Abstract
Objective:
To investigate the association of lactation intensity and duration with postpartum diabetes and prediabetes risks among Chinese women with a history of GDM.
Methods:
We included 1260 women with a history of GDM who participated in the whole population’s GDM universal screening survey by using World Health Organization’s criteria. Lactation intensity and lactation duration were collected by a standardized questionnaire. Postpartum diabetes and prediabetes were confirmed by an oral glucose tolerance test.
Results:
During a mean postpartum period of 3.65 years, we identified 114 cases of diabetes and 417 cases of prediabetes. The multivariable-adjusted hazard ratios based on different lactation intensity (exclusive formula, mixed feeding, exclusive lactation) were 1.00, 0.68, 0.45 for diabetes (Ptrend = 0.008), and 1.00, 0.74, and 0.61 for prediabetes (Ptrend = 0.006), respectively. The multivariable-adjusted hazard ratios associated with different lactation duration (none, 0–6 months, 6–12 months, 12–18 months, ≥18 months) were 1.00, 0.66, 0.42, 0.66, and 0.25 for diabetes (Ptrend = 0.013), and 1.00, 0.82, 0.62, 0.67, and 0.63 for prediabetes (Ptrend = 0.021), respectively. A restricted cubic spline curve showed a graded inverse association of lactation duration with the risks of diabetes and prediabetes (Ptrend < 0.001).
Conclusions:
Higher lactation intensity and longer lactation duration were significantly associated with lower risks of postpartum diabetes and prediabetes among Chinese women with a history of GDM.
Keywords: gestational diabetes, lactation, diabetes, prediabetes
Introduction
Women with gestational diabetes (GDM) are well known to suffer great risks of type 2 diabetes and prediabetes in their postpartum life 1. Diabetes is recognized as a major risk factor of cardiovascular diseases, while in recent years, prediabetes is also found to be associated with an increased risk of composite cardiovascular diseases and all-cause mortality 2. Recently, lactation has been considered as potential benefit for maternal postpartum weight retention and glycemic metabolism 3,4. Several studies have found a graded association between lactation duration and the risk of diabetes 5–11. However, self-reported diagnoses of diabetes were used in some of these studies rather than the lab measurement to define the major outcome 5,9. Moreover, few studies have assessed the association of lactation intensity and duration with postpartum diabetes risk among women with GDM, and their results remain inconsistent due to the relatively small sample sizes of women with GDM, few cases of type 2 diabetes 10,11, and short follow-up time 7,11. Evidence of the contribution of lactation to the progression of diabetes and prediabetes in Asian women with GDM is limited. The aim of this study was to investigate the contribution of lactation intensity and duration to the postpartum diabetes and prediabetes among Chinese women with prior GDM in the Tianjin GDM observational study.
Subjects and Methods
Tianjin GDM screening project
Tianjin is the fourth largest city in China with only 30 minutes away from the Capital Beijing by train. There are six central districts in Tianjin with about 4.3 million residents. Since 1999, the Tianjin Women’s and Children’s Health Center launched a universal screening of GDM using WHO’s criteria in all six central districts 12. The screening rate was reported to be >91% between 1999 and 2008 12. We used a 1-hour glucose screening test with 50g glucose load at 26–30 gestational weeks. If the 1-hour glucose level was over 7.8 mmol/L, another 2-h oral glucose tolerance test (OGTT) with 75g glucose load would be performed at the Tianjin Women’s and Children’s Health Center. GDM diagnosis was made as per WHO criteria: a 75-g glucose 2-h OGTT result confirming either diabetes (fasting glucose ≥ 7 mmol/l or 2-hour glucose ≥ 11.1 mmol/l) or impaired glucose tolerance (IGT) (2-hour glucose ≥ 7.8 and < 11.1 mmol/l) 13.
Study samples
Totally 76,325 women were screened from 2005 to 2009, and 4644 women were diagnosed as GDM (Figure 1) 14. We invited these 4644 women with GDM and finally 1263 of them finished the study survey including a questionnaire and an OGTT after August 2009. There were no differences in age, 2 h glucose, fasting glucose, the prevalence of IGT and diabetes at 26–30 gestational weeks, and OGTT tests between those returned and those not returned. Among the 1263 women, 83 were newly diagnosed diabetes using an OGTT and 1180 GDM women received randomization into the intervention group (n=586) and the “usual care” control group (n=594) for another clinical trial. This study was approved by the Human Subjects Committee of the Tianjin Women’s and Children’s Health Center. All the participants provided written informed consent. In the current analysis, 1260 women with GDM were included after excluding 3 GDM women with missing information for lactation duration.
