HbA1c, fasting and 2 h plasma glucose in current, ex- and never-smokers: a meta-analysis.

AIMS/HYPOTHESIS: The relationships between smoking and glycaemic variables have not been well explored. We compared HbA1c, fasting plasma glucose (FPG) and 2 h plasma glucose (2H-PG) in current, ex- and never-smokers. METHODS: This meta-analysis used individual data from 16,886 men and 18,539 women without known diabetes in 12 DETECT-2 consortium studies and in the French Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) and Telecom studies. Means of three glycaemic variables in current, ex- and never-smokers were modelled by linear regression, with study as a random factor. The I (2) statistic was used to evaluate heterogeneity among studies. RESULTS: HbA1c was 0.10% (95% CI 0.08, 0.12) (1.1 mmol/mol [0.9, 1.3]) higher in current smokers and 0.03% (0.01, 0.05) (0.3 mmol/mol [0.1, 0.5]) higher in ex-smokers, compared with never-smokers. For FPG, there was no significant difference between current and never-smokers (-0.004 mmol/l [-0.03, 0.02]) but FPG was higher in ex-smokers (0.12 mmol/l [0.09, 0.14]). In comparison with never-smokers, 2H-PG was lower (-0.44 mmol/l [-0.52, -0.37]) in current smokers, with no difference for ex-smokers (0.02 mmol/l [-0.06, 0.09]). There was a large and unexplained heterogeneity among studies, with I (2) always above 50%; I (2) was little changed after stratification by sex and adjustment for age and BMI. In this study population, current smokers had a prevalence of diabetes that was 1.30% higher as screened by HbA1c and 0.52% lower as screened by 2H-PG, in comparison with never-smokers. CONCLUSION/INTERPRETATION: Across this heterogeneous group of studies, current smokers had a higher HbA1c and lower 2H-PG than never-smokers. This will affect the chances of smokers being diagnosed with diabetes.

Impact of differences in glucose tolerance on the prevalence of a negative insulinogenic index.

OBJECTIVE: To determine the prevalence of a negative insulinogenic index (change in plasma insulin/change in plasma glucose from 0 to 30 min) from an oral glucose tolerance test according to glucose tolerance category. MATERIALS AND METHODS: Data from the San Antonio Heart Study (n=2494), Japanese American Community Diabetes Study (JACDS; n=594) and Genetics of NIDDM Study (n=1519) were examined. Glucose tolerance was defined by ADA criteria. RESULTS: In the combined cohort, the prevalence of a negative insulinogenic index was significantly higher in diabetes 20/616 (3.2%) compared to normal glucose tolerance 43/2667 (1.6%) (p<0.05). Longitudinally, in the JACDS cohort, the prevalence did not change from baseline (3/594; 0.5%) to 5 (4/505; 0.7%) and 10 years (8/426; 1.9%) (p=0.9) and no subject had a repeat negative insulinogenic index. CONCLUSIONS: A negative insulinogenic index occurs at a low prevalence across glucose tolerance categories although more often in diabetes, but without recurrence over time.

Change in visceral adiposity independently predicts a greater risk of developing type 2 diabetes over 10 years in Japanese Americans.

OBJECTIVE: Visceral adiposity is an important risk factor for cardiovascular disease and type 2 diabetes. We sought to determine whether change in intraabdominal fat area (IAF) over time predicts subsequent development of diabetes. RESEARCH DESIGN AND METHODS: We followed up 436 nondiabetic Japanese-American subjects (mean age 51.9 years, mean BMI 24.2 kg/m(2), 54% male) for development of diabetes. We fit a logistic regression model to examine the association over a 10-year follow-up between change in IAF at 5-year follow-up and other fat areas (measured by computed tomography) and development of incident diabetes, adjusted for age, sex, family history of diabetes in a first-degree relative, second-generation versus third-generation Japanese American (Nisei vs. Sansei), baseline IAF, BMI, weight change over time, smoking status, physical activity level, and subcutaneous fat (SCF) depot areas. RESULTS: Cumulative incidence of diabetes was 20.4% at 10 years. Mean change in IAF was 10.9 cm(2). An increase of 1 SD in IAF was associated with a 1.65-fold increase in the odds of diabetes over 10 years (OR = 1.65, 95% CI 1.21-2.25) after adjusting for the above covariates. This association was also independent of changes in thoracic, thigh, and abdominal SCF, as well as change in weight. CONCLUSIONS: We conclude that baseline IAF and accumulation of fat in this area over time are independent predictors of the development of type 2 diabetes in Japanese Americans.

