Prevalence of metabolic syndrome and common metabolic components in high altitude farmers and herdsmen at 3700 m in Tibet

Prevalence of metabolic syndrome and its components according to altitude levels: a systematic review and meta-analysis

Metabolic syndrome has a multifactorial origin; however, epidemiological data correspond to populations located at sea level. It has been reported that the altitude can affected the prevalence due to physiological changes. The aim of this study is to show the global prevalence of metabolic syndrome at altitude and its components. We use four databases, all studies published up to November 2023. The prevalences from studies were meta-analyzed using a random-effects model. To assess sources of heterogeneity, subgroup analyses were performed. We included 28 studies. The number of participants was 29 195. The prevalence of metabolic syndrome was 30.3% (95% CI 22.8-38.4%). According to the altitude level, at 1500-2500 was 36.5%, 2500-3500 (21.8%), and > 3500 (30.9%), also it was higher in women (35.5%) that men (26.8%). It was observed that there is an inverse relationship between higher altitude and the prevalence of metabolic syndrome. Among its components, abdominal obesity and low HDL were present in more than 40.0%, while high blood pressure, high triglycerides and impaired glucose were present in less than 30.0%. We recommend that our results be considered for future research in populations living at altitude since they have different characteristics from populations at sea level.

Establishment of a Risk Prediction Model for Metabolic Syndrome in High Altitude Areas in Qinghai Province, China: A Cross-Sectional Study

Purpose

The prevalence of metabolic syndrome (MetS) is increasing worldwide, and early prediction of MetS risk is highly beneficial for health outcomes. This study aimed to develop and validate a nomogram to predict MetS risk in Qinghai Province, China, and it provides a methodological reference for MetS prevention and control in Qinghai Province, China.

Patients and Methods

A total of 3073 participants living between 1900 and 3710 meters above sea level in Qinghai Province participated in this study between March 2014 and March 2016. We omitted 12 subjects who were missing diagnostic component data for MetS, ultimately resulting in 3061 research subjects, 70% of the subjects were assigned randomly to the training set, and the remaining subjects were assigned to the validation set. The least absolute shrinkage and selection operator (LASSO) regression analysis method was used for variable selection via running cyclic coordinate descent with 10-fold cross-validation. Multivariable logistic regression was then performed to develop a predictive model and nomogram. The receiver operating characteristic (ROC) curves was used for model evaluation, and calibration plot and decision curve analysis (DCA) were used for model validation.

Results

Of 24 variables studied, 6 risk predictors were identified by LASSO regression analysis: hyperlipidaemia, hyperglycemia, abdominal obesity, systolic blood pressure (SBP), diastolic blood pressure (DBP), and body mass index (BMI). A prediction model including these 6 risk factors was constructed and displayed good predictability with an area under the ROC curve of 0.914 for the training set and 0.930 for the validation set. DCA revealed that if the threshold probability of MetS is less than 82%, the application of this nomogram is more beneficial than both the treat-all or treat-none strategies.

Conclusion

The nomogram developed in our study demonstrated strong discriminative power and clinical applicability, making it a valuable reference for meets prevention and control in the plateau areas of Qinghai Province.

Population Pharmacokinetics of Atorvastatin in High-Altitude and Plain Patients with Hyperlipidemic

The pharmacokinetic (PK) characteristics of drugs were altered under high-altitude hypoxia. We aim to describe the population PK of atorvastatin (ATV) to identify patient characteristics that are predictive of variability in the PK parameters of the ATV and investigate the effects of high-altitude hypoxia on the blood concentration of ATV in patients with hyperlipidemia. A total of 160 plasma concentrations were collected from 40 patients with hyperlipidemia in plateau areas and 40 in plain areas. The population pharmacokinetic model of patients with hyperlipidemia in plateau and plain areas of China was established by a nonlinear mixed-effects model. The PK of ATV were described by a 1-compartment model with first-order elimination. The main PK parameters of ATV were the first-order absorption rate (0.76 hour-1 fixed); clearance (174.22 L/h) and apparent volume of distribution (1119.62 L). The values of area and age were identified as significant covariates for the clearance, area, age, and urea for the volume of distribution. The steady-state peak concentration in the plateau area was higher than that in the plain area. This study may suggest dose reduction is necessary for patients with hyperlipidemia in high altitudes.

Rate and risk factors of metabolic components and component combinations according to hypertension status in Tibetans in a cross-sectional study

To estimate the prevalence of metabolic syndrome (MS) and metabolic components and their associated factors and component combinations according to hypertension status in Tibetans living at high altitude. Multistage sampling of 1473 participants (799 hypertensive patients and 674 normotensive subjects). MS prevalence and the number of metabolic components ≥ 3 were significantly higher in the hypertensive than normotensives. In hypertensive patients, the most common component was central obesity and it combined with: high blood pressure, in those with 2 risk factors, plus fasting hyperglycemia, in those with 3 risk factors, and high triglyceride, in those with 4 risk factors. In normotensive subjects, the most common single component was low high-density-lipoprotein cholesterol, and most component combination included central obesity and hyperglycemia in those with 2 risk factors, plus high blood pressure in those with 3 risk factors, and high triglycerides in those with 4 risk factors. Body mass index and female both were associated with increased possibilities of MS in hypertensive and normotensive participants. Low incoming, and high educational levels were associated with an elevated probability of MS in normotensive Tibetans also. The priority of prevention from cardiovascular diseases by targeting metabolic components in the hypertensive was different from normotensives. Different MS components had various lifestyle and socioeconomic factors.

