Asvini K Subasinghe

Do the socioeconomic and hypertension gradients in rural populations of low- and middle-income countries differ by geographical region? A systematic review and meta-analysis

BACKGROUND Of the 1 billion people with hypertension globally, two-thirds reside in low- and middle-income countries (LMICs). The risk of hypertension in LMICs is thought to be positively associated with socioeconomic status (SES). However, recent studies have provided data inconsistent with this concept. Thus, we assessed the association between SES and hypertension in rural populations of LMICs. Further, we explored whether this association differs according to geographical region. METHODS Through a search of databases we identified population-based studies that presented risk estimates for the association between SES, or any of its proxies, and hypertension. Meta-analyses were conducted using a random effects model. RESULTS Overall, no association was detected between educational status and hypertension, whereas a positive association was observed with income. Interestingly, educational status was inversely associated with hypertension in East Asia {effect size [ES] 0.82 [95% confidence interval (CI) 0.78, 0.87]} but positively associated in South Asia [ES 1.28 (95% CI 1.14, 1.43)]. Higher income, household assets or social class were positively associated with hypertension in South Asia whereas no association was detected in East Asia and Africa. Compared with other occupations, farmers or manual labourers were associated with a lower risk for hypertension. Further, in regions such as Latin America, few studies were identified that fulfilled our inclusion criteria. CONCLUSIONS We provide evidence that the association between hypertension and SES in rural populations of LMICs in Asia varies according to geographical region. This has important implications for targeting intervention strategies aimed at high-risk populations in different geographical regions.

Association between farming and chronic energy deficiency in rural South India.

Objective To examine factors associated with chronic energy deficiency (CED) and anaemia in disadvantaged Indian adults who are mostly involved in subsistence farming. Design A cross-sectional study in which we collected information on socio-demographic factors, physical activity, anthropometry, blood haemoglobin concentration, and daily household food intake. These data were used to calculate body mass index (BMI), basal metabolic rate (BMR), daily energy expenditure, and energy and nutrient intake. Multivariable backward stepwise logistic regression was used to assess socioeconomic and lifestyle factors associated with CED (defined as BMI<18 kg/m2) and anaemia. Setting The study was conducted in 12 villages, in the Rishi Valley, Andhra Pradesh, India. Subjects Individuals aged 18 years and above, residing in the 12 villages, were eligible to participate. Results Data were available for 1178 individuals (45% male, median age 36 years (inter quartile range (IQR 27–50)). The prevalence of CED (38%) and anaemia (25%) was high. Farming was associated with CED in women (2.20, 95% CI: 1.39–3.49) and men (1.71, 95% CI: (1.06–2.74). Low income was also significantly associated with CED, while not completing high school was positively associated with anaemia. Median iron intake was high: 35.7 mg/day (IQR 26–46) in women and 43.4 mg/day (IQR 34–55) in men. Conclusions Farming is an important risk factor associated with CED in this rural Indian population and low dietary iron is not the main cause of anaemia. Better farming practice may help to reduce CED in this population.

Association between salt and hypertension in rural and urban populations of low to middle income countries: a systematic review and meta-analysis of population based studies.

BACKGROUND AND OBJECTIVES The prevalence of hypertension, the greatest contributor to mortality globally, is increasing in low-and-middle income countries (LMICs). In urban regions of LMICs, excessive salt intake is associated with increased risk of hypertension. We aimed to determine whether this is the case in rural regions as well. METHODS AND STUDY DESIGN We performed a meta-analysis of studies in rural and urban areas of LMICs in which the association of salt and hypertension were assessed using multivariable models. RESULTS We identified 18 studies with a total of 134,916 participants. The prevalence of high salt intake ranged from 21.3% to 89.5% in rural and urban populations. When salt was analysed as a continuous variable, a greater impact of salt on hypertension was found in urban (n=4) (pooled effect size (ES) 1.42, 95% CI 1.19, 1.69) than in rural populations (n=4) (pooled ES 1.07, 95% CI 1.04, 1.10, p for difference <0.001). In studies where salt was analysed continuously, a greater impact of salt on hypertension was observed in lean rural populations (BMI <23 kg/m2) than in non-lean rural populations (BMI >=23 kg/m2, p for difference <0.001). CONCLUSIONS The prevalence of high salt intake is similar in rural and urban regions. Excessive salt intake has a greater impact on the prevalence of hypertension in urban than rural regions. BMI appears to modify the relationship between salt and hypertension in rural populations.

