Ronald E. LaPorte

Development of Questionnaire to Examine Relationship of Physical Activity and Diabetes in Pima Indians

There was a need to design a questionnaire that could accurately assess the activity patterns of Native Americans to evaluate the relationship between physical activity and diabetes. Such a questionnaire was developed and implemented into the data collection scheme of the prospective Pima Indian Study of Arizona. The questionnaire, which assesses historical, past-year, and past-week leisure and occupational activity, was examined in 29 Pima individuals aged 21–36 yr and was shown to be reliable with test-retest correlations (rank-order correlations ranged from 0.62 to 0.96 for leisure and occupational activity). Reproducibility of the past-year leisure physical-activity estimate was determined in 69 participants aged 10-59 yr and was found to be reliable in all age-groups with the exception of the 10- to 14-yr-old age-group (rank-order correlations were 0.31 in the 10- to 14-yr-old age-group compared to 0.88 to 0.92 in those >20 yr of age). Validity of the current-activity section of the questionnaire was demonstrated indirectly through comparisons with activity monitors. The past-week leisure-activity estimate was related to the Caltrac activity monitor counts per hour (p = 0.62, P > 0.05, n = 17). In summary, a physical-activity questionnaire has been developed that is both reliable and feasible to use in the Pima Indian population to evaluate the relationship of physical activity to non-insulin-dependent diabetes mellitus.

Prevalence of Complications in IDDM by Sex and Duration: Pittsburgh Epidemiology of Diabetes Complications Study II

The prevalence of and interrelationships among all four major complications of insulin-dependent diabetes mellitus (IDDM) and their risk factors are being examined in a large epidemiologic study of IDDM subjects diagnosed in childhood. This article focuses on the baseline prevalence of complications in the 657 subjects diagnosed between 1950 and 1980 and currently aged 8–48 yr, with a mean duration of 20 yr. In addition to background retinopathy being virtually universal after 20 yr of diabetes, proliferative retinopathy affects 70% of IDDM subjects after 30 yr duration. As with overt nephropathy, prevalence of proliferative retinopathy is marginally higher in females than in males at short durations; the previously reported male excess is limited to the subjects with IDDM of longer duration (≥25 yr). Somewhat different patterns of microalbuminuria are also seen by sex. Males show a threefold increase in prevalence from 10 to 25 yr duration, whereas females show a more constant prevalence across these durations. A further rise in microalbuminuria is seen in males but not females at ≥30 yr duration, giving a combined prevalence of microalbuminuria and overt nephropathy at ≥30 yr duration of 84% (males) and 59% (females). Distal symmetrical polyneuropathy shows a constant rise with duration and is only marginally higher in men. Prevalence of cardiovascular (coronary and cerebral) disease shows no sex difference, whereas peripheral vascular disease is particularly common in women after 30 yr duration (>30%) compared with men (11%) when determined by ankle/arm blood pressure ratio <0.8 at rest or after exercise. These results suggest that the natural history of IDDM complications varies considerably by sex and that the prevalence of complications (especially renal complications in males) may be higher than previously recognized.

A review of the recent epidemiological data on the worldwide incidence of type 1 (insulin dependent) diabetes mellitus