The association between altitude and the prevalence of hypertension among permanent highlanders

Hypertension (HTN) is a growing contributor to the global disease burden, and it is prevalent among people living at high altitudes (H-ALTs). This study aimed to explore the relationship between altitude and the prevalence of HTN among inhabitants living at H-ALTs. We searched electronic databases, including PubMed, Embase, and Web of Science, up to April 30, 2022. The quality of included studies was assessed using the Joanna Briggs Institute (JBI) checklist for prevalence studies. A total of 1273 articles were screened, and 32 studies (86,487 participants) were eligible for further analyses. The pooled prevalence among highlanders was 28.7%. General additive model (GAM)-based meta-regression analysis was conducted to explore the association between altitude and the prevalence of HTN. A curve-shaped line was found between altitude and the prevalence of HTN (β = 0.998, p = 0.039) after adjusting for factors including publication year, sample size, age, sex, ethnic group, body mass index (BMI), smoking and alcohol consumption. The turning point was observed at 3300 m. The predictive parameter indicated that the smoothness and goodness of model fit were good (GCV = 0.014, R² = 0.60, respectively). The findings may provide clues for further mechanistic studies that can improve HTN prevention among highlanders.

Prevalence, Management, and Associated Factors of Obesity, Hypertension, and Diabetes in Tibetan Population Compared with China Overall

Tibetans’ life expectancy lags behind China’s average. Obesity and noncommunicable diseases (NCDs) contribute to health disparity, but NCD patterns among Tibetans are unknown. To examine the prevalence, management, and associated factors for obesity, hypertension, and diabetes among Tibetans, compared with China’s average, we systematically searched PubMed and China National Knowledge Infrastructure databases for studies between January 2010 and April 2021. Thirty-nine studies were included for systematic review, among thirty-seven that qualified for meta-analysis, with 115,403 participants. Pooled prevalence was 47.9% (95% CI 38.0–57.8) for overweight/obesity among adults (BMI ≥ 24 kg/m²) and 15.4% (13.7–17.2) among children using Chinese criteria, which are lower than the national rates of 51.2% and 19.0%, respectively. The estimate for hypertension (31.4% [27.1–35.7]) exceeded China’s average (27.5%), while diabetes (7.5% [5.2–9.8]) was lower than average (11.9%). Men had a higher prevalence of the three conditions than women. Residents in urban areas, rural areas, and Buddhist institutes had monotonically decreased prevalence in hypertension and diabetes. Awareness, treatment, and control rates for hypertension and diabetes were lower than China’s average. Urban residence and high altitude were consistent risk factors for hypertension. Limited studies investigated factors for diabetes, yet none exist for obesity. Tibetans have high burdens of obesity and hypertension. Representative and longitudinal studies are needed for tailored interventions. There are considerable variations in study design, study sample selection, and data-analysis methods, as well as estimates of reviewed studies.

Diagnostic Criteria for Metabolic Syndrome in High-Altitude Regions: A Systematic Review

Background and Objectives: Metabolic syndrome (MS) has many risk factors that are important to investigate in populations living at sea level and in high-altitude geographic regions. The aim was to identify the components of MS that cross-sectional studies use to assess in adult populations residing in high-altitude regions. Materials and Methods: A systematic review study was conducted. The Pubmed database was used. The search for original articles (cross-sectional) was performed from January 2013 to December 2020. The procedure was carried out by two researchers. The keywords used were metabolic syndrome, adults, and altitude regions. The search strategy considered the components of the PICOS tool. Results: Ten cross-sectional studies were identified in the Pubmed database from 2014 to 2020. Altitude levels varied between countries and regions, from 2060 to 4900 m above sea level. Three studies were conducted in both China and Peru, two studies in Ecuador, and one in Bolivia and India. The age ranges studied were from 18 to ~80 years of age, approximately. The components used to assess MS in most studies (between 9 to 10 studies) were body mass index (BMI), waist circumference (WC), blood pressure (BP), triglycerides (TG), high-density lipoproteins (HDL) and serum glucose (SG). Conclusions: This systematic review verified that the most commonly used domains in adult populations in various moderate- and high-altitude regions of the world are BMI, WC, BP, TG, HDL, and SG. These results suggest that in order to evaluate and/or investigate MS in subjects residing in high-altitude populations, at least four diagnostic domains should be considered in their protocols.

Association between hyperuricemia and metabolic syndrome: A cross-sectional study in Tibetan adults on the Tibetan plateau

PURPOSE

This study aimed to assess the relationship of serum uric acid with metabolic syndrome and its components in Tibetan adults on the Tibetan plateau.

METHODS

A total of 307 participants were enrolled in this study and biochemical parameters including serum uric acid, fasting plasma glucose, white blood cell, lymphocyte count, mononuclear cells, alanine aminotransferase, aspartate aminotransferase, creatinine, and lipid profile were analyzed using standard methods. The IDF criteria were applied to define metabolic syndrome. The association of serum uric acid with metabolic syndrome and its components was evaluated by multivariable logistic regression models.