Figure 1.
Flow chart of the study.
Measurements
All study participants filled in a questionnaire about their socio-demographics (age, marital status, education, income, and occupation), history of GDM (fasting and 2-h glucose in the OGTT were measured/available from the central lab in the Tianjin Women’s and Children’s Health Center and treatment of GDM during the pregnancy), family history of diabetes, medical history (hypertension, diabetes, and hypercholesterolemia), pregnancy outcomes (pre-pregnancy weight, weight gain in pregnancy, and number of children), lactation (exclusive formula, mixed or exclusive breast) and lactation duration, dietary habits (a self-administered food frequency questionnaire (FFQ) to measure the frequency and quantity of intake of 33 major food groups and beverages during the past year) 15, alcohol intake, smoking habits, passive smoking, and physical activity (the frequency and duration of leisure time and sedentary activities) at the postpartum baseline survey. They also completed the 3-day 24-hour food records using methods for dietary record collections taught by a dietician. The performance of 3-day 24-hour food records 15, the FFQ 15, and the above questionnaire on assessing physical activity 16,17 have been validated in the China National Nutrition and Health Survey in 2002.
Body weight and height were measured using the standardized protocol by specially trained research doctors. BMI was calculated as the body weight in kilograms divided by the square of the height in meters. Waist circumference was measured at the horizontal level between the inferior costal margin and the iliac crest on the mid-axillary line with women in their standing position. Blood samples were collected in all participants after an overnight fast of at least 12 hours. Participants without a self-reported history of diabetes were given a standard 75-g glucose OGTT test. Plasma glucose was measured on an automatic analyzer (Toshiba TBA-120FR, Japan).
Diagnosis of postpartum diabetes and prediabetes
We used the American Diabetes Association (ADA)’s criteria 18 for the diagnosis of diabetes and prediabetes. Diabetes was defined as fasting glucose ≥ 7.0 mmol/L, and/or 2-h glucose ≥ 11.1 mmol/L. Prediabetes was defined as either impaired fasting glucose (fasting glucose ≥ 5.6 mmol/L and < 7.0 mmol/L) or IGT (2-h glucose ≥ 7.8 mmol/L and < 11.1 mmol/L). Those using antidiabetic drugs in the examination were also included into the type 2 diabetes cases.
Statistical analysis
One-way ANOVA and chi-square test were used to compare the mean levels of continuous variables and the prevalence of categorical variables among women with different glycemic status. Cox proportional hazard regression analysis was used to assess risks of postpartum diabetes and prediabetes in women with different lactation intensity and duration. We used the restricted cubic spline nested in time-dependent Cox models to test whether there was a dose-response or nonlinear association of lactation duration as a continuous variable with the risks of diabetes and prediabetes. All analyses were adjusted for pregnant age (Model 1), and then for education, family income, family history of diabetes, treatment of GDM, smoking, passive smoking, alcohol drinking, leisure-time physical activity, sleeping time, dietary fiber, sweetened beverage drinking, energy intakes of fat, protein, and carbohydrate, and pre-pregnancy BMI (Model 2), and further for 2-hour glucose during pregnancy (Model 3). P<0.05 was considered statistically significant. All statistical analyses were performed by IBM SPSS Statistics for Windows, version 24.0 (IBM Corp., Armonk, N.Y., USA), and SAS for Windows, version 9.3 (SAS Institute, Inc, Cary, NC).
Results
The flow diagram of the study was presented in Figure 1. General characteristics of the study participants were presented in Table 1. GDM women who were diagnosed prediabetes and diabetes during postpartum period had significantly higher pre-pregnancy BMI, fasting and 2-hour glucose during pregnancy, postpartum fasting glucose, postpartum 2-hour glucose, postpartum HbA1c, lower education and family income, and were more often with a family history of diabetes compared with GDM women with a normal glucose.
Table 1.
