Follow-up of "non-diabetic" relatives of diabetics by retesting oral glucose tolerance after 5 years

Community screening for glucose intolerance in middle-aged Icelandic men. Deterioration to diabetes over a period of 71/2 years

A number of 2203 middle-aged Icelandic men (aged 34-61 years) participated in a health survey in Reykjavik in 1967-68. Blood glucose in the fasting state and during an oral glucose tolerance test (OGTT) showed a unimodal distribution with a slight skewness towards higher values. A positive age gradient was established, which showed an increment of about 7 mg/dl per decade in capillary blood sugar values at 11/2 hours after a 50 g oral glucose load. The age gradient was mostly independent of age-related changes in body weight. A 71/2 year followup of the eligible participants (response rate 80%) showed an overall 1% incidence of metabolic deterioration to "overt diabetes" during this period. Those with positive screening tests (50 g OFTT) at baseline were at greater risk of developing diabetes, but the incidence of deterioration in this group was low, about 1% per year. The progression to diabetes was significantly related to body weight at baseline, suggesting that weight reduction might be beneficial in individuals showing impaired glucose tolerance at medical examination. This study, however, lends support to recent reports showing that mildly impaired glucose tolerance cannot be equated with early diabetes.

Persistent impaired glucose tolerance, insulin resistance, and β-cell dysfunction were independent predictors of type 2 diabetes

BACKGROUND AND OBJECTIVE

To compare clinical profiles and risk of diabetes between subjects with transient (trIGT) and persistent (pIGT) impaired glucose tolerance in Taiwan.

STUDY DESIGN AND SETTING

In the pIGT group, IGT was diagnosed in two consecutive periods (1992-1994 and 1995-1996); in the trIGT group, the diagnosis was IGT at the baseline but normal glucose tolerance in the second period. The normal group was defined by fasting plasma glucose < 6.1 mmol/L and 2-hour post-load plasma glucose < 7.8 mmol/L in both periods. All three groups were considered eligible subjects for further follow up (1998-1999).

RESULTS

Among 298 nondiabetic subjects at baseline, there were 29 new cases of diabetes diagnosed according to 1999 WHO criteria in 1,614.3 person-years of follow-up (1.79%/year; 95% CI = 1.14-2.44%/year). Among subjects with normal, trIGT, or pIGT, the incidence rates were 0.73%/year (8/1,093.0; 95% CI = 0.22-1.24%/year), 2.57%/year (7/272.2; 95% CI = 0.67-4.47%/year), and 5.62%/year (14/249.1; 95% CI = 2.68-8.56%/year), respectively.

CONCLUSION

The group with trIGT had abnormal glucose tolerance and beta-cell dysfunction, which may represent an earlier stage than the group with pIGT in development of type 2 diabetes. Moreover, pIGT, insulin resistance, and beta-cell dysfunction played independent roles in the deterioration from IGT to diabetes.

Predictors of progression from impaired glucose tolerance to NIDDM: an analysis of six prospective studies

Risk factors associated with the progression from impaired glucose tolerance (IGT) to NIDDM were examined in data from six prospective studies. IGT and NIDDM were defined in all studies by World Health Organization (WHO) criteria, and baseline risk factors were measured at the time of first recognition of IGT. The studies varied in size from 177 to 693 participants with IGT, and included men and women followed from 2 to 27 years after the recognition of IGT. Across the six studies, the incidence rate of NIDDM was 57.2/1,000 person-years and ranged from 35.8/1,000 to 87.3/1,000 person-years. Although baseline measures of fasting and 2-h postchallenge glucose levels were both positively associated with NIDDM incidence, incidence rates were sharply higher for those in the top quartile of fasting plasma glucose levels, but increased linearly with increasing 2-h postchallenge glucose quartiles. Incidence rates were higher among the Hispanic, Mexican-American, Pima, and Nauruan populations than among Caucasians. The effect of baseline age on NIDDM incidence rates differed among the studies; the rates did not increase or rose only slightly with increasing baseline age in three of the studies and formed an inverted U in three studies. In all studies, estimates of obesity (including BMI, waist-to-hip ratio, and waist circumference) were positively associated with NIDDM incidence. BMI was associated with NIDDM incidence independently of fasting and 2-h post challenge glucose levels in the combined analysis of all six studies and in three cohorts separately, but not in the three studies with the highest NIDDM incidence rates. Sex and family history of diabetes were generally not related to NIDDM progression. This analysis indicates that persons with IGT are at high risk and that further refinement of risk can be made by other simple measurements. The ability to identify persons at high risk of NIDDM should facilitate clinical trials in diabetes prevention.