RESULTS

The overall prevalence of metabolic syndrome was 17.3% (53/307) with 19.6% (31/158) in females and 14.8% (22/149) in male participants. The prevalence of hyperuricemia was 40.7% (125/307) with significant differences between the male (53.7%,80/149) and female (28.5%,45/158) groups. In regression analysis, we observed that the risk of MetS was higher in participants in the hyperuricemia group (adjusted OR, 4.01; 95% CI, 2.02~7.99) compared with those in the normouricemia group. After adjusting for all confounding factors, a 9% higher risk of MetS could be shown in participants with SUA increased per 10umol/L (adjusted OR, 1.09; 95% CI, 1.04~1.14). These relationships were not affected by sex or age (p >0.05). After adjusting for the confounding factors, hyperuricemia is positively associated with abdominal obesity (adjusted OR, 2.53; 95% CI, 1.41~4.53), elevated blood pressure (adjusted OR, 2.61; 95% CI, 1.37~4.97), and elevated triglycerides(adjusted OR, 2.47; 95% CI, 1.09~5.57).

CONCLUSIONS

In our study, hyperuricemia is significantly associated with the prevalence of metabolic syndrome and part of its components, and these relationships are not affected by sex or age. Given the high prevalence of MetS and hyperuricemia among Tibetan adults, more studies are required to explore the role of SUA in the pathogenesis of MetS.

Are the tribal highlanders protected from hypertension? A meta-analysis on prevalence of hypertension among high altitude tribal population of India

Background

The so-called protected tribal population are also facing burden of noncommunicable diseases. The high altitude tribes are thought to be genetically and environmentally protected from hypertension (HTN) like diseases.

Objective

The objective is to estimate the prevalence of HTN among tribes residing at high altitudes (>6000 feet above sea level) of India.

Methods

The meta-analysis was undertaken during March to August 2018. National Library of Medicine's PubMed database, and Google scholar were comprehensively searched including search terms such as "blood pressure, hypertension and prevalence" combined with "tribal, tribes, high altitude, India." Articles on the prevalence of HTN were searched first and then were segregated on the basis of high altitude (>6000 ft).

Results

Initially, 69 references and a total of 16 abstracts were screened. After applying the inclusion and exclusion criteria on 16, eight studies were included. Meta-analysis of the prevalence of selected studies resulted in a pooled estimate mean prevalence of HTN among tribal population to be 11.43% (95% confidence interval: 6.72%-17.21%).

Conclusion

The role of epidemiological transition needs to be read in the context of social anthropology to identify factors preventing HTN among high altitude tribes.

Metabolic Risk Factors and Left Ventricular Diastolic Function in Middle-Aged Chinese Living in the Tibetan Plateau

Background

Data regarding the metabolic risk factors clustering on the risk of left ventricular diastolic dysfunction (LVDD) are lacking among people living at high altitude and under hypoxic conditions. In this study, we explored the association between metabolic risk factor clustering and LVDD among the Tibetan population of China.

Methods and Results

We conducted a cross‐sectional survey in a representative sample of 1963 Tibetans in 2014 to 2016. Grading LVDD was based on recommendations for the evaluation of LV diastolic function by echocardiography (2009). The prevalence of LVDD among 1963 participants (mean age: 51.51 years, 41.11% male) was 34.39%. Odds ratios (95% CI) of LVDD for the 1, 2, and 3 to 5 risk factors clustering were 1.45 (0.96–2.17), 2.68 (1.8–3.98), and 2.9 (1.9–4.43), respectively (P for trend <0.001). The association between metabolic risk factors clustering and LVDD was much more pronounced in the middle‐aged group than in the elderly (P for interaction=0.0170). High altitude was one of the major independent risk factors for LVDD; however, habitation altitude had no significant effect on the association between metabolic risk factors and LVDD (P for interaction=0.1022). The multivariable dominance analysis indicated that abdominal obesity, hypertension, and elevated blood glucose were the significant contributors to LVDD.

Conclusions

There was a significant positive association between the metabolic risk factor clustering number and LVDD among a population living at high altitude, especially in middle‐aged adults. However, habitation altitude itself has no significant effect on the association between metabolic risk factors and LVDD.

The U-shaped association of altitudes with prevalence of hypertension among residents in Tibet, China

We aimed to evaluate the association of altitudes with the prevalence of hypertension among residents aged 15 years and above in Tibet, China. Data for 11,407 Tibetan residents from the National Health Services Survey in 2013 were analyzed. Association between altitudes and prevalence of physician-diagnosed hypertension was assessed by two logistic regression models as follows: (i) a base model adjusted for age and gender, and (ii) a full model additionally adjusted for body mass index, education, marital status, area of residence, distance to the nearest medical institute, smoking, drinking, and exercise. Nonlinear relationship between altitudes and prevalence of hypertension was explored by restricted cubic spline analyses. Sensitivity analyses were conducted by restricting to residents of rural and/or nomadic areas. The prevalence of hypertension was estimated to be 37.6%. We found a U-shaped association between altitudes and prevalence of physician-diagnosed hypertension with a turning point at around 3800 m (12,467 ft). For residents living above 3800 m, a 1000 m increase in altitudes was associated with 2.05 (95% confidence interval [CI]: 1.62-2.61) times higher odds of having physician-diagnosed hypertension, after adjusting for age and gender. When further controlling for all covariates, the odds ratio (OR) dropped to 1.87 (95% CI: 1.46-2.41). For residents living below 3800 m, a 1000 m increase was associated with 0.29 (95% CI: 0.19-0.44) times less likelihood of having physician-diagnosed hypertension in the full model. Sensitivity analyses among residents in rural and/or nomadic areas showed similar associations. To conclude, altitudes were in a U-shaped association with prevalence of hypertension.