Characteristics of women with gestational diabetes by different glycemic status confirmed by postpartum oral glucose tolerance test
| Normal glucose | Pre-diabetes | Diabetes | P value † | |
|---|---|---|---|---|
| No. of participants | 729 | 417 | 114 | |
| Age at delivery, years | 30.0±3.31 | 30.4±3.81 | 29.7±3.55 | 0.637 |
| Age at baseline, years | 33.5±3.93 | 34.5±4.50 | 32.8±3.63 | 0.410 |
| Pre-pregnancy body mass index, kg/m2 | 22.4±2.98 | 23.7±3.37 | 25.6±3.64 | <0.001 |
| Duration after delivery, years | 3.50±2.10 | 4.08±2.37 | 3.04±1.53 | 0.411 |
| Weight gain during pregnancy, kg | 17.2±5.85 | 16.5±6.07 | 15.3±6.28 | 0.001 |
| Fasting glucose during pregnancy, mmol/l | 5.17±0.69 | 5.44±0.81 | 5.93±0.81 | <0.001 |
| 2-hour glucose during pregnancy, mmol/l | 8.99±1.14 | 9.12±1.18 | 10.3±1.75 | <0.001 |
| Treatment of gestational diabetes | ||||
| Daily self-monitoring of blood glucose, % | 14.0 | 14.9 | 23.7 | 0.020 |
| Diet control or physical activity only, % | 40.6 | 36.0 | 30.7 | 0.449 |
| Diet control + physical activity, % | 45.4 | 48.2 | 53.5 | 0.030 |
| Insulin, % | 2.61 | 3.12 | 21.1 | <0.001 |
| Lactation intensity | 0.007 | |||
| Exclusive formula, % | 11.9 | 15.1 | 22.8 | |
| Mixed feeding, % | 43.6 | 42.7 | 41.2 | |
| Exclusive lactation, % | 44.4 | 42.2 | 36.0 | |
| Lactation duration, months | 9.05±6.16 | 8.43±6.12 | 7.60±6.45 | 0.010 |
| Body mass index, kg/m2 | 23.1±3.35 | 25.4±4.01 | 27.7±4.27 | <0.001 |
| Waist circumference, cm | 77.9±8.15 | 82.9±9.65 | 89.1±9.44 | <0.001 |
| Fasting glucose postpartum, mmol/l | 5.00±0.37 | 5.67±0.54 | 7.35±1.94 | <0.001 |
| 2-hour glucose postpartum, mmol/l | 5.89±0.98 | 7.87±1.63 | 13.5±3.01 | <0.001 |
| HbA1c postpartum, mmol/mol | 36±6 | 38±6 | 50±12 | <0.001 |
| HbA1c postoartum, % | 5.5±0.6 | 5.7±0.5 | 6.8±1.1 | <0.001 |
| Education, % | 0.001 | |||
| <13 years | 19.9 | 25.2 | 29.8 | |
| 13–16 years | 71.3 | 68.6 | 66.7 | |
| ≥16 years | 8.8 | 6.2 | 3.5 | |
| Family income, % | 0.003 | |||
| <5000 yuan per month | 24.7 | 29.0 | 40.4 | |
| 5000–8000 yuan per month | 38.7 | 34.1 | 35.1 | |
| ≥8000 yuan per month | 36.6 | 36.9 | 24.6 | |
| Family history of diabetes, % | 31.6 | 37.4 | 56.1 | <0.001 |
| Current smoking, % | 2.6 | 2.2 | 2.6 | 0.810 |
| Passive smoking, % | 42.8 | 42.0 | 36.0 | 0.248 |
| Current alcohol drinkers, % | 26.2 | 28.1 | 25.4 | 0.809 |
| Leisure time physical activity, % | 0.116 | |||
| 0 min per day | 70.6 | 72.2 | 78.9 | |
| 1–29 min per day | 26.3 | 24.7 | 19.3 | |
| ≥30 min per day | 3 | 3.1 | 1.8 | |
| Sleeping time, hours/day | 7.71±1.00 | 7.64±1.02 | 7.79±1.09 | 0.859 |
| Energy consumption, kcal/day * | 1673±416 | 1754±455 | 1714±427 | 0.020 |
| Fiber, g/day | 12.1±4.39 | 12.7±4.95 | 12.4±4.74 | 0.091 |
| Fat, % energy | 33.0±5.99 | 33.2±6.28 | 33.3±6.32 | 0.567 |
| Carbohydrate, % energy | 50.3±6.98 | 50.1±7.12 | 50.3±7.12 | 0.715 |
| Protein, % energy | 16.7±2.71 | 16.7±2.70 | 16.4±2.42 | 0.671 |
| Sweetened beverage drink, % | 77.2 | 80.6 | 74.6 | 0.813 |
Dietary intakes are assessed by 3-day 24-h food records
P for trend across different glycemic status.
