Dc. Muller et al., INSULIN-RESPONSE DURING THE ORAL GLUCOSE-TOLERANCE TEST - THE ROLE OFAGE, SEX, BODY-FAT AND THE PATTERN OF FAT DISTRIBUTION, Aging, 8(1), 1996, pp. 13-21
To clarify their primary roles on insulin response to oral glucose, ag
e and sex differences in body composition should be taken into account
. Oral glucose tolerance rests were performed on 472 men and 299 women
of the Baltimore Longitudinal Study of Aging, ranging in age from 20
to 96 years. Subjects who were taking medications or had any diseases
which could affect glucose tolerance were excluded. In addition to ins
ulin and glucose values for the glucose tolerance test, we calculated
body mass index (BMI), percentage body fat from skinfolds (% Body Fat)
, waist hip ratio (WHR), mean glucose level over the 2-hour test (G(M)
), the basal insulin (I-o), and the mean insulin response over the 2-h
our test (I-M). There was no significant sex difference in mean age, b
ut men had significantly higher BMI (25.6 vs 24.0 kg/m(2)), WHR (0.93
vs 0.76), and G(M) (8.5 vs 7.7 mM), while % Body Fat was lower (25% vs
33%). Unadjusted I-o and I-M levels were significantly higher in men
than in women (51 vs 44 and 303 vs 231 pM - antilogs of log-normalized
values). Insulin levels, adjusted for differences in age, % Body Fat,
WHR, and G(M) by analysis of covariance, however, showed no sex diffe
rences (49 vs 46 and 282 vs 257 pM). Adjusted insulin levels declined
significantly with age; I-M fell progressively from 323 pM in 20 to 39
-year olds, 267 pM in 40 to 59-year, 253 pM in 60 to 79-years, and 228
pM in 80 to 96-year olds (p<0.01). We conclude that the sex differenc
es in insulin levels are explained by differences in body habitus and
post-load glucose levels, but that insulin levels decline with age per
se.