Metabolic syndrome and its relation to dietary patterns among a selected urbanised and semi-urbanised Tibetan population in transition from nomadic to settled living environment

OBJECTIVE

To explore the scope of metabolic syndrome (MetS) and its relationship to the major dietary patterns among an urbanised and semi-urbanised Tibetan population in transition from nomadic to settled settings.

DESIGN

Cross-sectional.

SETTING

Community-based.

PARTICIPANTS

Urbanised and semi-urbanised Tibetan adults (n 920, aged 18-90 years), who have moved from nomadic to settled living environments, answered questionnaires on food consumption frequency and lifestyle characteristics through structured face-to-face interviews and completed anthropometric measurement and metabolic biomarker tests.

RESULTS

MetS prevalence was 30·1 % in males and 32·1 % in females. Low HDL-cholesterol and central obesity were the leading metabolic abnormalities (86·3 and 55·8 %, respectively). Three major dietary patterns - urban, western and pastoral - were identified. Beef/mutton was an important food group for all three identified dietary patterns. In addition, the urban dietary pattern was characterised by frequent consumption of vegetables, tubers/roots and refined carbohydrates; the western pattern was characterised by sweetened drinks, snacks and desserts; and the pastoral pattern featured tsamba (roasted Tibetan barley), Tibetan cheese, butter tea/milk tea and whole-fat dairy foods. Individuals in the highest quintile of urban dietary pattern scores were found to be at a higher risk of developing MetS (OR 2·43, 95 % CI 1·41, 4·18) and central obesity (OR 1·91, 95 % CI 1·16, 3·14) after controlling for potential confounders.

CONCLUSIONS

MetS was common among urbanised and semi-urbanised Tibetan adult population in transition. The urban dietary pattern, in particular, was a risk factor for MetS. To prevent MetS, nutrition interventions need to be tailored to address the variety of local diet patterns to promote healthy eating.

Metabolic syndrome in native populations living at high altitude: a cross-sectional survey in Derong, China

OBJECTIVE

The metabolic syndrome is a major risk factor for cardiovascular disease. Little information exists on the prevalence of the metabolic syndrome at high-altitude areas in China. We aimed to estimate the prevalence of metabolic syndrome and its individual components at high altitude.

METHODS

A cross-sectional survey of 5053 adults living in Derong from elevation of 2060 to 3820 m was carried out in 2013. Metabolic syndrome was defined according to the Chinese Diabetes Society criteria.

RESULTS

The overall prevalence of metabolic syndrome was 3.6% (5.9% in men and 1.8% in women) in Derong, China. Obesity and hypertension were more prevalent among adults than dyslipidaemia and hyperglycaemia at high altitude. The prevalence of metabolic syndrome was higher in township than countryside residents (6.6%, 11.9% in men and 1.5% in women vs 3.0%, 4.6% in men and 1.8% in women). Men with age 30-59 years old had a much higher prevalence of metabolic syndrome than women. Men, township, middle and old age residents had a higher risk of metabolic syndrome. The risk of obesity and dyslipidaemia decreased and the risk of hypertension increased in very high altitude (≥3000 m) residents.

CONCLUSION

In Derong, despite the relatively low prevalence of metabolic syndrome, hypertension and obesity are more prevalent in adult residents. And metabolic syndrome is more concentrated in township and male residents. These people also have a higher risk of metabolic syndrome. Therefore, it is necessary to develop a national strategy for the prevention and treatment of metabolic syndrome for high-risk population at high altitude in China.

The prevalence of hyperuricemia and its correlates in Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China

Background

Hyperuricemia is a common and serious public health problem. There has been no broad epidemiological survey of hyperuricemia in China, especially in Tibetan area. This study was therefore investigated the prevalence of hyperuricemia and its correlated factors among people aged 18–85 years in Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China.

Methods

We carried out a cross-sectional study among 3093 participants in Ganzi Tibetan Autonomous Prefecture using questionnaires in face-to-face interviews, anthropometric measurements and biochemical tests. We included 1416 subjects with complete data including serum uric acid and medical history to analyze the prevalence of hyperuricemia and correlated factors. Hyperuricemia was defined as a fasting serum uric acid level higher than 420 μmol/L in men and 360 μmol/L in women.

Results

The overall crude prevalence of hyperuricemia was 37.2%, and was greater in men than women (41% vs 34.4%, P = 0.011). The age-adjusted prevalence was 33.0%. Characteristics linked to hyperuricemia were farmers-herdsmen (OR: 1.749, 95% CI: 1.022–2.992), low to moderate education level (low OR:1.57, 95% CI: 1.102–2.237; moderate OR: 1.86, 95% CI: 1.167–2.963), current drinking (OR: 1.795, 95% CI: 1.193–2.702), hypertension (OR: 1.48, 95% CI: 1.091–2.006), higher body mass index (1 unit increase) (OR: 1.116, 95% CI: 1.077–1.156) and higher serum creatinine (1 unit increase) (OR: 1.046, 95% CI: 1.034–1.059). Serum uric acid was positively related to triglycerides and total cholesterol and negatively related to high density lipoprotein cholesterol in all subjects. Hyperuricemia was a risk factor for high triglyceride ((OR: 2.13, 95% CI: 1.156–3.9266) and high total cholesterol (OR: 2.313, 95% CI: 1.364–3.923) in men and for high low-density lipoprotein cholesterol (OR: 2.696, 95% CI: 1.386–5.245) in women.

