Hypertension and Malnutrition as Health Outcomes Related to Ecosystem Services
Human health and well-being is related to the provision of nutrition and food diversity for each socio-ecological system within the study area. Analysis of data from the household survey indicates that under-five malnutrition is higher than the national average within all socio-ecological systems, while adult malnutrition is slightly lower than the national average. Food diversity, particularly calorific and protein intake associated with fish and home-grown food production and consumption, is shown to be beneficial in reducing malnutrition. Although table salt is the highest contributor in daily consumption of sodium, salinity levels of domestic water sources show a correlation with hypertension, irrespective of age and gender, which is higher than the national average. These salinity levels are likely to increase over the twenty-first century.
This chapter explores the well-being of the coastal population of Bangladesh in relation to their ecosystem services, livelihoods, food consumption and health. This is achieved by exploring the specific nature of the association between human health and well-being with the provision of nutrition and food diversity by disaggregating elements of this relationship within the seven social-ecological systems (SESs) (see Chap. 22). The specific socio-economic and ecological service components of each SES are identified using data from the sampled household surveys (see, Chap. 23).
Human health and well-being status is closely linked with local ecosystem (see Chap. 7 and MEA 2003). However, the causal relation is complex and often hard to define as they are indirect, displaced in space and time and dependent on a number of modifying forces (Corvalan et al. 2005). The human–ecosystem interaction and how this interaction impacts health is yet to be properly understood or consequently used in policy level decision-making processes.
This work demonstrates how economic conditions, educational levels, environmental conditions and dietary intake differ across SESs and, in turn, is associated with differing health status. A key area of research is the impact of saline water intrusion across the SESs which has critical implications for health, with significant positive associations between hypertension and salinity in drinking water and dietary impact on under-five malnutrition.
Malnutrition: Malnutrition is a condition which results when a person’s diet fails to provide adequate nutrients for growth and maintenance or when a physical condition cannot utilise the food consumed due to illness. Malnutrition is observed as deficiencies such as thinness, stunting and micronutrient deficiencies, but also as overweight and obesity, known as overnutrition (UNICEF 2012). Under-five child malnutrition is assessed using the World Health Organization (WHO) child growth standard (Z-score) (WHO 2007). Adult health status is assessed using adult body mass index (BMI) category suggested for the Asian communities (Barba et al. 2004).
Hypertension: Respondent’s blood pressure is generated using the average value of last two readings of systolic and diastolic blood pressure. Thresholds for ‘normal’ are (i) systolic blood pressure (SBP) under 120 mmHg and (ii) the diastolic blood pressure (DBP) under 80 mmHg suggested by the American Heart Association (AHA 2016) and followed in national surveys (NIPORT et al. 2013).
Descriptive statistics are used to show the household characteristics and socio-demographic status of the study area. Health is assessed in terms of under-five child malnutrition and adult health status outcomes by prevalence of underweight, obesity and hypertension. Overall analysis considers explanatory variables of age, sex, educational status, wealth quintiles, seasons, structure of dwellings, occupation, dietary intake, landownership and salinity level in drinking water, and these are mapped across the different SESs. In all the graphs in this chapter, the SESs are listed in order according to the mean raw score of wealth index (poorest (left) to relatively less poor (right)1).
27.3 Results and Discussion
Malnutrition and hypertension prevalence was explored for the south-central and south-west coastal Bangladesh. Bivariate analysis is used to map the association between SESs for both under-five child malnutrition and adult malnutrition and hypertension.
27.3.1 Under-Five Child Malnutrition
To assess the malnutrition of under-five children, three main indices are used: (i) height-for-age (stunting), (ii) weight-for-height (wasting) and (iii) weight-for-age (underweight). In Bangladesh, the prevalence of stunting, wasting and underweight for under-five children is roughly 36, 14 and 33 per cent, respectively (NIPORT et al. 2016).