Associations among visceral fat, all-cause mortality, and obesity-related mortality in Japanese Americans.

OBJECTIVE: The study objective was to examine the associations among visceral fat (VF), all-cause mortality, and obesity-related mortality. RESEARCH DESIGN AND METHODS: A total of 733 Japanese Americans were followed for 16.9 years. Hazard ratios (HRs) per interquartile range increase in VF were calculated using time-dependent Cox proportional hazard models censored at age 82 years, with age as the time axis adjusted for sex and smoking. RESULTS: Higher VF was associated with all-cause mortality (HR 1.39 [95% CI 1.11-1.75] 107 deaths) and obesity-related mortality (1.39 [1.04-1.85], 68 deaths from cardiovascular disease, diabetes, or obesity-related cancer). After further adjustment for waist circumference, VF remained significantly associated with all-cause mortality (1.41 [1.04-1.92]) but not with obesity-related mortality. The associations between mortality and VF were not independent of BMI. CONCLUSIONS: VF was associated with all-cause mortality and obesity-related mortality in Japanese Americans. VF did not significantly improve mortality risk assessment beyond that of BMI.

Intra-abdominal fat accumulation is greatest at younger ages in Japanese-American adults.

AIMS: We evaluated whether changes over 10-11 years in weight, subcutaneous abdominal fat (SQAF), and intra-abdominal fat (IAF) differ by age and contrasted age-related adiposity changes by gender. METHODS: This is a prospective cohort study of non-diabetic, Japanese-American men and women aged 34-74 years. IAF and SQAF were measured by CT scan at baseline and 10-11-year follow-up visits. RESULTS: The youngest participants gained the most weight, SQAF and IAF over 10-11 years. Older age at baseline was associated with significantly less change in weight (beta-coefficient: -0.19, 95% CI -0.22, -0.15), SQAF (beta-coefficient: -0.07, 95% CI -0.11, -0.02) and IAF (beta-coefficient: -0.74, 95% CI -1.03, -0.45) that persisted even after adjustments for sex, smoking, caloric intake, adiposity at baseline, and change in physical activity. Age was positively correlated with change in SQAF (beta-coefficient: 0.14, 95% CI 0.10, 0.18) and IAF (beta-coefficient: 0.51, 95% CI 0.21, 0.81) in separate models after further adjustment for weight change. Gender did not alter the associations between adiposity change and age. CONCLUSIONS: Men and women gained the greatest absolute amount of weight, SQAF, and IAF at younger ages; however, older adults with comparable weight changes had relatively greater fat accumulation within IAF and SQAF depots.

Association between obesity and diabetes mellitus in veterans with spinal cord injuries and disorders.

OBJECTIVES: To examine the association between body mass index (BMI) and clinically diagnosed diabetes in veterans with spinal cord injuries and disorders. We also sought to determine whether there is evidence to support a 10% reduction in BMI cut points, which would lower the upper limit of normal BMI from 24.99 to 22.49 kg/m, for persons with spinal cord injuries and disorders. DESIGN: Cross-sectional analysis using clinical data on 1938 male veterans. Prevalence ratios (95% confidence intervals) were calculated using a generalized linear model and adjusted for age, race, tobacco use, and paraplegia/tetraplegia status. RESULTS: Compared with the National Heart Lung Blood Institute normal BMI category (18.5-24.99 kg/m), the prevalence of diabetes was 50% higher (adjusted prevalence ratio: 1.50, 95% CI: 1.11-2.01) in the overweight category (25-29.99 kg/m) and approximately 3-fold higher (for obese classes 1-3, adjusted prevalence ratio: 2.74-3.03) in the obese category (BMI >or= 30 kg/m). Compared with the World Health Organization low-normal category (BMI, 18.5-22.99 kg/m), there was no significant difference in the prevalence of diabetes for those in the high normal weight (BMI, 23-24.99 kg/m) or low overweight (BMI, 25-27.49 kg/m) categories. However, the prevalence of diabetes was 2-fold higher among those in the high overweight category (BMI, 27.5-29.99 kg/m; adjusted prevalence ratio: 2.00, 95% CI: 1.33-2.99). CONCLUSIONS: BMI >or=25 kg/m was associated with significantly higher diabetes prevalence in male veterans with spinal cord injuries and disorders, and this risk was especially pronounced at BMI >or=27.5 kg/m. These findings do not support the need to create spinal cord injuries and disorder-specific BMI definitions of overweight for purposes of determining diabetes risk.