Rejoinder: Socioeconomic gradients and hypertension in low- and middle-income countries: a straw man and no solutions

Rejoinder: Socioeconomic gradients and hypertension in lowand middle-income countries: a straw man and no solutions From Doreen Busingye,* Roger G Evans, Simin Arabshahi, Asvini K Subasinghe, Michaela A Riddell and Amanda G Thrift Department of Medicine, School of Clinical Sciences, and Department of Physiology, Monash University, Melbourne, VIC, Australia and Stroke Division, Florey Neuroscience Institutes, Heidelberg, VIC, Australia

PS 06-06 ASSOCIATION BETWEEN INFLAMMATION AND HYPERTENSION IN A RURAL, DISADVANTAGED INDIAN POPULATION IS DIFFERENT FOR MEN AND WOMEN

Objective: There is some evidence that low grade inflammation is associated with an increased risk of hypertension, but whether this is the case in disadvantaged populations in India has not been established. We aimed to assess the risk of hypertension associated with high sensitivity C-reactive protein (CRP), a marker of inflammation, in a rural population of Indians living in poverty. Design and Method: In a case-control study in 58 villages in southwestern Andhra Pradesh, we age- and sex-matched 300 cases with hypertension to 300 controls without hypertension. Blood pressure (BP) was measured according to a strict protocol. CRP (Immulite 2000xpi) was categorized into three groups: < 1 mg/L (reference category), 1 to <3 mg/L, and ≥ 3 mg/L. Conditional logistic regression was used to determine associations between CRP and hypertension (BP ≥ 140/90 mmHg), adjusted for income, smoking, central obesity, and residual effects of age. Results: In this population, 34% of participants had CRP levels below 1 mg/L and 31% ≥ 3 mg/L. We were unable to detect an association between hypertension and CRP levels of 1 to < 3 mg/L (Odds Ratio (OR) 1.29, 95% Confidence Interval (95%CI) 0.83 to 2.00) or CRP ≥ 3 mg/L (OR 1.33, 95%CI 0.84 to 2.10). When investigating these associations by sex, there was an association between CRP and hypertension in men (levels of 1 to < 3 mg/L [OR 1.80, 95%CI 1.00 to 3.24] and ≥ 3 mg/L [OR 1.99, 95%CI 1.04 to 3.82]). No similar association was found in women (levels of 1 to < 3 mg/L [OR 0.79, 95%CI 0.39 to 1.60] and ≥ 3 mg/L [OR 0.80, 95%CI 0.41 to 1.56]). Conclusions: We provide evidence of a cross-sectional association between CRP and hypertension in men, but not in women, in this rural disadvantaged population. CRP could add to the prediction of future CVD in rural communities, particularly in men, but this requires further testing.

MPS 08-06 Socio-economic position and diet play important roles in the development of hypertension in a setting of disadvantage

Objective: Poor diet quality and low socio-economic position (SEP) have been associated with hypertension in high income and urban populations. However, limited evidence exists for the relationship between diet, SEP and blood pressure in disadvantaged rural populations. We aimed to assess the impact of SEP and diet on hypertension in a disadvantaged rural South Indian population. Design and Method: In a case-control study of hypertension, conducted in 58 villages in rural Andhra Pradesh, 300 cases were matched 1:1 by age and sex. Blood pressure and anthropometry were measured using a strict protocol. Sodium and potassium were measured from 24-hour urine samples. Participants were interviewed to obtain socio-demographic, lifestyle and dietary information. Conditional logistic regression was used to determine factors associated with hypertension (blood pressure ≥ 140/90 mmHg). Results: The median age was 60 years (interquartile range 20); 56% were men. Median salt intake did not differ significantly between cases and controls (7.2 vs. 7.3 grams/day, P = 0.9). The median sodium-to-potassium ratio was greater in cases than controls (8.4 vs. 8.1, P = 0.007). In multivariable analyses, high SEP (odds ratio (OR) 3.2, 95% confidence interval (CI) 1.4–7.7, P = 0.008) and physical inactivity (OR 3.0, 95% CI 2.0 − 4.6 P < 0.001) were associated with a greater odds of hypertension. Polygamy (OR 2.9, 95% CI 1.2–7.2, P = 0.02) and consuming alcohol (OR 2.1, 95% CI 1.2–3.8, P = 0.008) were associated with a greater odds of hypertension in men, whereas obesity (OR 2.6, P = 0.05) was associated with hypertension in women. Conclusions: The main drivers of hypertension in this population are poor diet, SEP and lifestyle factors such as physical inactivity and consuming alcohol. Therefore strategies to improve diet quality and lifestyle behaviors may help reduce the burden of hypertension in this disadvantaged Indian population.

