The objective of this study was to evaluate the cross-sectional association between physical acti... more The objective of this study was to evaluate the cross-sectional association between physical activity and serum IgG antibodies against selected periodontal microorganisms. The study population consisted of 5,611 randomly selected US adults who participated in the National Health and Nutrition Examination Survey (NHANES) III (1988 to 1994), who were 40 years and older with complete IgG antibody data against 19 oral microorganisms. We used cluster analysis to classify the 19 antibody titers into 4 mutually exclusive groups called "Orange-Red," "Red-Green," "Yellow- Orange," and "Orange-Blue," and calculated cluster scores by summing antibody titer z-scores for each of the four groups. Physical activity was evaluated based on reported frequency and intensity of physical activity conducted in the last month. Participants were grouped into three categories: adequately physically active, inadequately physically active, and inactive. The outcomes wer...
International journal of hygiene and environmental health, Jan 22, 2016
Dietary methylmercury intake can occur not only through fish ingestion but also through rice inge... more Dietary methylmercury intake can occur not only through fish ingestion but also through rice ingestion; however, rice does not contain the same beneficial micronutrients as fish. In rural China, where rice is a staple food, associations between prenatal methylmercury exposure (assessed using maternal hair mercury) and impacts on offspring neurodevelopment were investigated. A total of 398 mothers were recruited at parturition at which time a sample of scalp hair was collected. Offspring (n=270, 68%) were assessed at 12 months using the Bayley Scales of Infant Development-II, yielding age-adjusted scores for the Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI). Among 270 mothers, 85% ingested rice daily, 41% never or rarely ingested fish/shellfish and 11% ingested fish/shellfish at least twice/weekly. Maternal hair mercury averaged 0.41μg/g (median: 0.39μg/g, range: 0.079-1.7μg/g). In unadjusted models, offspring neurodevelopment (both MDI and PDI) was inver...
Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies ... more Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies concerning prenatal methylmercury exposure through rice ingestion, yet the health risks are greatest to the developing fetus, and thus should be investigated. Our main objective was to quantify dietary methylmercury intake through rice and fish/shellfish ingestion among pregnant mothers living in southern China, where rice was a staple food and mercury contamination was considered minimal. A total of 398 mothers were recruited at parturition, who donated scalp hair and blood samples. Total mercury and/or methylmercury concentrations were measured in biomarkers, in rice samples from each participant's home, and in fish tissue purchased from local markets. Additional fish/shellfish mercury concentrations were obtained from a literature search. Dietary methylmercury intake during the third trimester was equivalent to the ingestion rate for rice (or fish/shellfish)×the respective methylm...
To determine the prevalence and accuracy of patient-reported provider advice on weight gain, phys... more To determine the prevalence and accuracy of patient-reported provider advice on weight gain, physical activity, and nutrition during prenatal visits and to examine the associations of provider advice with women's behavioral intentions toward weight gain, physical activity, and nutrition. A mixed-methods study design was used to assess patient-report of provider advice and health intentions in women between 20 and 30 weeks gestation (n = 188). Bivariate analyses examined patient-reported provider advice on weight gain, physical activity, and nutrition with women's behavioral intentions. Linear and logistic regression models examined associations of provider weight gain recommendations with women's intended weight gain. Approximately 52 % of women reported provider advice on weight gain, 63 % on physical activity, and 56 % on nutrition. Of those who reported weight gain advice, 79 % cited provider recommendations within the Institute of Medicine guidelines, 9 % below, and ...
The Science of the total environment, Jan 18, 2016
Exposure to arsenic (As) or lead (Pb) has been associated with adverse health outcomes, and high-... more Exposure to arsenic (As) or lead (Pb) has been associated with adverse health outcomes, and high-risk populations can be disproportionately exposed to these metals in soils. The objectives of this study were: to examine if predicted soil As and Pb concentrations at maternal residences of South Carolina (SC) low-income mothers differed based on maternal race (non-Hispanic black versus white), to examine whether differences in predicted residential soil As and Pb concentrations among black and white mothers differed by socioeconomic status (SES), and to examine whether such disparities persisted after controlling for anthropogenic sources of these metals, including direction from, and distance to industrial facilities. Kriged soil As and Pb concentrations were estimated at maternal residences in 11 locations in SC, and models with maternal race and individual and US Census block group level SES measures were examined. US Environmental Protection Agency Toxics Release Inventory (TRI) f...