The association between A1C and subclinical cardiovascular disease: the multi-ethnic study of atherosclerosis.

OBJECTIVE: To test the hypothesis that A1C is associated with subclinical cardiovascular disease (CVD) in a population without evident diabetes, after adjusting for traditional CVD risk factors and BMI. RESEARCH DESIGN AND METHODS: This was a cross-sectional study of 5,121 participants without clinically evident CVD or diabetes (fasting glucose > or =7.0 mmol/l or use of diabetes medication), aged 47-86 years, enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA). Measurements included carotid intimal-medial wall thickness (CIMT) and coronary artery calcification (CAC). Results were adjusted for age, sex, ethnicity, smoking, systolic blood pressure, LDL cholesterol, HDL cholesterol, antihypertensive medication use, lipid-lowering medication use, and BMI. RESULTS: Compared with those in the lowest quartile for A1C ([mean +/- SD] 5.0 +/- 0.2%), participants in the highest quartile (6.0 +/- 0.3%) had higher adjusted mean values for common CIMT (0.85 vs. 0.87 mm, P = 0.003) and internal CIMT (1.01 vs. 1.08 mm, P = 0.003). A1C quartile was not associated with prevalence of CAC in the entire cohort (P = 0.27); however, the association was statistically significant in women (adjusted prevalence of CAC in lowest and highest A1C quartiles 37.5 vs. 43.0%, P = 0.01). Among those with some CAC, higher A1C quartile tended to be associated with higher CAC score, but the results were not statistically significant (adjusted P = 0.11). CONCLUSIONS: In this multiethnic cohort, there were small, positive associations between A1C, common CIMT, and internal CIMT in the absence of clinically evident diabetes. An association between higher A1C and CAC prevalence was evident only in women.

The association between birth weight and visceral fat in middle-age adults.

OBJECTIVE: Low birth weight, a proxy for fetal underdevelopment, is associated with increased risk of developing type 2 diabetes during adulthood. Low birth weight is also associated with central obesity, but little is known about the association between birth weight and visceral adiposity. The purpose of this study is to test the hypothesis that lower birth weight is associated with increased amounts of visceral fat in middle-age adults. RESEARCH METHODS AND PROCEDURES: This is an observational study of 91 adults (58 men and 33 women) 40+/-6 years of age (mean+/-standard deviation). Ethnicity was either Japanese American (79%) or non-Hispanic white (21%). Birth weight was obtained from State Departments of Health. Measurements included smoking status, BMI, and visceral (intra-abdominal) fat measured by computed tomography. RESULTS: Visceral fat was not associated with birth weight after adjustment for age, sex, ethnicity, BMI, or smoking status (p=0.76). There was no evidence that the association between birth weight and visceral fat varied by age, sex, or ethnicity. DISCUSSION: We found no evidence that low birth weight is associated with increased visceral fat in middle-age adults.

Association of endothelial lipase gene (LIPG) haplotypes with high-density lipoprotein cholesterol subfractions and apolipoprotein AI plasma levels in Japanese Americans.

The LIPG gene on chromosome 18 encodes for endothelial lipase, a member of the triglyceride lipase family. Mouse models suggest that variation in LIPG influences high-density lipoprotein (HDL) metabolism, but only limited data are available in humans. This study examined associations of LIPG haplotypes, comprising a single nucleotide polymorphism (SNP) in the promoter region (-384A>C), and a nonsynonymous SNP in exon 3 (Thr111Ile or 584C>T), with lipoprotein risk factors in 541 adult Japanese Americans. A marginal association was found between LIPG diplotypes and HDL cholesterol (p=0.045). Stronger associations were seen for HDL3 cholesterol (p=0.005) and Apolipoprotein AI plasma levels (p=0.002). After adjustment for age, gender, smoking and medications, individuals homozygous for the minor allele at both SNPs (*4 haplotype) had a more favorable risk factor profile, compared to other haplotype combinations. No relationship was seen for plasma triglyceride levels or low-density lipoprotein (LDL) size, but the homozygous *4 diplotype was also associated with lower Apolipoprotein B and LDL cholesterol levels (p=0.001 and 0.015, respectively). In conclusion, this community-based family study of Japanese Americans demonstrates that LIPG variants are associated with HDL related risk factors, and may play a role in susceptibility to cardiovascular disease in this population.

