Yue-Fang Chang

Childhood Diabetes in China: Enormous variation by place and ethnic group

OBJECTIVE To investigate the incidence rate of IDDM in China. RESEARCH DESIGN AND METHODS The Chinese IDDM registry was established in 1991 as part of the World Health Organizations Multinational Project for Childhood Diabetes (DiaMond) project. Twenty-two centers were developed to monitor the incidence of IDDM in children <15 years of age. The population under investigation includes >20 million individuals, representing ∼7% of the children in China. Capture-recapture methods were used to estimate the ascertainment. RESULTS The overall ascertainment-corrected IDDM incidence rate in China was 0.51 per 100,000, the lowest rate ever reported. There was a 12-fold geographic variation (0.13–1.61 per 100,000). In general, the incidence rate was higher in the north and the east. There was a sixfold difference among ethnic groups (highest: Mongol group, 1.82 per 100,000; lowest: Zhuang group, 0.32 per 100,000). CONCLUSIONS China has an extremely low overall IDDM incidence rate. China also has the greatest geographic and ethnic variation seen for any country.

Estimating the lesbian population: a capture-recapture approach

Study objective: Little is known about the number of women who identify as lesbian. Estimates from the US range from 1% to nearly 10%. Accurate estimates are critical in order to meet lesbian’s healthcare needs and to address health problems that may be more prevalent among them. This study used capture-recapture methods to estimate the lesbian population of Allegheny County, Pennsylvania. Design: Mailing lists from four sources were used to identify lesbians. The capture-recapture method and log-linear modelling were used to estimate the number of lesbians in the defined geographical area, and the percentage of the female population they comprised there was determined through census data. Setting: Allegheny County, Pennsylvania, USA. Results: A total of 2185 unique names were identified. The capture-recapture method estimated that the total lesbian population of Allegheny County was 7031 (95% CI 5850 to 8576). Therefore, based on the 1990 census figures, the county’s adult lesbian population was estimated to be 1.87% (95% CI 1.56% to 2.28%) of the adult female population. Conclusions: An estimate of the lesbian population is fundamental for addressing lesbian’s health needs and for developing appropriate research programmes. Capture-recapture methods have the potential to provide accurate and reliable estimates of this population in any location.

Epidemics of type 1 diabetes in China

Objective:  The aim of this study was to search for the seasonal and geographic variations in epidemics of type 1 diabetes in China.

Use of the capture-recapture method for epidemiological studies in determining prevalence.

We read the paper by Taba and Asser (1) with great interest. Their investigation determined the prevalence rate of Parkinson’s disease (PD) for the Providence of Tartu in Estonia using various sources that provided lists of patients. As mentioned in the paper, they obtained data from general practitioners, hospitals, nursing homes, the PD Society and the Sick Fund . These sources are lists of cases. Besides using the traditional methodology for determining prevalence rates for a disease, there is another method, the capture– recapture method (CRM) (2–4), that can ascertain prevalence rates, which uses lists. Since it is impossible to ascertain all cases of a disease, the CRM will allow estimation of the undercount to be included in the prevalence rate (4). The CRM has been used in counting wildlife for decades (5, 6) and has been recently applied to epidemiological studies (5). This method, however, is not limited to these two fields of study, but can be applied to any type of counting as long as lists are pooled from the same potential population (7). Unfortunately, for most populations it is impossible to count all individuals and when attempting to do so there will be an undercount. For some populations, like people with certain chronic (e.g. multiple sclerosis) (8) and infectious (e.g. SARS) (9) diseases the undercount may be large because they may be treated in different centers or by private specialized practitioners. There are three methods that can be employed for a CRM (10). The first is the simplest and employ a two-source method for calculations (Fig. 1). One of the difficulties in using the twosource method is the number of assumptions required (10). These include an equal chance of all individuals being selected for both lists (independence), individual identifiers not being lost or missed in the process and the samples (cases) exist in a closed population. The most important of these assumptions is independence, especially since people (cases) may tend to migrate to a specialist, resulting in an overcount or undercount bias. The other two methods are the log-linear and Bernoulli (also called the Wittes method) (10). The most commonly used of these two methods is the loglinear. This method allows determination of the missing data (total number of cases) from a contingency table (Fig. 2). The sources, which have to be three or more, do not have the requirement of independence, but can be dependent. Each of the CRM can also be used to determine the confidence interval of the number of cases.

Calendar time trends of the insulin-dependent diabetes mellitus mortality in Allegheny county, Pennsylvania

This study applied a Cox proportional hazard model to investigate the calendar time trends of insulin-dependent diabetes mellitus (IDDM) mortality. The study population was the IDDM patients who were diagnosed in the period 1965-1979, less than or equal to 19 years of age at diagnosis, and were residents of Allegheny County, PA. The mortality follow-up for each individual was recorded from the diagnosis of IDDM and till 31 December 1990. There were 999 individuals in this study, and 68 deaths (6.8%) occurred during this 26-year investigation period. Overall, for the patients with the same IDDM duration, non-whites were 1.7 times more likely to die than white group; female IDDM patients had a higher risk of death than male IDDM patients (1.27:1); and the risk of mortality increased as the age at diagnosis increased. When controlling for the gender, ethnic groups and age at onset effect, the risk of dying in different calendar years appeared to be a quadratic form. The highest mortality appeared in the late 60s, and the lowest was in the period of 1975-1979. Disappointingly the mortality has begun to rise again in the latest time frame.

Hazardous waste site frequency: use of the capture-recapture method.

This investigation used a two-source capture-recapture method (CRM) for determining ascertainment and undercounts of non-national priority listed hazardous waste sites in the states of Arizona, Maine and Pennsylvania. These findings suggest that ascertainment of hazardous waste sites vary greatly, with some more accurate (i.e., Maine) than others (i.e., Pennsylvania). These data suggest that nontraditional manufacturing states (e.g., Maine) have a higher ascertainment rate than traditional manufacturing states (e.g., Pennsylvania). These results indicate that resources for locating hazardous waste sites should be more heavily allotted to industrialized areas. We suggest that the CRM is a convenient, low cost and effective method for determining (1) the accuracy of previous estimates, and (2) the number of sites in a locale with 95% confidence intervals along with an estimate of the undercount. Findings suggest that estimates of hazardous waste sites should use the CRM to determine and improve accuracy.

Increasing the shelf life of review papers

EDITOR,—Review articles are very important for summarising medical literature. By the time they are published, however, they are two years out of date because of publication delays, and they rapidly become irrelevant because very recent articles are not included. We proposed a cure to this in our paper titled “The death of biomedical journals,” suggesting that a global information server should replace the traditional paper journal system.1 With the global information server, research findings can be presented and …