Adoption has increased in China since 1980 when the government started the one-child policy. Ther... more Adoption has increased in China since 1980 when the government started the one-child policy. There were approximately six million adopted children living in China in 1988. The objective of this study was to compare adopted and biological children in one-child families across a number of measures of physical well-being and school enrollment. The 1992 National Sample Survey on the Situation
The Journals of Gerontology Series A Biological Sciences and Medical Sciences
The purpose of this study is to examine gender differences in functional ability among older adul... more The purpose of this study is to examine gender differences in functional ability among older adults in rural Bangladesh in terms of both self-reported activities of daily living and observed physical performance and to evaluate the extent to which differential reporting by gender contributes to disparities between the two measures. In 1996, the Matlab Health and Socio-Economic Survey collected data on self-reported activities of daily living (ADLs) and observed physical performance for 1,893 men and women aged 50 and older in the Matlab Surveillance area in rural Bangladesh. Gender differences were examined in both self-reported ADLs and physical-performance measures. With physical-performance measures as the gold standard, logistic regression was used to determine how much of the gender difference in the self-reported function was explained by physical-performance ability controlling for age. Older women in this study population consistently had more limitations than men in both self-reported ADLs and observed physical performance. For the same level of observed physical performance, however, older women were more likely than men were to report a higher level of ADL limitation. This reported female health disadvantage varied considerably depending on the nature of the ADLs being examined and the type of scoring system used for the ADLs. One has to be somewhat cautious in interpreting gender differences in self-reported ADL limitations, as they are affected by the gender-specific nature of the reported activity and by gender differences in the perception of response categories.
Evidence of the association between food environment and birth outcomes is limited. This study ai... more Evidence of the association between food environment and birth outcomes is limited. This study aimed to examine the association between individual-level food access measures and birth outcomes. All birth certificates (N = 15,786) from January 1, 2008 to December 31, 2009 in eight counties in South Carolina were included. Access to food was evaluated by the distance to the nearest food store and the number of each type of store within a 1-mile (1.6-km) radius from the women's homes. Birth outcomes included birth weight, low birth weight, gestational age, and preterm birth (PTB). A further distance to the nearest convenience store was associated with higher birth weight and gestational age. Birth weight in areas with two or more convenience stores within a 1-mile (1.6-km) buffer was less [two stores: β = -46.2, 95 % confidence interval (CI) -76.5, -15.9; three or more stores: β = -48.6, 95 % CI -78.8, -18.5], and gestational age was shorter in areas with one or two convenience sto...
We examined differences between China and India in key health and socioeconomic indicators, inclu... more We examined differences between China and India in key health and socioeconomic indicators, including life expectancy, infant and child mortality, non-communicable disease mortality from cancer, cardiovascular diseases (CVD), and diabetes, Human Development Index, Gender Inequality Index, material living conditions, and health expenditure. Data on health and social indicators came from various World Health Organization and United Nations databases on global health and development statistics, including the GLOBOCAN cancer database. Mortality trends were modeled by log-linear regression, and differences in rates and relative risks were tested for statistical significance. Although both countries have made marked improvements, India lags behind China on several key health indicators. Differential rates of mortality decline during 1960-2009 have led to a widening health gap between China and India. In 2009 the infant mortality rate in India was 50 deaths per 1,000 live births, 3 times greater than the rate for China. Sixty-six out of 1,000 Indian children died before reaching their 5th birthday, compared with 19 children in China. China's life expectancy is 9 years longer than India's. Life expectancy at birth in India increased from 42 years in 1960 to 65 years in 2009, while life expectancy in China increased from 47 years in 1960 to 74 years in 2009. Major health concerns for China include high rates of stomach, liver, and lung cancer, CVD, and smoking prevalence. Globally, India ranked 90th and China 102nd in life satisfaction. India's less favorable health profile compared to China is largely attributable to its higher rates of mortality from communicable diseases and maternal and perinatal conditions. Further health gains can be achieved by reducing social inequality, greater investments in human development and health services, and by prevention and control of chronic-disease risks such as hypertension, smoking, obesity, and physical inactivity.