During a mean 3.65±2.17 years postpartum, we confirmed 114 cases of diabetes and 417 cases of prediabetes by OGTT. There were inverse associations of lactation intensity and duration with the risks of postpartum diabetes and prediabetes (Table 2). The multivariable-adjusted (age, education, family income, family history of diabetes, treatment of GDM, smoking, passive smoking, alcohol drinking, leisure-time physical activity, sleeping time, dietary fiber, sweetened beverage drinking, energy intakes of fat, protein, and carbohydrate, pre-pregnancy BMI, and 2-hour glucose during pregnancy) hazard ratios based on different lactation intensity (exclusive formula, mixed feeding, exclusive lactation) were 1.00, 0.68 (95% confidence interval [CI] 0.41–1.15), 0.45 (95% CI 0.27–0.75) for diabetes (P for trend = 0.008), and 1.00, 0.74 (95% CI 0.55–1.00), and 0.61 (95% CI 0.46–0.84) for prediabetes (P for trend = 0.006), respectively.
Table 2.
Hazard ratios of diabetes and pre-diabetes by lactation intensity and duration
| No. of patients | No. of cases | Person-years | Hazard ratios (95% confidence intervals) | |||
|---|---|---|---|---|---|---|
| Model 1 | Model 2 | Model 3 | ||||
| Diabetes | 1260 | 114 | 4595 | |||
| Lactation intensity | ||||||
| Exclusive formula | 176 | 26 | 600 | 1.00 | 1.00 | 1.00 |
| Mixed feeding | 543 | 47 | 1956 | 0.60 (0.37−0.97) | 0.58 (0.35−0.96) | 0.68 (0.41−1.15) |
| Exclusive lactation | 541 | 41 | 2039 | 0.43 (0.26−0.71) | 0.39 (0.23−0.64) | 0.45 (0.27−0.75) |
| P for trend | 0.004 | 0.001 | 0.008 | |||
| Lactation duration (months) | ||||||
| None | 176 | 26 | 600 | 1.00 | 1.00 | 1.00 |
| 0–6 | 249 | 24 | 833 | 0.70 (0.40−1.22) | 0.64 (0.36−1.14) | 0.66 (0.37−1.19) |
| 6–12 | 342 | 20 | 1350 | 0.34 (0.19−0.60) | 0.39 (0.21−0.71) | 0.42 (0.22−0.78) |
| 12–18 | 377 | 39 | 1404 | 0.64 (0.39−1.05) | 0.53 (0.32−0.89) | 0.66 (0.39−1.12) |
| >18 | 116 | 5 | 408 | 0.28 (0.11−0.72) | 0.19 (0.07−0.52) | 0.25 (0.09−0.65) |
| P for trend | 0.002 | 0.002 | 0.013 | |||
| Lactation duration as a continuous variable (1 month increase) | 0.96 (0.93−0.99) | 0.95 (0.92−0.98) | 0.96 (0.93−0.98) | |||
| Pre-diabetes | 1146 | 417 | 4248 | |||
| Lactation intensity | ||||||
| Exclusive formula | 150 | 63 | 510 | 1.00 | 1.00 | 1.00 |
| Mixed | 496 | 178 | 1829 | 0.67 (0.50−0.90) | 0.73 (0.55−0.98) | 0.74 (0.55−1.00) |
| Exclusive lactation | 500 | 176 | 1909 | 0.57 (0.43−0.76) | 0.62 (0.46−0.83) | 0.61 (0.46−0.84) |
| P for trend | 0.001 | 0.006 | 0.006 | |||
| Lactation duration (months) | ||||||
| None | 150 | 63 | 510 | 1.00 | 1.00 | 1.00 |
| 1–6 | 225 | 83 | 766 | 0.77 (0.55–1.07) | 0.83 (0.59−1.16) | 0.82 (0.59−1.15) |
| 6–12 | 322 | 114 | 1296 | 0.55 (0.40–0.75) | 0.61 (0.45−0.84) | 0.62 (0.45−0.85) |
| 12–18 | 338 | 122 | 1283 | 0.60 (0.44–0.82) | 0.65 (0.48−0.89) | 0.67 (0.49−0.91) |
| >18 | 111 | 35 | 393 | 0.63 (0.42–0.96) | 0.62 (0.41−0.95) | 0.63 (0.41−0.96) |
| P for trend | 0.001 | 0.014 | 0.021 | |||
| Lactation duration as a continuous variable (1 month increase) | 0.98 (0.96–0.99) | 0.98 (0.96−0.99) | 0.97 (0.96−0.99) | |||
Model 1 adjusted for age; Model 2 adjusted for age, pre-pregnancy body mass index, education, family income, family history of diabetes, treatment of gestational diabetes, current smoking, passive smoking, current alcohol drinking, leisure time physical activity, sleeping time, sweetened beverage drinking, energy intakes, fiber, fat, protein and carbohydrate intakes; Model 3 adjusted for variables in Model 2 and also 2-hour glucose during pregnancy.
