Effect of Age and Environmental Factors on Glucose Tolerance and Insulin Secretion in a Worker Population

Abstract

The effect of age on glucose tolerance, as differentiated from the effects of obesity, work and leisure physical activity, family history of diabetes, and the use of drugs known to adversely affect glucose tolerance and/or insulin secretion, has been analyzed in 732 factory workers aged 22 to 73 years. Glucose tolerance, as evaluated by the plasma glucose response to 75 g of oral glucose deteriorated with age, associated with an increase in plasma insulin levels. However, the age-related decrease in glucose tolerance also correlated significantly with degree of obesity, leisure-time physical activity, and the use of potential diabetogenic drugs. Partial correlation coefficients were calculated to define the effect of age per se on glucose tolerance, controlling for the presence of these other age-related variables. When this was done, the degree of correlation between age and glucose tolerance was reduced, particularly in women, to where it became of marginal statistical significance. The effect of age on insulin response was affected to a greater degree by age-related variables, and was no longer statistically significant when these other factors were taken into consideration. These data suggest that the elevation in plasma glucose and insulin levels associated with age are to a certain extent due to age-related environmental factors, and the deterioration in glucose tolerance with age is relatively modest in magnitude in a generally healthy population.

The prevalence and risk factors for age-related macular degeneration in rural–urban India, Sankara Nethralaya Rural–Urban Age-related Macular degeneration study, Report No. 1

“…The relationship between ageing, body composition, activity and glucose tolerance was also examined in 270 female and 462 male factory workers aged 22-73, none of whom was retired (183). Plasma glucose levels, both fasting and after a glucose load, increased with age, but the correlation between age and total integrated glucose response following a glucose load was weak; in women, only 3% of the variance could be attributed to age.…”

Age and Glucose Intolerance

“…When adjusted for differences in body weight and physical activity, they found no significant correlation between age and plasma glucose response in men, and differences in age could account for no more than 6% of the variability in glucose response in women. Similarly, when adjusted for differences in weight, physical activity, and use of diabetogenic drugs, age only accounted for 6% of the variance in plasma glucose response to an oral glucose challenge in men and 1% in women in a study of 732 Italian factory workers aged 22-73 years (5). Perhaps the most definitive information in this regard is the results of the Baltimore Longitudinal Study of Aging (6), performed in 743 healthy individuals, comparing glucose tolerance in three age groups: 17-39, 40 -59, and 60 -92 years.…”

“…The effect of age on insulin secretory function in humans has not been as well defined. On the one hand, the plasma insulin of an oral glucose challenge in older individuals is usually greater than or equal to that in matched younger subjects, and the glucose intolerance reported to occur with aging is not associated with an absolute decrease in plasma insulin concentrations (4,5,8,12). However, it appears that older humans do not have the ability to increase insulin secretion to the degree necessary to prevent some degree of glucose intolerance from developing.…”

Carbohydrate metabolism in the elderly

“…The Baltimore Longitudinal Study of Aging also has shown a positive cross-sectional correlation between age and fasting plasma glucose in both men and women (Muller et al, 1996;Shimokata et al, 1991). Zavaroni et al (1986) demonstrated an age-related increase in fasting glucose levels in Italian factory workers; this was signi®cantly reduced in women after adjustments were made for the presence of other agerelated variables. Small increases in fasting glucose levels with age were noted in 4170 men and women living in suburban California (0.7 mgadladecade in men; 2.0 mgadladecade in women) (Barrett-Connor, 1980).…”

“…However, the decline from mid-life to old age (60 ± 92 y) was still in¯uenced by chronological age. In a population of Italian factory workers (Zavaroni et al, 1986) age-related environmental factors (obesity, physical activity, diabetogenic drug use) accounted for a large portion of the decline in glucose tolerance in women, but not in men. Maneatis et al (1982) found that after adjustment for obesity and activity there was an independent effect of age on the decline in glucose tolerance in women.…”