Diabetes-related comorbidities in Asian Americans: results of a national health survey.

OBJECTIVE: The aim of this study was to compare the prevalence of diabetes-related comorbidities in Asian Americans to the prevalence in other racial and ethnic groups in the United States using data from the 2001 Behavioral Risk Factor Surveillance System (BRFSS). METHODS: The BRFSS is a population-based telephone survey of the health status and health behaviors of 212,510 Americans aged > or = 18 years in all 50 states, Guam, Puerto Rico, and the U.S. Virgin Islands. In 2001, participants included 196 Asian Americans, 1138 African Americans, 1276 Hispanics, 294 Native Americans, 71 Pacific Islanders, and 7799 non-Hispanic Whites with a self-reported physician diagnosis of diabetes. Comorbidity was determined by self-report. Odds ratios (OR) were adjusted for age, sex, body mass index (BMI) or height and weight, duration of diabetes, smoking, and health-insurance status. RESULTS: The adjusted prevalences of hypercholesterolemia and retinopathy were similar across groups. Relative to Asian Americans, only African Americans were more likely to report hypertension [adjusted OR=2.1, 95% confidence interval (CI)=1.0-4.2, P<.05]. Higher odds of current or past foot ulceration was observed for Hispanics (adjusted OR=2.8, 95% CI=1.2-6.9), Native Americans (adjusted OR=4.2, 95% CI=1.4-12.8), and Pacific Islanders (adjusted OR=7.4, 95% CI=1.3-41.2) compared with Asian Americans. CONCLUSIONS: Among Americans with diabetes, Asian Americans have a prevalence of hypertension, hypercholesterolemia, retinopathy, and foot ulceration that is similar to that in Whites. Asian Americans had a significantly lower prevalence of hypertension than African Americans did and a lower prevalence of foot ulceration than Hispanics, Native Americans, and Pacific Islanders did.

Visceral adiposity is an independent predictor of incident hypertension in Japanese Americans.

BACKGROUND: Visceral adiposity is generally considered to play a key role in the metabolic syndrome. OBJECTIVE: To examine the relationship between directly measured visceral adiposity and the risk for incident hypertension, independent of other adipose depots and fasting plasma insulin levels. DESIGN: Community-based prospective cohort study with 10- to 11-year follow-up. SETTING: King County, Washington. PARTICIPANTS: 300 Japanese Americans with a systolic blood pressure less than 140 mm Hg and a diastolic blood pressure less than 90 mm Hg who were not taking antihypertensive medications, oral hypoglycemic medications, or insulin at study entry. MEASUREMENTS: Abdominal, thoracic, and thigh fat areas were measured by using computed tomography. Total subcutaneous fat area was calculated as the sum of these fat areas excluding the intra-abdominal fat area. Hypertension during follow-up was defined as having a systolic blood pressure of 140 mm Hg or greater, having a diastolic blood pressure of 90 mm Hg or greater, or taking antihypertensive medications. RESULTS: There were 92 incident cases of hypertension during the follow-up period. The intra-abdominal fat area was associated with an increased risk for hypertension. Multiple-adjusted odds ratios of hypertension for quartiles of intra-abdominal fat area (1 = lowest; 4 = highest) were 5.07 (95% CI, 1.75 to 14.73) for quartile 3 and 3.48 (CI, 1.01 to 11.99) for quartile 4 compared with quartile 1 after adjustment for age, sex, fasting plasma insulin level, 2-hour plasma glucose level, body mass index, systolic blood pressure, alcohol consumption, smoking status, and energy expenditure through exercise (P = 0.003 for quadratic trend). The intra-abdominal fat area remained a significant risk factor for hypertension, even after adjustment for total subcutaneous fat area, abdominal subcutaneous fat area, or waist circumference; however, no measure of these fat areas was associated with risk for hypertension in models that contained the intra-abdominal fat area. LIMITATIONS: It is not known whether these results pertain to other ethnic groups. CONCLUSIONS: Greater visceral adiposity increases the risk for hypertension in Japanese Americans.