To examine the influence of childhood obesity on the early onset of puberty and sex hormones in g... more To examine the influence of childhood obesity on the early onset of puberty and sex hormones in girls. Healthy girls with different percentages of body fat at baseline (40 obese, 40 normal, and 40 lean) were recruited from three elementary schools in Shenyang, China. These girls (mean age 8.5 years) were also matched by height, school grade, Tanner stage, and family economic status at baseline. Anthropometry, puberty characteristics, and sex hormone concentrations were measured at baseline and at each follow-up visit. The generalized estimating equation model and analysis of variance for repeated measures using a generalized linear model were used to determine the differences in puberty characteristics and sex hormones among three groups. Over 4 years, mean age of breast II onset was earlier among obese girls (8.8 years) than normal girls (9.2 years) and lean girls (9.3 years). The prevalence (%) of early-maturation in the obese, normal, and lean groups was 25.9%, 11.1%, and 7.4%, r...
The purpose of this review was to examine the relationship between exercise dose and reductions i... more The purpose of this review was to examine the relationship between exercise dose and reductions in weight gain during pregnancy in exercise interventions. Systematic literature review. Four electronic research databases (PubMed, Web of Science, CINAHL, and Academic Search Premiere) were used to identify exercise interventions conducted with pregnant women. Eligible articles must have satisfied the following criteria: inclusion of a control condition, exercise as a major intervention component, weight gain measured and reported for each experimental condition, description of exercise dose (frequency, intensity and duration), and utilized an adequate number of control conditions to assess independent effects of exercise on weight gain. The literature search identified 4837 articles. Of these, 174 abstracts were screened and 21 intervention studies (18 exercise-only, 3 exercise/diet) were eligible for review. Only 38% of the interventions achieved statistically significant reductions in gestational weight gain. Successful interventions possessed higher adherence and lower attrition rates and were predominantly conducted among normal weight populations. No clear patterns or consistencies of exercise dose and reductions in weight gain were evident. An exercise dose associated with reductions in weight gain was unquantifiable among these interventions. Adherence and retention rates were strong contributors to the success of exercise interventions on gestational weight gain. It is strongly suggested that future researchers investigate methods to increase adherence and compliance, especially among overweight and obese women, and utilize objective measurement tools to accurately evaluate exercise dose performed by the participants and the impact on body composition and weight gain.
The objective of this study was to evaluate the cross-sectional association between physical acti... more The objective of this study was to evaluate the cross-sectional association between physical activity and serum IgG antibodies against selected periodontal microorganisms. The study population consisted of 5,611 randomly selected US adults who participated in the National Health and Nutrition Examination Survey (NHANES) III (1988 to 1994), who were 40 years and older with complete IgG antibody data against 19 oral microorganisms. We used cluster analysis to classify the 19 antibody titers into 4 mutually exclusive groups called "Orange-Red," "Red-Green," "Yellow- Orange," and "Orange-Blue," and calculated cluster scores by summing antibody titer z-scores for each of the four groups. Physical activity was evaluated based on reported frequency and intensity of physical activity conducted in the last month. Participants were grouped into three categories: adequately physically active, inadequately physically active, and inactive. The outcomes wer...
International journal of hygiene and environmental health, Jan 22, 2016
Dietary methylmercury intake can occur not only through fish ingestion but also through rice inge... more Dietary methylmercury intake can occur not only through fish ingestion but also through rice ingestion; however, rice does not contain the same beneficial micronutrients as fish. In rural China, where rice is a staple food, associations between prenatal methylmercury exposure (assessed using maternal hair mercury) and impacts on offspring neurodevelopment were investigated. A total of 398 mothers were recruited at parturition at which time a sample of scalp hair was collected. Offspring (n=270, 68%) were assessed at 12 months using the Bayley Scales of Infant Development-II, yielding age-adjusted scores for the Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI). Among 270 mothers, 85% ingested rice daily, 41% never or rarely ingested fish/shellfish and 11% ingested fish/shellfish at least twice/weekly. Maternal hair mercury averaged 0.41μg/g (median: 0.39μg/g, range: 0.079-1.7μg/g). In unadjusted models, offspring neurodevelopment (both MDI and PDI) was inver...
Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies ... more Rice ingestion is an important dietary exposure pathway for methylmercury. There are few studies concerning prenatal methylmercury exposure through rice ingestion, yet the health risks are greatest to the developing fetus, and thus should be investigated. Our main objective was to quantify dietary methylmercury intake through rice and fish/shellfish ingestion among pregnant mothers living in southern China, where rice was a staple food and mercury contamination was considered minimal. A total of 398 mothers were recruited at parturition, who donated scalp hair and blood samples. Total mercury and/or methylmercury concentrations were measured in biomarkers, in rice samples from each participant's home, and in fish tissue purchased from local markets. Additional fish/shellfish mercury concentrations were obtained from a literature search. Dietary methylmercury intake during the third trimester was equivalent to the ingestion rate for rice (or fish/shellfish)×the respective methylm...
To determine the prevalence and accuracy of patient-reported provider advice on weight gain, phys... more To determine the prevalence and accuracy of patient-reported provider advice on weight gain, physical activity, and nutrition during prenatal visits and to examine the associations of provider advice with women's behavioral intentions toward weight gain, physical activity, and nutrition. A mixed-methods study design was used to assess patient-report of provider advice and health intentions in women between 20 and 30 weeks gestation (n = 188). Bivariate analyses examined patient-reported provider advice on weight gain, physical activity, and nutrition with women's behavioral intentions. Linear and logistic regression models examined associations of provider weight gain recommendations with women's intended weight gain. Approximately 52 % of women reported provider advice on weight gain, 63 % on physical activity, and 56 % on nutrition. Of those who reported weight gain advice, 79 % cited provider recommendations within the Institute of Medicine guidelines, 9 % below, and ...
The Science of the total environment, Jan 18, 2016
Exposure to arsenic (As) or lead (Pb) has been associated with adverse health outcomes, and high-... more Exposure to arsenic (As) or lead (Pb) has been associated with adverse health outcomes, and high-risk populations can be disproportionately exposed to these metals in soils. The objectives of this study were: to examine if predicted soil As and Pb concentrations at maternal residences of South Carolina (SC) low-income mothers differed based on maternal race (non-Hispanic black versus white), to examine whether differences in predicted residential soil As and Pb concentrations among black and white mothers differed by socioeconomic status (SES), and to examine whether such disparities persisted after controlling for anthropogenic sources of these metals, including direction from, and distance to industrial facilities. Kriged soil As and Pb concentrations were estimated at maternal residences in 11 locations in SC, and models with maternal race and individual and US Census block group level SES measures were examined. US Environmental Protection Agency Toxics Release Inventory (TRI) f...
Adoption has increased in China since 1980 when the government started the one-child policy. Ther... more Adoption has increased in China since 1980 when the government started the one-child policy. There were approximately six million adopted children living in China in 1988. The objective of this study was to compare adopted and biological children in one-child families across a number of measures of physical well-being and school enrollment. The 1992 National Sample Survey on the Situation
The Journals of Gerontology Series A Biological Sciences and Medical Sciences
The purpose of this study is to examine gender differences in functional ability among older adul... more The purpose of this study is to examine gender differences in functional ability among older adults in rural Bangladesh in terms of both self-reported activities of daily living and observed physical performance and to evaluate the extent to which differential reporting by gender contributes to disparities between the two measures. In 1996, the Matlab Health and Socio-Economic Survey collected data on self-reported activities of daily living (ADLs) and observed physical performance for 1,893 men and women aged 50 and older in the Matlab Surveillance area in rural Bangladesh. Gender differences were examined in both self-reported ADLs and physical-performance measures. With physical-performance measures as the gold standard, logistic regression was used to determine how much of the gender difference in the self-reported function was explained by physical-performance ability controlling for age. Older women in this study population consistently had more limitations than men in both self-reported ADLs and observed physical performance. For the same level of observed physical performance, however, older women were more likely than men were to report a higher level of ADL limitation. This reported female health disadvantage varied considerably depending on the nature of the ADLs being examined and the type of scoring system used for the ADLs. One has to be somewhat cautious in interpreting gender differences in self-reported ADL limitations, as they are affected by the gender-specific nature of the reported activity and by gender differences in the perception of response categories.
Evidence of the association between food environment and birth outcomes is limited. This study ai... more Evidence of the association between food environment and birth outcomes is limited. This study aimed to examine the association between individual-level food access measures and birth outcomes. All birth certificates (N = 15,786) from January 1, 2008 to December 31, 2009 in eight counties in South Carolina were included. Access to food was evaluated by the distance to the nearest food store and the number of each type of store within a 1-mile (1.6-km) radius from the women's homes. Birth outcomes included birth weight, low birth weight, gestational age, and preterm birth (PTB). A further distance to the nearest convenience store was associated with higher birth weight and gestational age. Birth weight in areas with two or more convenience stores within a 1-mile (1.6-km) buffer was less [two stores: β = -46.2, 95 % confidence interval (CI) -76.5, -15.9; three or more stores: β = -48.6, 95 % CI -78.8, -18.5], and gestational age was shorter in areas with one or two convenience sto...