Conclusion

There is a high prevalence of hyperuricemia in Ganzi Tibetan Autonomous Prefecture. The government needs to prevent and manage hyperuricemia in this area.

Discordance of metabolic syndrome and abdominal obesity prevalence according to different criteria in Andean highlanders: A community-based study

AIMS

There is no consensus as to which Metabolic Syndrome (MetS) definition to use for South-American populations. The aim of this study is to compare the prevalence of MetS and abdominal obesity using different criteria in Andean adults aged 40 and older living permanently at high altitude.

METHODS

We conducted a cross-sectional study in Chivay (Andean highlands). 237 participants were included. Anthropometric measurements, glucose and lipid assessments were done in all subjects. Adult Treatment Panel III (ATPIII) and International Diabetes Federation (IDF) criteria for MetS were used. Abdominal obesity prevalence was determined using the American Diabetes Association (ADA), IDF, and PREVENCION Study criteria. Cohen's Kappa coefficient (κ) was analyzed to assess agreement level between different criteria. Multiple regression analyses were performed to find predictors for waist circumference.

RESULTS

MetS was identified in 28.7% (95%CI=23.8-33.5) using ATPIII criteria, and 37.9% (95%CI=32.7-43.0) using IDF criteria, with higher prevalence in women. The κ statistics for agreement between both criteria was 0.775 (95%CI=0.690-0.859). Abdominal obesity prevalence according to ADA, IDF, and PREVENCION criteria was 35.9% (95%CI=29.7-42.0), 75.9% (95%CI=70.5-81.4), and 42.6% (95%CI=36.3-49.0), respectively. Agreement between ADA and PREVENCION criteria was highest (κ=0.859, 95%CI=0.792-0.925). The strongest predictors for higher waist circumference values were triglycerides and BMI in women, and systolic blood pressure, triglycerides, fasting plasma glucose, and HDL-cholesterol in men.

CONCLUSIONS

MetS according to ATP III and IDF criteria was highly prevalent. IDF criteria identified a larger number of subjects with MetS. Different abdominal obesity criteria tended to show variation when applied to our sample population.

Lipid Profiles, Glycated Hemoglobin, and Diabetes in People Living at High Altitude in Nepal

This study aimed to describe lipid profiles and the distribution of glycated hemoglobin (HbA1c) in a sample of a high altitude population of Nepal and to explore associations between these metabolic risk variables and altitude. A cross-sectional survey of cardiovascular disease and associated risk factors was conducted among 521 people living at four different altitude levels, all above 2800 m, in the Mustang and Humla districts of Nepal. Urban participants (residents at 2800 m and 3620 m) had higher total cholesterol (TC) and triglyceride (TG) than rural participants. A high ratio of TC to high-density lipoprotein-cholesterol (HDL) (TC/HDL ≥ 5.0) was found in 23.7% (95% CI 19.6, 28.2) and high TG (≥1.7 mmol/L) in 43.3% (95% CI 38.4, 48.3) of participants overall. Mean HbA1c levels were similar at all altitude levels although urban participants had a higher prevalence of diabetes. Overall, 6.9% (95% CI 4.7, 9.8) of participants had diabetes or were on hypoglycaemic treatment. There was no clear association between lipid profiles or HbA1c and altitude in a multivariate analysis adjusted for possible confounding variables. Residential settings and associated lifestyle practices are more strongly associated with lipid profiles and HbA1c than altitude amongst high altitude residents in Nepal.

The prevalence of obesity and metabolic syndrome in Tibetan immigrants living in high altitude areas in Ladakh, India

OBJECTIVE

To examine the prevalence of obesity and related cardiovascular disease risk factors among Tibetan immigrants living in high altitude areas.

RESEARCH METHODS & PROCEDURES

A total of 149 Tibetan immigrants aged 20 years and over were recruited in 2016 in Ladakh, India. Anthropometric indices and biochemical factors were measured. Using the provided Asia-Pacific criteria from the World Health Organization, overweight and obese status were determined. Metabolic syndrome (MetS) was defined according to the American Heart Association.

RESULTS

In general, men were older, taller, and had a greater amount of fasting glucose, and uric acid when compared to women. The prevalence of overweight, general obesity, and central obesity was 23.4, 42.6, and 42.6% in men and 7.8, 64.7, and 69.6% in women, respectively. The prevalence of MetS was 10.6% in men and 33.3% in women, respectively. In older subjects, the prevalence of obesity and MetS was found to be greater. In both genders, the prevalence of hypertension, central obesity, and MetS was significantly different among these body mass index (BMI) groups. Compared to the non-central obesity group, the central obesity group has higher weight, BMI, body fat, hip circumference, systolic and diastolic BP, and prevalence of hypertension. No relationship was found between the prevalence of diabetes and fasting glucose and BMI groups or central obesity groups in both genders.

CONCLUSIONS

Among this group of Tibetan immigrants living in high altitude areas, women have a higher prevalence of obesity and MetS than men. No relationship was found between diabetes and obesity.

