Effects of 32-Year Leisure Time Physical Activity Discordance in Twin Pairs on Health (TWINACTIVE Study): Aims, Design and Results for Physical Fitness

Abstract

T he physically active lifestyle is associated with low future morbidity and mortality, but the causality between physical activity and health is not always clear. As some inherited biological characteristics and childhood experiences may cause selection bias in observational studies, we sought to take them into account by identifying 16 twin pairs (7 MZ, 9 DZ, mean age 60 years) discordant for leisure time physical activity habits for thirty years. We conducted detailed health-related examinations among these twin pairs. Our main aims were to study the effects of physical activity and genes on fitness and body composition, with special reference to body fat compartments, metabolic syndrome components and related diseases and risk factor levels, status of arteries, structure and function of the heart, bone properties, and muscle and fat tissue-related mechanisms linked to physical activity and chronic disease development. Our physical activity assessments showed that inactive co-twins were on average 8.8 MET hours/day less active than their active co-twins through out their midlife (2.2 ± 2.3 vs. 11.0 ± 4.1 MET h/day, p < .001). Follow-up fitness tests showed that physically inactive co-twins were less fit than their active co-twins (estimated VO 2peak 26.4 ± 4.9 vs. 32.5 ± 5.5 ml/kg/min, p < .001). Similar differences were found in both MZ and DZ pairs. On the basis of earlier epidemiological observations on nonrelated individuals, these physical activity and fitness differences are large enough to cause differences in many mechanisms and risk factors related to the development of chronic diseases and to permit future analyses.

Physically active vs. inactive lifestyle, muscle properties, and glucose homeostasis in middle-aged and older twins

“…The baseline was the year 1975, when the first physical activity data were available, but it is probable that the discordance in physical activity had begun earlier. We used structured physical activity questionnaire which has shown high reliability in previous studies (Kujala et al 1998;Kujala et al 2002;Waller et al 2008;Leskinen et al 2009a). Although we used validated methods to document leisure-time physical activity, subject's understanding on what leisure-time physical activity is may have changed over time.…”

“…The most common types of physical activity engaged in by the active twins during the previous 12 months were walking (30 % of total physical activity volume), jogging (11 %), and cross-country skiing (9 %). At the end of the follow-up, the co-twins did not differ in work-related physical activity and alcohol or tobacco use, and they had only minimal difference in their daily energy intake (Leskinen et al 2009a;Rintala et al 2011). …”

“…Recall was anchored to relevant life-events. Twin pairs with consistent discordance in physical activity habits throughout the follow-up were invited to participate in the TWINACTIVE study measurements held in 2007 (Leskinen et al 2009a). Overall, 16 samesex middle-aged and older twin pairs (seven monozygotic (MZ) and nine dizygotic (DZ) pairs, five female and 11 male pairs, age range 50-74 years) were able to participate in the measurements and were discordant for physical activity at every time point at which their physical activity habits were assessed.…”

“…Leisure-time activity was quantified as metabolic equivalent units (average intensity of activity (MET) × average duration of one session (in hours) × (monthly frequency / 30 days)) and expressed as the sum score of leisure-time MET hours per day (Kujala et al 1998;Waller et al 2008;Leskinen et al 2009a). …”

Leisure-time physical activity and high-risk fat: a longitudinal population-based twin study

“…Finally, 16 twin pairs fulfilled all our study inclusion criteria, volunteered to participate in the study measurements and were discordant for leisure-time physical activity on the basis of the detailed physical activity interview conducted in 2007. 19 Validity data of physical activity questionnaire and interviews are available in our earlier reports. 17,19 Altogether, there were four cross-sectional (1975, 1981, 2005 and 2007) and five retrospective time-points at which the active cotwins reported to have a higher physical activity level compared with the inactive co-twins (Po0.005 for all timepoints for the leisure MET index difference between inactive and active co-twins) ( Figure 1 Smoking habits and use of alcohol, together with other confounders, were collected with diary, questionnaire and interview methods as described earlier.…”