Improvement in glucose tolerance after one year of follow-up in a Hindu community in Africa

Oral glucose tolerance was studied following a 75 g glucose load in 108 (82.4%) of 131 male and 110 (79.1%) of 139 female members of a Hindu subcommunity aged 15 years and over in Dar es Salaam. One year later, the glucose tolerance tests were repeated in 93 (86.1%) and 93 (84.5%) of the 108 male, and 110 of the female subjects, respectively. In the first survey, 25 (26.9%) of the 93 male and 24 (25.8%) of the 93 female subjects had impaired glucose tolerance (IGT), 6 (6.4%) and 15 (16.1%), respectively, had diabetes mellitus; and 62 (66.7%) and 54 (58.1%), respectively, had normal glucose tolerance. In the repeat survey, of the 93 male and 93 female subjects, 8 (8.6%) and 7 (7.5%) had IGT, 4 (4.3%) and 10 (10.8%) had diabetes; and 81 (87.1%) and 76 (81.7%) were normal, respectively. Of the 21 subjects diagnosed as having diabetes in the first survey, 13 (61.9%) continued to show diabetic glucose tolerance; 4 (19%) IGT and 4 (19%) had normal glucose tolerance with no gender difference. One (1.6%) of the 62 male subjects and none of the 54 females with normal glucose tolerance in the first survey progressed to IGT, while the remainder retained normal glucose tolerance. Diabetes and IGT rates in both surveys were higher for the older than the younger persons. A significant fall in mean fasting and post-75 g blood glucose levels, and in mean systolic and diastolic pressure levels was observed between the first and second surveys in both genders. There was, however, no significant difference in body mass index (BMI), serum total cholesterol and triglyceride levels between surveys, suggesting that major dietary changes had not taken place. Male subjects who showed persistent IGT had significantly lower mean level of body mass index (kg/m2) than subjects who reverted to normal, whilst for the whole group those who had persistent IGT were older. It is tempting to speculate that these changes were due to community action. However, in view of the lack of change in weight and lipids and similar results in other communities in Tanzania when retested at 1 week, further studies are needed to establish the significance of the findings.

The relationship between glycosylated haemoglobin levels and various degrees of glucose intolerance

To assess the use of glycosylated haemoglobin to discriminate between various degrees of glucose intolerance, glycosylated haemoglobin levels were determined in 107 subjects (48 males and 59 females, age range 18-80 years). Following a 75 g oral glucose tolerance test and according to World Health Organization criteria, subjects were classified as normal (n = 32), diabetic (n = 46) or as having impaired glucose tolerance (n = 29). Mean glycosylated haemoglobin levels were 5.8 +/- 1.3% (range 4%-9%) in normal subjects, 7.1 +/- 1.7% in subjects with impaired glucose tolerance (range 4.1%-10.1%) and 10.1 +/- 2.6% (range 4.7%-18.8%) in diabetic patients. The difference between the groups was highly significant (p less than 0.01). Twelve per cent of normal subjects exceeded and 52% of subjects with impaired glucose tolerance fell below 7.4% (mean +/- 2SD, considered as the upper limit of normal values). A significant correlation was observed between glycosylated haemoglobin values and fasting blood glucose (r = 0.68, p less than 0.01). These results provide evidence that glycosylated haemoglobin levels are influenced by slightly reduced carbohydrate tolerance. Glycosylated haemoglobin may be a useful test to improve the specificity of the oral glucose load to select and to follow-up subjects with impaired glucose tolerance.