SummaryNearly 70 registries from more than 40 countries have collected and published incidence data of childhood Type 1 (insulin-dependent) diabetes mellitus up to the end of the 1980s. The majority of incidence data comes from regions of high incidence i. e. from Europe and North American. All these published data facilitate the descriptive comparison of incidence and variation of the occurrence of Type 1 diabetes roughly throughout the northern hemisphere. The aim of this paper is to review and compare the most recent epidemiology data on the incidence of Type 1 diabetes among children under the age of 15 years. A clear difference in incidence appeared between northern and southern hemisphere with no countries below the equator having an incidence greater than 15.0 per 100,000. In contrast above the equator the disease is common. Between continents the variation in incidence showed that the lowest incidences were found in Asia, followed by Oceania (Australia and New Zealand), South and North America, and the highest rates were in Europe. The incidence varied from 0.6 per 100,000 in Korea and Mexico to 35.3 per 100,000 in Finland showing prominent worldwide variation in incidence of Type 1 diabetes. The largest intracontinental variation in incidence appeared in Europe, varying from the highest in Finland to the lowest (4.6 per 100,000)_in northern Greece. The highest incidence in the world was in northern Europe, but within the continent scale there were some striking exceptions from the overall level of incidence. In Iceland, the northern-most island nation in Europe, the incidence is only one-half of that in Norway and Sweden and one-third of that in Finland. In contrast, in Sardinia in southern Europe the Type 1 diabetes incidence is virtually the same as in Finland, three times higher than overall incidence in Europe. Large variation was also seen in small “pockets” of countries, particularly in the Baltic sea region. The worldwide variation in incidence reflects the distribution of ethnic populations and demonstrates the importance of the differential genetic susceptibility between populations.

The Pittsburgh Insulin-dependent Diabetes Mellitus (IDDM) Morbidity and Mortality Study: Mortality Results

A follow-up study of 1966 patients with insulin-dependent diabetes mellitus (IDDM) who were diagnosed at Childrens Hospital of Pittsburgh (CHP) between 1950 and 1981 has been completed. The mean age of the population at follow-up was 21.2 yr with a mean duration of IDDM of 12.9 yr. Nine percent of the patients were deceased, a sevenfold excess in mortality compared with the U.S. population. The relative increase in mortality was greater for females than males and greater for blacks than whites. Before age 20, the primary excess in mortality was at onset of IDDM, or within 6 mo after onset, and was due to acute diabetic complications. After age 20, the annual mortality risk was approximately 2%, which was more than 20 times greater than for the U. S. population. Renal disease was responsible for the majority of these deaths. There was a reduced risk of dying for diabetic patients who were diagnosed between 1966 and 1971 compared with patients diagnosed during earlier years.

The epidemiology of low back pain in an adolescent population.

We assessed the prevalence of low back pain (LBP) in a cohort of 1242 adolescents (aged 11 through 17) currently participating in a 4-year prospective study of medically treated injuries. Overall, 30.4% of the adolescents reported LBP. The impact of LBP in adolescents was considerable, with one third resulting in restricted activity and 7.3% seeking medical attention. Life-table analysis demonstrated that by age 15, the prevalence of LBP increased to 36%. There were few differences by gender or race. These results suggest that LBP in adolescents is a serious public health problem.

The epidemiology of leisure physical activity in an adolescent population.

A cohort of 1245 adolescents, 12-16 yr old and participating in a prospective study of risk factors for injury, were surveyed annually to assess past year leisure physical activity. This report describes the development and reproducibility of the questionnaire and provides the descriptive epidemiology of leisure physical activity in adolescents. The questionnaire was self-administered twice, a year apart, and had a 1 yr test-retest rank order correlation of 0.55. The past year estimate of leisure activity was also shown to be related to fitness (rho = -0.37), which was defined as the time needed to complete a 1-mile run. Males reported significantly more activity than females (P < 0.05) and whites reported more activity than nonwhites (P < 0.05). However, socioeconomic status was not found to be a determinant of activity levels in either males or females. In females, a negative association between activity and age was found (P < 0.05); however, this association was not evident in males. In summary, an activity questionnaire has been developed and was shown to be both reproducible and feasible. Therefore, it was used to examine habitual leisure physical activity patterns of adolescents.

Contribution of Diabetes Duration Before Puberty to Development of Microvascular Complications in IDDM Subjects