The multivariable-adjusted hazard ratios associated with different lactation duration (none, 0–6 months, 6–12 months, 12–18 months, ≥18 months) were 1.00, 0.66, 0.42, 0.66, and 0.25 for diabetes (P for trend = 0.013), and 1.00, 0.82, 0.62, 0.67, and 0.63 for prediabetes (P for trend = 0.021), respectively. When lactation duration was considered as a continuous variable, multivariable-adjusted hazard ratios for each 1-month increase in lactation duration were 0.95 (95% CI 0.92–0.98) for postpartum diabetes, and 0.98 (95% CI 0.96–0.99) for postpartum prediabetes.
When lactation duration was considered as a continuous variable by using restricted cubic splines, a graded inverse association of lactation duration with the risks of diabetes and prediabetes was observed (P for trend <0.001) (Figure 2). The relatively lower risk of diabetes occurred when lactation duration was found around 6 months, then the risk slightly increased and finally became much lower when lactation duration was over 18 months. This curve trend was consistent with the findings in Table 2 when lactation duration was considered as a categorical variable. Similar results could also be found in the analysis regarding the risk of prediabetes.
Figure 2.
Hazard ratios of diabetes and prediabetes by lactation duration among women with GDM. Adjustments were made for age, pre-pregnancy body mass index, education, family income, family history of diabetes, treatment of GDM, current smoking, passive smoking, current alcohol drinking, leisure time physical activity, sleeping time, dietary fiber, sweetened beverage drinking, energy intakes of fat, protein, and carbohydrate, and 2-hour glucose during pregnancy.
Discussion
Our study found that exclusive breast feeding was related to 55% and 39% lower risks of postpartum diabetes and prediabetes respectively when compared with exclusive formula feeding in Chinese women with prior GDM. This study indicated an inverse and graded association of lactation duration with the risks of diabetes and prediabetes among women with prior GDM. Our findings were strengthened and more plausible due to the accurate diagnosis of postpartum diabetes and prediabetes by performing an OGTT and the multivariable adjustments for pre-pregnancy BMI, treatment of GDM, 2-hour glucose during pregnancy, lifestyle and sociodemographic factors.
Findings from the present study on the inverse association are in general consistent with those from previous studies. For instance, in the SWIFT (Study of Women, Infant Feeding and Type 2 Diabetes After GDM Pregnancy SWIFT) study including 959 women with GDM found an inverse association of lactation intensity (exclusive formula, mixed formula, and exclusive lactation) and lactation duration with the risk of postpartum 2-year diabetes 7. One recent meta-analysis 4 including the SWIFT 7, another prospective cohort 10, 2 cross-sectional studies 19,20 and 1 retrospective cohort study 21 has indicated that longer lactation for more than 4 to 12 weeks postpartum compared with shorter lactation among women with GDM showed a reduced risk of type 2 diabetes at postpartum 2 years (odd ratio 0.56, 95% CI 0.35–0.89), and more than 5 years (odd ratio 0.22, 95% CI 0.13–0.36), but not within 12 weeks postpartum (odd ratio 0.77, 95% CI 0.01–55.9). However, these previous studies are largely limited by small sample sizes of women with GDM (except SWIFT study) and few cases of type 2 diabetes (n=12–113) with limited power, by the cross-sectional design 19,20, short follow-up time (2 studies within 12 weeks postpartum 19,20, and 1 study at 2 years postpartum 7), insufficient multivariable adjustment for major diabetes risk factors 10,19–21, and incomplete ascertainment of diabetes by self-reported records 5.