Diabetes in Immigrant Tibetan Muslims in Kashmir, North India

Tibetan Muslims have migrated from Lhasa (3000 m altitude) to Srinagar, India (altitude 1500 m) about 55 years back. We set out to study the prevalence of diabetes and prediabetes among this immigrant population. All consenting adults aged ≥18 years were questioned about a previous history of diabetes or any other medical history. Anthropometric data were recorded. Fasting blood glucose was measured in duplicate by Accu-check glucometer and HbA1C levels were measured. Of the 281 participants, 26 (9.25%) had diabetes whereas 46 (16.4%) had pre-diabetes; 24 reporting doctor-diagnosed diabetes. Participants with diabetes/pre-diabetes were more likely to be obese, smokers and hypertensive. Multiple logistic regression analysis revealed age to be significantly associated with a higher prevalence of diabetes. One in four adults ≥18 years among Tibetan Muslims have diabetes or prediabetes. Migration to lower altitude could have contributed to this high prevalence.

Increased Cardiometabolic Risk and Worsening Hypoxemia at High Altitude

Miele, Catherine H., Alan R. Schwartz, Robert H. Gilman, Luu Pham, Robert A. Wise, Victor G. Davila-Roman, Jonathan C. Jun, Vsevolod Y. Polotsky, J. Jaime Miranda, Fabiola Leon-Velarde, and William Checkley. Increased cardiometabolic risk and worsening hypoxemia at high altitude. High Alt Med Biol. 17:93-100, 2016.-Metabolic syndrome, insulin resistance, diabetes, and dyslipidemia are associated with an increased risk of cardiovascular disease. While excessive erythrocytosis is associated with cardiovascular complications, it is unclear how worsening hypoxemia of any degree affects cardiometabolic risk factors in high-altitude populations. We studied the relationship between daytime resting oxyhemoglobin saturation and cardiometabolic risk factors in adult participants living in Puno, Peru (3825 m above sea level). We used multivariable logistic regression models to study the relationship between having a lower oxyhemoglobin saturation and markers of cardiometabolic risk. Nine hundred and fifty-four participants (mean age 55 years, 52% male) had information available on pulse oximetry and markers of cardiometabolic risk. Average oxyhemoglobin saturation was 90% (interquartile range 88%-92%) and 43 (4.5%) had excessive erythrocytosis. Older age, decreased height-adjusted lung function, and higher body mass index (BMI) were associated with having an oxyhemoglobin saturation ≤85%. When adjusting for age, sex, socioeconomic status, having excessive erythrocytosis, and site, we found that each 5% decrease in oxyhemoglobin saturation was associated with a higher adjusted odds of metabolic syndrome (OR = 1.35, 95% CI: 1.07-1.72, p < 0.04), insulin resistance as defined by homeostasis model assessment-insulin resistance (HOMA-IR) >2 mass units (OR = 1.29, 95% CI: 1.00-1.67, p < 0.05), hemoglobin A1c ≥6.5% (OR = 1.66, 95% CI: 1.09-2.51, p < 0.04), and high sensitivity C-reactive protein (hs-CRP) ≥3 mg/L (OR = 1.46, 95% CI: 1.09-1.96, p < 0.01). In high-altitude populations in Puno, Peru, a higher BMI and lower pulmonary function were associated with lower resting daytime oxyhemoglobin saturation. Lower resting oxyhemoglobin saturation, in turn, was associated with higher odds of having multiple unfavorable cardiometabolic factors. Worsening hypoxia of any degree in high-altitude dwellers may be an independent risk factor for cardiovascular disease.

Glucose intolerance associated with hypoxia in people living at high altitudes in the Tibetan highland

OBJECTIVES

To clarify the association between glucose intolerance and high altitudes (2900-4800 m) in a hypoxic environment in Tibetan highlanders and to verify the hypothesis that high altitude dwelling increases vulnerability to diabetes mellitus (DM) accelerated by lifestyle change or ageing.

DESIGN

Cross-sectional epidemiological study on Tibetan highlanders.

PARTICIPANTS

We enrolled 1258 participants aged 40-87 years. The rural population comprised farmers in Domkhar (altitude 2900-3800 m) and nomads in Haiyan (3000-3100 m), Ryuho (4400 m) and Changthang (4300-4800 m). Urban area participants were from Leh (3300 m) and Jiegu (3700 m).

MAIN OUTCOME MEASURE

Participants were classified into six glucose tolerance-based groups: DM, intermediate hyperglycaemia (IHG), normoglycaemia (NG), fasting DM, fasting IHG and fasting NG. Prevalence of glucose intolerance was compared in farmers, nomads and urban dwellers. Effects of dwelling at high altitude or hypoxia on glucose intolerance were analysed with the confounding factors of age, sex, obesity, lipids, haemoglobin, hypertension and lifestyle, using multiple logistic regression.

RESULTS

The prevalence of DM (fasting DM)/IHG (fasting IHG) was 8.9% (6.5%)/25.1% (12.7%), respectively, in all participants. This prevalence was higher in urban dwellers (9.5% (7.1%)/28.5% (11.7%)) and in farmers (8.5% (6.1%)/28.5% (18.3%)) compared with nomads (8.2% (5.7%)/15.7% (9.7%)) (p=0.0140/0.0001). Dwelling at high altitude was significantly associated with fasting IHG+fasting DM/fasting DM (ORs for >4500 and 3500-4499 m were 3.59/4.36 and 2.07/1.76 vs <3500 m, respectively). After adjusting for lifestyle change, hypoxaemia and polycythaemia were closely associated with glucose intolerance.

