Determinants of psychomotor speed among 61 pairs of adult male monozygotic twins.
BACKGROUND
Declining psychomotor speed is an indicator of the aging process, and it is influenced by genetics and environmental factors. The present study examined the relative effects of familial aggregation (reflecting a combination of genetics and early environmental influences), and occupational, lifestyle, and health factors on psychomotor speed.


METHODS
Hand and foot psychomotor speed was studied with 61 pairs of monozygotic male twins aged 35-67 years from the population-based Finnish Twin Cohort. The determinants of visual simple and choice reaction times were analyzed with multiple regression analysis.


RESULTS
Familial aggregation, reflecting genetic influences and shared environmental effects, explained in mean 47% of decision times, 31% of movement times, and 37% of response times (decision time and movement time combined). Age, cardiovascular morbidity, lifetime vigorous and frequent exercise participation, and mean lifetime daily hours sitting at work explained 0-19% of hand psychomotor speed and 0-10% of foot speed, depending on the outcome. The predicted increase in decision times due to the presence of cardiovascular morbidity was 11-35 ms. The predicted increase for hand and contralateral foot response times between ages 45 and 55 was 18-41 ms. Smaller effects were noted for each year of strenuous exercise and each hour/day of average lifetime sitting at work.


CONCLUSIONS
Results indicate that cardiovascular status, age, strenuous exercise, and work play a role in psychomotor speed, but a rather minor one. In contrast, genetic and shared early environmental influences as revealed from familial aggregation were relatively strong, yet a major proportion of the variability in psychomotor speed remained unexplained.
Simonen
R L
RL
Department of Health Sciences, University of Jyväskylä, Finland. rsimonen@cc.jyu.fi
Videman
T
T
Battié
M C
MC
Gibbons
L E
LE
D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000375:Aging / Q000235:genetics* / Q000502:physiology; D002318:Cardiovascular Diseases / Q000453:epidemiology* / Q000503:physiopathology; D015331:Cohort Studies; D003657:Decision Making / Q000502:physiology; D015444:Exercise; D005528:Foot; D007839:Functional Laterality; D006225:Hand; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D012907:Smoking; D014430:Twins, Monozygotic