ↓ Sig in inactive twin | ||||||
| Femoral neck and lumbar BMD | E = 1%&G = 73% of lumbar variance | 105 | M | Questionnaire for endurance and balls sports | Finnish men (35–69yr/old)Calcium supplements also explained 1% of difference in BMD. | (541) | |
| Spinal MRI | N.S. disk degeneration | 22 | M | Questionnaire between 1975 and 1981 showing discordant endurance PA (3.9 v 1.1 time/wk) | Finnish Twin Cohort aged 35–69 | (542) | |
| ↓T6-T12disk degeneration in low strength PA twin | 12 | Questionnaire between 1975 and 1981 showing discordant strength PA (2300 v 200 hrs) | |||||
| Psychomotor reaction times | ↓ Sig slower choice reaction for hand & contra foot in inactive | 38 | Lifetime exercise histories | Finnish twin cohort. Average age of discordant PA twins is 50. PA data collected in 1972, 81, 92 | (475) | ||
| Psychological functioning (mood, optimism, control) | ↓ Sig in inactive twin | 63 | B | Questionnaire for discordant vigorous activity | From US National Survey of Midlife Development | (258) | |
| Survey based Anxiety and Depression symptoms | N.S. | ? | ? | B | Leisure time PA only | Article is unclear how many MZ twins were discordant for PA in their models. Only current levels of PA and not PA history used. Used Dutch population, but excluded cycling to work as PA (non-leisure) | (126) |
| Dementia | ↑ P = 0.07 for inactive PA twin | 90 | B | Twin registry reported 31 years before follow-up | Swedish twin registry. Data on all twins showed significant correlation of increased PA and decreased dementia | (12) | |
| Life satisfaction | N.S. | 161 | 172 | 2842 | Survey | Data in MZ and related family members showed an OR>1.0for active pair of an unrelated paired of people. | (498) |
| Life Happiness | N.S. | ||||||
| Lactate threshold | E is 25–30% & G is 50–60% | 9 | M | 6 months of anaerobic threshold training | Aged 11–14. Change in VO2max was more due to the less weight gain in trained twin. Used analysis of variance to estimate the genetic and training effects. | (119) | |
| VO2max | E is 35% & G is 45% | ||||||
| Total Body Fat | E is 20% & G is 70% | ||||||
| Myocardial infusion at rest, during adenosine, and cold-presser test | N.S. | 9 | M | Separated by VO2max and physical activity levels | Young males with a 18% difference inVO2max (ml/kg/min) of (43.7 vs 50.7) | (221) | |
| Endothelial function via ultrasound of brachial and LAD coronary artery | N.S. | ||||||
| Oxygen extraction fraction | ↑ in low fit (p=0.06) | ||||||
| Hepatic FFA uptake at rest | ↑Sig in less fit group | Same subjects as above. | (222) | ||||
| Myocardial FFA uptake at rest and during exercise | N.S. | ||||||
| Skeletal muscle perfusion and free fatty acid uptake | N.S. | Same subjects as previous study. | (223) | ||||
| Cornell voltage (electrical measurement of LV hypertrophy) | ↓Sig in inactive | (36) | |||||
| Right-side hypertrophy index | |||||||
| LV mass index | |||||||
| Type 2 Diabetes | 18 inactive v 2 active twins acquired T2DM | 5 | 15 DZ | B | Leisure time PA | Twins discordant for PA and discordant for Type 2 diabetes. For MZs it was the inactive twin that developed type 2 diabetes. | (288) |
| Mortality from 1975–1981 | ↑Sig in inactive DZ twins, but not inactive MZ twins | 157 | 517 | B | Questionnaires for vigorous PA and estimates of >2MET wk/day/wk | Finnish twin cohort aged 24–60. Low level of leisure physical activity in early life was associated with increased risks of death in dizygotic twin pairs, but monozygotic co-twins. | (289, 546) |
B = both sexes; DZ = dizygotic; E = exercise component; G = genomic component; M = men; MZ = monozygotic; N.S. = non-significant; PA = physically active; W = women; ↑ = increase; ↓ = decrease