CONCLUSIONS

Socioeconomic factors, hypoxaemia and the effects of altitudes >3500 m play a major role in the high prevalence of glucose intolerance in highlanders. Tibetan highlanders may be vulnerable to glucose intolerance, with polycythaemia as a sign of poor hypoxic adaptation, accelerated by lifestyle change and ageing.

Prevalence and Clustering of Cardiovascular Disease Risk Factors among Tibetan Adults in China: A Population-Based Study

Objectives

The prevalence of cardiovascular disease risk factors has increased worldwide. However, the prevalence and clustering of cardiovascular disease risk factors among Tibetans is currently unknown. We aimed to explore the prevalence and clustering of cardiovascular disease risk factors among Tibetan adults in China.

Methods

In 2011, 1659 Tibetan adults (aged ≥18 years) from Changdu, China were recruited to this cross-section study. The questionnaire, physical examinations and laboratory testing were completed and the prevalence of cardiovascular disease risk factors, including hypertension, diabetes, overweight/obesity, dyslipidemia, and current smoking, were counted. The association between the clustering of cardiovascular disease risk factors and demographic characteristics, and geographic altitude were assessed.

Results

The age-standardized prevalence of hypertension, diabetes, overweight or obesity, dyslipidemia, and current smoking were 62.4%, 6.4%, 34.3%, 42.7%, and 6.1%, respectively, and these risk factors were associated with age, gender, education level, yearly family income, altitude, occupation, and butter tea consumption (P < 0.05). Overall, the age-adjusted prevalence of clustering of ≥1, ≥2, and ≥3 cardiovascular disease risk factors were 79.4%, 47.1%, and 20.9%, respectively. There appeared higher clustering of ≥2 and ≥3 cardiovascular disease risk factors among Tibetans with higher education level and family income yearly, and those living at an altitude < 3500 m and in a township.

Conclusions

The prevalence of cardiovascular disease risk factors, especially hypertension, was high in Tibetans. Moreover, there was an increased clustering of cardiovascular disease risk factors among those with higher socioeconomic status, lamas and those living at an altitude < 3500 m. These findings suggest that without the immediate implementation of an efficient policy to control these risk factors, cardiovascular disease will eventually become a major disease burden among Tibetans.

Relationship between altitude and the prevalence of hypertension in Tibet: a systematic review

Introduction

Hypertension is a leading cause of cardiovascular disease, which is the cause of one-third of global deaths and is a primary and rising contributor to the global disease burden. The objective of this systematic review was to determine the prevalence and awareness of hypertension among the inhabitants of Tibet and its association with altitude, using the data from published observational studies.

Methods

We conducted electronic searches in Medline, Embase, ISI Web of Science and Global Health. No gender or language restrictions were imposed. We assessed the methodological characteristics of included studies using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria. Two reviewers independently determined the eligibility of studies, assessed the methodology of included studies and extracted the data. We used meta-regression to estimate the degree of change in hypertension prevalence with increasing altitude.

Results

We identified 22 eligible articles of which eight cross-sectional studies with a total of 16 913 participants were included. The prevalence of hypertension ranged between 23% and 56%. A scatter plot of altitude against overall prevalence revealed a statistically significant correlation (r=0.68; p=0.04). Meta-regression analysis revealed a 2% increase in the prevalence of hypertension with every 100 m increase in altitude (p=0.06). The locations and socioeconomic status of subjects affected the awareness and subsequent treatment and control of hypertension.

Conclusions

The results from cross-sectional studies suggest that there is a significant correlation between altitude and the prevalence of hypertension among inhabitants of Tibet. The socioeconomic status of the inhabitants can influence awareness and management of hypertension. Very little research into hypertension has been conducted in other prefectures of Tibet where the altitude is much higher. Further research examining the impact of altitude on blood pressure is warranted.

Prevalence of hypertension at high altitude: cross-sectional survey in Ladakh, Northern India 2007-2011

OBJECTIVE

Prevalence of hypertension was examined in a widely dispersed (45 110 km(2)) representative group of Ladakhi in Northern India. The influence of hypoxic environment of wide-ranged altitude (2600-4900 m) and lifestyle change on hypertension was studied.

METHODS

2800 participants (age 20-94 years) were enrolled. Systolic blood pressure ≥140 mm Hg and/or diastolic blood pressure of ≥90 mm Hg and/or taking current anti-hypertensive medicine was defined as hypertension. Height and weight for body mass index and SpO₂ were examined. The rural population comprised six subdivisions with a distinct altitude, dietary and occupational pattern. Participants in the urban area of Leh consist of two groups, that is, migrants settled in Leh from the Changthang nomadic area, and dwellers born in Leh. The prevalence of hypertension in the two groups was compared with that in the farmers and nomads in rural areas. The effects of ageing, hypoxia, dwelling at high altitude, obesity, modernised occupation, dwelling in an urban area, and rural-to-urban migration to hypertension were analysed by multiple logistic regression.

RESULTS

The prevalence of hypertension was 37.0% in all participants and highest in migrants settled in Leh (48.3%), followed by dwellers born in Leh town (41.1%) compared with those in rural areas (33.5). The prevalence of hypertension in nomads (all: 27.7%, Tibetan/Ladakhi: 19.7/31.9%)) living at higher altitude (4000-4900 m) was relatively low. The associated factors with hypertension were ageing, overweight, dwelling at higher altitude, engagement in modernised sedentary occupations, dwelling in urban areas, and rural-to-urban migration. The effects of lifestyle change and dwelling at high altitude were independently associated with hypertension by multivariate analysis adjusted with confounding factors.