The association of lactation intensity and duration with type 2 diabetes risk has been assessed in the western population. Due to one-child policy from 1979 to 2015 in China 22,23, no parity bias is caused and considered in the present analysis. The present study with large sample sizes of women with GDM, long follow-up, and enough cases of postpartum diabetes and prediabetes identified by an OGTT during follow-up demonstrated that exclusive breast feeding compared with exclusive formula feeding reduced 61% risk of postpartum diabetes after adjusting major diabetes risk factors. In addition, we found an inverse and graded association of lactation duration with the risk of postpartum diabetes among women with prior GDM.
The present study was the first to assess the association of lactation intensity and lactation duration with the long-term risk of postpartum prediabetes identified by an OGTT among Chinese women with prior GDM. Although most women with GDM return to a normal glucose status after delivery, about 30% women with GDM develop prediabetes during early postpartum 14. Prediabetes has been reported associated with an increased risk of cardiovascular and renal diseases 2,24. We have indicated a 39% reduction of prediabetes risk among women with exclusive lactation versus exclusive formula. We also found an inverse and graded association of lactation duration with the risk of postpartum prediabetes among women with prior GDM. It is noteworthy that lactation of over six months should be the first priority of childbearing in women with prior GDM, which will be beneficial for both their children and themselves.
Our findings manifested the WHO recommendation that infants should be exclusively lactated in the first six months 25. However, in a national survey of breastfeeding rate in China, the crude breastfeeding rate of infants under 6 months was reported to be only 20.7% 26. Policies and national supports regarding the extension of the lactation duration among parous women especially those with prior GDM are needed to relieve the increasing healthcare burden of diabetes and its complications in China.
Several mechanisms are plausible to explain the lower risks of diabetes and prediabetes associated with lactation. Lactation was reported to reduce the postpartum weight retention in several studies 27,28, and weight retention was considered to be one of the risk factors of postpartum diabetes 29. Meanwhile, prolactin may also play an important role in reducing the risks of diabetes and prediabetes postpartum. Moderately increasing level of prolactin during pregnancy and later lactation has been proven to be beneficial to β cell function and hepatic insulin resistance 30. Another cross-sectional study also found that increasing prolactin level was associated with reduced risks for both diabetes and prediabetes 31. Further prospective studies are warranted to see whether there is a causal relationship between prolactin and diabetes and prediabetes.
Strengths of this study include the relatively large sample size of women with prior GDM. In addition, diagnoses of GDM and postpartum diabetes and prediabetes were based on an OGTT. However, we did not use HbA1c as one of the diagnostic criteria of diabetes or prediabetes postpartum mainly because several studies showed that using HbA1c in isolation to predict glucose tolerance in women with a history of GDM was limited due to its poor sensitivity, which may cause missing diagnosis of incident diabetes or prediabetes 32,33. One limitation of this study is the return rate of the initial invitation with only 27% of all GDM women, which may cause the selection bias. Second, we have no data on 1 h glucose and 3 h glucose during pregnancy since we used the WHO’s diagnostic criteria for GDM. Third, lactation intensity and duration were based on self-reported data which might be influenced by multiple factors, such as pre-pregnancy obesity, and treatment during pregnancy. However, we have controlled all these factors and other major confounding factors in the multivariable-adjusted analyses. Finally, due to the retrospective design of this study, the causal relationship between lactation and hyperglycemia could not be well clarified. Further prospective studies were necessary.
In conclusion, among parous women with prior GDM, exclusive lactation was associated with significantly reduced risks of postpartum diabetes and prediabetes. Findings from Chinese women along with those in other population supported the potential of lactation in lowering risks of type 2 diabetes. Lactation of over 6 months may be a practical, low-cost intervention during an early postpartum period to prevent diabetes and prediabetes among women with prior GDM.
Acknowledgements:
We would like to appreciate all families for participating in the Tianjin Gestational Diabetes Mellitus Prevention Program.
Funding: This study is supported by the grant from European Foundation for the Study of Diabetes (EFSD)/Chinese Diabetes Society (CDS)/Lilly programme for Collaborative Research between China and Europe, Tianjin Women’s and Children’s Health Center, and Tianjin Public Health Bureau. Dr. Hu was partly supported by the grant from the National Institute of Diabetes and Digestive and Kidney Diseases (R01DK100790) and the National Institute of General Medical Sciences (U54GM104940) of the National Institutes of Health.
Role of the funder/sponsor: The funding sources had no role in the design and conduct of the study, collection, management, analysis, and interpretation of the data, preparation, review, or approval of the manuscript, and decision to submit the manuscript for publication.
Footnotes
Conflicts of interest disclosures: The authors have nothing to disclose.
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