The contribution of diabetes duration, both pre- and postpuberty, to the development of microvascular complications and mortality in diabetic subjects was investigated in three study populations from the Childrens Hospital of Pittsburgh Insulin-Dependent Diabetes Mellitus (IDDM) Registry. Life-table analyses by total and postpubertal IDDM duration were used to evaluate differences in the prevalence of microvascular complications and diabetes-related mortality in subjects diagnosed before and during puberty, as defined by an age at IDDM onset marker of 11 yr for girls and 12 yr for boys. The prevalence of retinopathy and overt nephropathy in 552 White adult diabetic subjects (population 1, mean IDDM duration 20.8 yr) was significantly greater in subjects diagnosed during puberty compared with those diagnosed before puberty. However, similar analyses by postpubertal duration showed no difference in microvascular complication prevalence between the two groups. These findings did not appear to be due to a confounding effect of age. Additional analyses of 239 adolescent diabetic subjects (population 2, mean duration 8.3 yr) revealed the same trend for the prevalence of retinopathy. Finally, results concerning the risk of diabetes-related mortality in a cohort of 1582 subjects (population 3, mean duration 12.9 yr) indicated that postpubertal duration of IDDM may be a more accurate determinant of the development of microvascular complications and diabetes-related mortality than total duration, and it is suggested that the contribution of the prepubertal years of diabetes to long-term prognosis may be minimal.

Geographic differences in the risk of insulin-dependent diabetes mellitus: the importance of registries.

There are marked geographic differences in the incidence of insulin-dependent diabetes mellitus (IDDM); for example, children in countries such as Finland are over 35 times more likely to develop IDDM than children in Japan. An understanding of the reasons for the geographic differences is likely to be important for understanding and, hopefully, preventing IDDM. There are problems, however, because of the lack of registries with adequate standardization. The major needs for the future studies include (1) to clarify the definition of IDDM for epidemiologic study, (2) to establish a standardized approach for IDDM registries, (3) to use registries to evaluate viral, immunologic, and genetic differences in order to explain differential risks across populations, and (4) to encourage the development of new population-based registries worldwide.

The Pittsburgh Study of Insulin-Dependent Diabetes Mellitus: Risk for Diabetes Among Relatives of IDDM

AN analysis has been made of the family histories of a survey of 1280 cases of IDDM entering Childrens Hospital of Pittsburgh between December 31, 1964 and January 1, 1981, discharged on insulin and initial age of onset under 17 yr. Family histories revealed an increased occurrence of IDDM among relatives in the affected families. The risk to siblings was estimated by age-corrected proband exclusion (3.3%) by age 20 and by the Li-Mantel segregation ratio estimator (6.0%). The comparison of these risk measures is discussed. The occurrence of IDDM among the parents is 2.6% and of NIDDM among the parents is 2.4%. A comparison of risk to relatives (parents, sibs, uncles, half-sibs) observed in the Pittsburgh Study to those of six other studies reveal essentially equivalent rates. There is no increased risk to siblings of a diabetic who had an early age of onset. There is an increased risk to siblings of a diabetic (10.5%) in families where at least one parent has insulin-dependent diabetes mellitus (IDDM) and also an increased risk to siblings of a diabetic (8.8%) when at least one parent has non-insulin-dependent diabetes (NIDDM). The average age of onset for second cases in a family is significantly older than age of onset in single case families.

Factors Associated With Avoidance of Severe Complications After 25 Yr of IDDM: Pittsburgh Epidemiology of Diabetes Complications Study I

To identify characteristics associated with long-term avoidance of insulin-dependent diabetes mellitus (IDDM) complications, subjects taking part in an epidemiologic natural history study of childhood-onset IDDM, with a duration of disease ≥25 yr, were studied. Nineteen percent of 175 subjects had avoided overt nephropathy, definite cardiovascular and peripheral vascular disease, clinical neuropathy, and proliferative retinopathy. Approximately half of the nonrenal complications occurred in the absence of renal disease. Subjects free of these advanced complications were characterized by a longer duration of disease (P < 0.05), better lipid profile and blood pressure (P < 0.01), and considerably lower glycosylated hemoglobin levels (P < 0.001). Health-related behaviors, including recent medical contact, regular glucose monitoring, physical activity in youth, and avoidance of cigarette smoking, did not relate to complication status, although regular (at least weekly) alcohol consumption was more prevalent (P < 0.05) in those without complications. We conclude that a lower mean glycosylated hemoglobin level is strongly related to the avoidance of all IDDM complications.