CONCLUSIONS

Socioeconomic and cultural factors play a big role with the effect of high altitude itself on high prevalence of hypertension in highlanders in Ladakh.

Plasma and liver lipid profiles in rats exposed to chronic hypobaric hypoxia: changes in metabolic pathways

Lipid metabolism under chronic hypoxia (CH) has not received equal attention as intermittent hypoxia (IH). To determine the CH-induced changes in plasma and liver, as well as the mRNA and protein expression of two key enzymes in the triglyceride and cholesterol biosynthesis pathways, SREBP-1 (HMG-CoA reductase) and SREBP-2 (SCD-1), we exposed adult male Wistar rats to CH (4600 m; n=15) for 30 days compared to normoxic rats (n=15). The CH rats exhibited weight loss (p<0.001), higher hematocrit (%), and higher hemoglobin (g/dL) (p<0.01). In the plasma of CH rats, total cholesterol and LDL-cholesterol increased at day 15. VLDL-cholesterol and triglycerides (p<0.01) greatly increased (35%), while HDL-cholesterol decreased (p<0.01). Triglycerides and VLDL-cholesterol remained elevated by 28% at day 30 (p<0.01). Hepatic triglycerides increased two-fold, while total cholesterol increased by 51% (p<0.001; p<0.05). Upregulation of SCD-1 mRNA and protein was observed in the CH rats (p<0.01); however, no differences were observed in HMG-CoA reductase mRNA or protein expression in both groups. In conclusion, CH, like IH, alters lipid profiles by increasing triglycerides in the plasma and liver and upregulating triglyceride biosynthesis without affecting the cholesterol biosynthetic pathway. Additional involved mechanisms require further study because of the importance of lipids in cardiovascular risk.

Chronic intermittent high altitude exposure, occupation, and body mass index in workers of mining industry

The obesity and overweight rates in population exposed to chronic intermittent exposure to high altitudes are not well studied. The aim of the retrospective study was to evaluate whether there are differences in body mass index in different occupation groups working in intermittent shifts at mining industry at high altitude: 3800-4500 meters above sea level. Our study demonstrated that obesity and overweight are common in workers of high altitude mining industry exposed to chronic intermittent hypoxia. The obesity rate was lowest among miners as compared to blue- and white-collar employees (9.5% vs. 15.6% and 14.7%, p=0.013). Obesity and overweight were associated with older age, higher rates of increased blood pressure (8.79% and 5.72% vs. 1.92%), cholesterol (45.8% and 45.6% vs. 32.8%) and glucose (4.3% and 1.26% vs. 0.57%) levels as compared to normal body mass index category (p<0.0001 for all). There were differences in patterns of cholesterol and glucose levels in men and women employees according to occupation type. In conclusion, obesity and overweight rates are prevalent and associated with increase in blood pressure, cholesterol, and glucose levels in workers of mining industry exposed to intermittent high-altitude hypoxia. Therefore, assessment and monitoring of body mass index seems to be essential in those who live and work at high altitudes to supply the correct nutrition, modify risk factors, and prevent related disorders.

Chemical composition and antioxidant capacities of phytococktail extracts from trans-Himalayan cold desert

BACKGROUND

Himalayan plants are widely used in traditional system of medicine both as prophylactics and therapeutics for high altitude maladies. Our aim was to evaluate the antioxidant capacities and bioactive compounds of methanol and n-hexane extracts of the phytococktail comprising of sea buckthorn (Hippophae rhamnoides), apricot (Prunus armeniaca) and roseroot (Rhodiola imbricata) from trans-Himalaya.

METHODS

The 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and nitric oxide (NO) radical scavenging capacities and lipid peroxidation inhibition (LPI) property of the extracts were determined. Total antioxidant power was determined by ferric reducing/antioxidant power (FRAP) assay. Total polyphenol, flavonoid, flavonol, proanthocyanidin and carotenoid were also estimated for both extracts. We have identified and quantified the phyto-chemotypes present in the methanol and n-hexane extracts by hyphenated gas chromatography/mass spectrometry (GC/MS) technique.

RESULTS

Antioxidant capacity assays using DPPH, ABTS, NO, LPI and FRAP exhibited analogous results where the phytococktail showed high antioxidant action. The phytococktail was also found to possess high quantity of total polyphenol, flavonoid, flavonol and carotenoid. A significant and linear correlation was found between the antioxidant capacities and bioactive principles. A total of 32 phyto-chemotypes were identified from these extracts by GC/MS chemometric fingerprinting. Major phyto-chemotypes identified by GC/MS were glycosides, phenylpropanoids and derivatives, terpenoids, alkaloids, phytosterols, fatty acids and esters, alkaloids and derivatives, organic acid esters and aromatic ethers with positive biological and pharmacological actions.

CONCLUSION

The phytococktail extracts were found to contain considerable amount of diverse bioactive compounds with high antioxidant capacities. The presence of hydrophilic and lipophilic antioxidants in the phytococktail could have contributed to the higher antioxidant values. Hence, the phytococktail could be used as natural source of antioxidants to ameliorate disorders associated with oxidative stress.