We examined differences between China and India in key health and socioeconomic indicators, inclu... more We examined differences between China and India in key health and socioeconomic indicators, including life expectancy, infant and child mortality, non-communicable disease mortality from cancer, cardiovascular diseases (CVD), and diabetes, Human Development Index, Gender Inequality Index, material living conditions, and health expenditure. Data on health and social indicators came from various World Health Organization and United Nations databases on global health and development statistics, including the GLOBOCAN cancer database. Mortality trends were modeled by log-linear regression, and differences in rates and relative risks were tested for statistical significance. Although both countries have made marked improvements, India lags behind China on several key health indicators. Differential rates of mortality decline during 1960-2009 have led to a widening health gap between China and India. In 2009 the infant mortality rate in India was 50 deaths per 1,000 live births, 3 times greater than the rate for China. Sixty-six out of 1,000 Indian children died before reaching their 5th birthday, compared with 19 children in China. China's life expectancy is 9 years longer than India's. Life expectancy at birth in India increased from 42 years in 1960 to 65 years in 2009, while life expectancy in China increased from 47 years in 1960 to 74 years in 2009. Major health concerns for China include high rates of stomach, liver, and lung cancer, CVD, and smoking prevalence. Globally, India ranked 90th and China 102nd in life satisfaction. India's less favorable health profile compared to China is largely attributable to its higher rates of mortality from communicable diseases and maternal and perinatal conditions. Further health gains can be achieved by reducing social inequality, greater investments in human development and health services, and by prevention and control of chronic-disease risks such as hypertension, smoking, obesity, and physical inactivity.
To examine the influence of childhood obesity on the early onset of puberty and sex hormones in g... more To examine the influence of childhood obesity on the early onset of puberty and sex hormones in girls. Healthy girls with different percentages of body fat at baseline (40 obese, 40 normal, and 40 lean) were recruited from three elementary schools in Shenyang, China. These girls (mean age 8.5 years) were also matched by height, school grade, Tanner stage, and family economic status at baseline. Anthropometry, puberty characteristics, and sex hormone concentrations were measured at baseline and at each follow-up visit. The generalized estimating equation model and analysis of variance for repeated measures using a generalized linear model were used to determine the differences in puberty characteristics and sex hormones among three groups. Over 4 years, mean age of breast II onset was earlier among obese girls (8.8 years) than normal girls (9.2 years) and lean girls (9.3 years). The prevalence (%) of early-maturation in the obese, normal, and lean groups was 25.9%, 11.1%, and 7.4%, r...
The purpose of this review was to examine the relationship between exercise dose and reductions i... more The purpose of this review was to examine the relationship between exercise dose and reductions in weight gain during pregnancy in exercise interventions. Systematic literature review. Four electronic research databases (PubMed, Web of Science, CINAHL, and Academic Search Premiere) were used to identify exercise interventions conducted with pregnant women. Eligible articles must have satisfied the following criteria: inclusion of a control condition, exercise as a major intervention component, weight gain measured and reported for each experimental condition, description of exercise dose (frequency, intensity and duration), and utilized an adequate number of control conditions to assess independent effects of exercise on weight gain. The literature search identified 4837 articles. Of these, 174 abstracts were screened and 21 intervention studies (18 exercise-only, 3 exercise/diet) were eligible for review. Only 38% of the interventions achieved statistically significant reductions in gestational weight gain. Successful interventions possessed higher adherence and lower attrition rates and were predominantly conducted among normal weight populations. No clear patterns or consistencies of exercise dose and reductions in weight gain were evident. An exercise dose associated with reductions in weight gain was unquantifiable among these interventions. Adherence and retention rates were strong contributors to the success of exercise interventions on gestational weight gain. It is strongly suggested that future researchers investigate methods to increase adherence and compliance, especially among overweight and obese women, and utilize objective measurement tools to accurately evaluate exercise dose performed by the participants and the impact on body composition and weight gain.
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Papers by Jihong Liu