PS 06-09 SEX DIFFERENCES IN THE ASSOCIATION BETWEEN ADIPOSITY AND HYPERTENSION IN A DISADVANTAGED RURAL INDIAN POPULATION

Objective: Obesity is associated with hypertension in high income countries, but less is known about this association in rural regions of low- to middle-income countries. We aimed to assess the risk of hypertension associated with obesity in a disadvantaged region of rural South India. Design and Method: We undertook a case-control study in 58 villages in southwestern Andhra Pradesh. Three hundred cases with hypertension were age- and sex-matched to 300 controls without hypertension. Blood pressure (BP), waist circumference, waist-hip ratio (WHR), and body mass index (BMI) were measured according to strict protocols. Percent body fat was estimated using skinfold thickness measured at the biceps, triceps, subscapular and supra-iliac regions. Conditional logistic regression was used to determine associations between each measurement of body fat and hypertension (BP ≥ 140/90 mmHg), adjusted for age and disadvantage. Linear regression was used to determine the relationship between continuous measurements of adiposity and systolic and diastolic BP. Results: Overall, mean BMI was 20.5 kg/m2, 29% of people were underweight, 9% were overweight and 14% were obese. Hypertension was positively associated with obesity, as defined by a BMI ≥ 23 kg/m2 (Odds Ratio (OR) 1.8, 95% Confidence Interval (CI) 1.1–3.0), waist circumference (OR 2.2, 95% CI 1.3–3.8) and WHR (OR 2.1, 95% CI 1.4–3.0), but not percent body fat. WHR was a better predictor of hypertension in women (OR 3.3, 95% CI 1.8–6.0) than men (OR 1.5, 95% CI 0.92–2.4, p for difference 0.04). All measures of adiposity were associated with diastolic BP (p < 0.05), but not systolic BP. Similar patterns were observed in men and women. Conclusions: Our findings confirm that even in this relatively thin rural sample in India, BMI, waist circumference and WHR are strongly associated with hypertension. Central adiposity may play a greater role in the pathogenesis of hypertension in women in these populations. Those with high waist circumference, particularly women, should be screened for hypertension.

Novel dietary intake assessment in populations with poor literacy.

BACKGROUND AND OBJECTIVES Cultural and/or environmental barriers make the assessment of dietary intake in rural populations challenging. We aimed to assess the accuracy of a meal recall questionnaire, adapted for use with impoverished South Indian populations living in rural areas. METHODS AND STUDY DESIGN Dietary data collected by recall versus weighed meals were compared. Data were obtained from 45 adults aged 19-85 years, living in rural Andhra Pradesh, who were recruited by convenience sampling. Weighed meal records (WMRs) were conducted in the household by a researcher aided by a trained field worker. The following day, field workers conducted a recall interview with the same participant. Eight life size photographs of portions of South Indian foods were created to aid each participants recall and a database of nutrients was developed to calculate nutrient intake. Pearson correlations were used to assess the strength of associations between intake of energy and nutrients calculated from meal recalls versus WMRs. Least products regression was conducted to examine fixed and proportional bias. Bland-Altman plots were constructed to measure systematic or differential bias. RESULTS Significant correlations were observed between estimates for energy and nutrients obtained by the two methods (r2=0.19-0.67, p<0.001). No systematic bias was detected by Bland-Altman plots. Recall method underestimated the intake of protein and fat in a manner proportional to the level of intake. CONCLUSIONS Our culturally adapted meal recall questionnaire provides an accurate measure for assessment of the intake of energy, macronutrients and some micronutrients in rural Indian populations.

Authors’ Response to: Data sources for measuring the socioeconomic gradient of hypertension in rural populations of low- and middle-income countries

We thank Dr Raban for her recent correspondence which highlights an important issue in the use of data from health information systems to provide a more inclusive analysis of the association between socioeconomic position (SEP) and hypertension in various regions of lowand middle-income countries. We agree there may be some advantages to using these relatively recent data, and we applaud Dr Raban for re-highlighting the availability of these unpublished data sources. However, as the author acknowledged, some of the surveys are disadvantaged by poor response rates, some are limited to women only and others do not include individuals in older age groups. If severely restricted, this could limit the interpretation of the findings. In our systematic review and meta-analysis, we included data that were representative of the entire population and so included older individuals, who are more likely to have hypertension. Nevertheless, because the Measure Demographic and Health Surveys (DHS) and the Study on Global Ageing and Adult Health (SAGE) data are unit level, this would enable more comprehensive exploration of the association between SEP and hypertension in different settings and groups. In conclusion, as these data grow and more regions are covered, there will be more opportunities to further assess differences in the association between SEP and noncommunicable diseases between and within regions. We encourage the continued promotion of the availability of these data to a wider range of researchers.