[On the prognostic value of the 1-h level in the glucose tolerance test. (Five year follow-up with long-term hospitalised psychiatric patients) (author's transl)]

In 922 long-term hospitalised psychiatric patients the glucose tolerance war examined by 1-h level after oral glucose during a five year follow-up study on cardio-vascular risk factors. We were unable to determine the future development of metabolism with reference to normal findings of the test, borderlines levels ans positively impaired glucose tolerance. But it was to be seen than depending on increasing basic levels the tendency towards a decrease in glucose tolerance increased too. As far as prognosis is concerned, a turning-point for the further development either towards a return to normal or a manifest diabetes seems to be at 180 mg% after 1 h. Above this level, the probability to develop manifest diabetes respectively a higher degree of impaired tolerance has become within a few years, just as great as the probability of a remission. The tendency towards a decreasing glucose tolerance or the manifestation of diabetes was furthered by initial existence or development of a higher overweight (more than 30%).

The reproducibility of the oral glucose tolerance test over long (5 years) and short periods (1 week)

Three oral glucose tolerance tests (oGTT) have been performed in 312 non-diabetic relatives of diabetics over a period of 10 years. In a second study 6 identical oGTT's have been performed at weekly intervals in 55 individuals. In this study the variance, calculated from the logarithmic values, increased in the following order: fasting (0.026), 1 h (0.035), 2 h (0.044) and 3 h values (0.047). The sum of the 1 h and 2 h values showed the lowest variance (0.024). No significant difference of the variances was found in the 43 individuals in whom both the long-term and the short-term studies have been performed. Thus, a great proportion of the total variance of glucose observed over longer periods only represents a random variation. This random variation is much higher than most other factors which might influence the result of an oGTT. A diagnosis based on a single oGTT is of only limited value.

The effect of aging on carbohydrate metabolism: a review of the English literature and a practical approach to the diagnosis of diabetes mellitus in the elderly

There seems little doubt that the disposal of a glucose load is progressively impaired during aging. The mechanism(s) for this alteration remains unclear. Five possibilities have been raised: (1) poor diet, (2) physical inactivity, (3) decreased lean body mass in which to store the carbohydrate load, (4) decreased insulin secretion, and (5) insulin antagonism. Although poor diet and physical inactivity may contribute to some of the abnormal glucose tolerance tests of the older population, these two factors do not provide a full explanation. Diminished lean body mass may play some role but there is almost certainly an additional effect due to aging. A few papers have suggested that glucose-induced insulin secretion may be impaired as the population ages, but the bulk of studies in this area conclude that normal or increased amounts of insulin are released by the pancreatic beta-cell during aging. If abnormalities of insulin secretion exist, either in degree or timing, they are subtle and would not seem sufficient to account for the great number of older subjects who manifest impaired glucose tolerance. The evidence for insulin antagonism seems the strongest but the data are certainly not conclusive. In actuality, the aging effect on carbohydrate metabolism may be heterogeneous in nature. Either some or all of these five factors may contribute to the aging effect to varying degrees in individual subjects. Alternatively, the glucose intolerance of aging may represent a heterogeneous group of disorders. In any event, until better methods to identify possible subgroups of these subjects and/or a marker for diabetes mellitus independent of glucose concentration become available, this problem will remain difficult to resolve. Based on the currently available data, it seems prudent to diagnose diabetes mellitus only if fasting hyperglycemia is present.

Worsening to diabetes in men with impaired glucose tolerance ("borderline diabetes")

Two hundred and four men with impaired glucose tolerance (borderline diabetes) discovered in a screening examination have been observed for five years and repeated tests of glucose tolerance performed. By pre-determined criteria 27 men 'worsened to diabetes' and this metabolic deterioration was not significantly influenced by treatment with carbohydrate restriction with or without a daily dose of 50 mg phenformin. Of the baseline variables measured prior to treatment allocation only the blood glucose values were significantly predictive of ultimate worsening to diabetes.