WHO has reported that physical inactivity (PA) is the 4th risk factor of non-communicable diseases. Despite the well-known health benefits of PA, it is apparent that almost population may not be sufficiently active to derive these benefits. Recently, previous studies in western countries reported that genetic factors associated PA. However, in Asia population, that has been unclear yet. The objective of present study was to estimate the heritability of PA by using twin study.

Participants were members of the Osaka University Aged Twin Registry. Our sample included 856 twins (313 men and 543 women, mean age 59.3±20.1). Ethical approval for the study was obtained from the Osaka University Ethics Committee.

PA and sedentary behavior were assessed by the Japanese short version of the International Physical Activity Questionnaire. Participants answered about intensity, frequency and duration of their PA for one week. Derived phenotypes were: vigorous PA (VPA); moderate PA (MPA); walking (WPA); total PA (TPA); sitting time (ST).

Structural equation modelling analysis was performed to evaluate the relative importance of genes and environments for the phenotypes measured.

When different genetic models were compared, the additive genetic/specific environment (AE) model offered the best fit according to Akaike Information Criterion. For WPA, 42% of the variance was explained by additive genetic effects and 58% was by unique environmental (including error) effects. For ST, 19% of the variance was explained by additive genetic effects and 81% was by unique environmental effects. There were no significant additive genetic effects in VPA, MPA, and TPA.

We conclude that walking and sedentary behavior influenced by additive genetic factors in Japanese adults. These results would help us provide an appropriate approach for people to be physically active. This work was supported by MEXT KAKENHI; 16K21530, 16K15385, 16K15978, and 16K15989.