27.3.2 Adult Underweight, Overweight and Obesity
BMI is a critical indicator to understand adult nutritional status (Bailey and Ferro-Luzzi 1995). The household survey measured the anthropometry of males aged 18–54 years and females 15–49 years. To understand adult nutritional status, the standard measure, body mass index (BMI), is used to estimate the proportion of adults who are underweight, normal range, overweight or obese according to the health risk categories suggested for Asian communities by Barba et al. (2004): (i) underweight, BMI < 18.5 kg/m2 (thin or underweight); (ii) normal range, 18.5 kg/m2 ≤ BMI < 23 kg/m2 (increasing but acceptable risk); (iii) overweight, 23 kg/m2 ≤ BMI < 27.5 kg/m2 (increased risk) and (iv) obese, BMI ≥ 27.5 kg/m2 (higher risk). Health risks include the occurrence of hypertension, diabetes and cardiovascular disease.
Coastal population from both aquaculture SESs is at higher risk of malnutrition due to overweight and obesity, whereas people in the agriculture SESs are more at risk of being underweight. Along with poverty incidence and dietary intake, local livelihood pattern might have some significant impact on adult nutritional status. However, this will require further investigation to properly understand within the context of the ecosystem-based SES framework .
27.3.3 Adult Hypertension
The World Health Organisation (WHO) identifies hypertension as one of the most important causes of premature death worldwide (WHF 2017). Hypertension is diagnosed through blood pressure measurements. During the household survey, blood pressure of one eligible male and female was collected, and the average value of last two readings from the three readings of SBP and DBP was used to report respondent’s blood pressure as well as to maintain comparability with national statistics (NIPORT et al. 2013). The American Heart Association’s definition was used for classifying blood pressure: (i) normal (systolic blood pressure < 120 mmHg and diastolic blood pressure < 80 mmHg), (ii) pre-hypertensive (systolic blood pressure 120–139 mmHg or diastolic blood pressure 80–89 mmHg) and (iii) hypertensive (systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg) (AHA 2016).
Increased blood pressure associated with drinking water salinity has become an immerging public health concern in different parts of the world (Khan et al. 2014; Talukder et al. 2016). This is a concern in coastal Bangladesh, as about 80 per cent of coastal population depends on groundwater for drinking purpose (Shamsudduha 2013), a critical ecosystem service in this deltaic country.
For further analysis into the association between water salinity, blood pressure and age, drinking water salinity is divided into four categories by source and age into two categories. Firstly, sources of groundwater (tube well, stand post, public tap, etc.) are grouped under ‘tube well’ and all surface and other sources as ‘non-tube well’. As around 97 per cent of the national population depends on underground sources for drinking water (Shamsudduha 2013), the ‘tube-well’ category was then further divided using (i) the safe water limit (freshwater < 1000 mg/l) following the Bangladesh guideline of safe drinking water (Ahmed and Rahman 2000), (ii) slightly saline (1000–2000 mg/l) and (iii) moderate saline (≥ 2000 mg/l); the latter two categories based on expertise and judgement in the absence of an official standard. A high saline category (≥ 3000 mg/l) was initially created but, due to very limited number of samples, was combined with moderate category. Respondents (only eligible male and female 15–59, no children) were also divided into two age categories namely ‘below 35 (15–34 years, N = 2895; 46.6 per cent)’ and ‘35 and above (35–59 years, N = 3319; 53.4 per cent)’ to assess the hypertension prevalence in different age groups and also to compare with previous national studies.
Future salinity projections for coastal Bangladesh (see Chaps. 17, 18 and 28) indicate a localised increase in groundwater salinity by mid- and end of the century. This is likely to increase the risk of hypertension prevalence in coastal community unless there is proper policy intervention.
Overall, in the coastal area of Bangladesh, under-five child malnutrition is lower in some SESs than the national average. However, to some extent, the simple relationship between poverty and malnutrition is disrupted by access to fish and other diverse food groups. Food diversity, sufficient calorific and fish intake and domestically grown food from homestead gardening and consumption are shown to be beneficial against child malnutrition, with a clear indication that there needs to be between six and seven major food groups within the diet of children before a steep decline in malnutrition is identified.
Fish protein is shown to have a negative association with child malnutrition even where it replaces other sources of protein, thus universal fish consumption could have major benefits in terms of population health. While this is already recognised, this work offers the tangible evidence to support policies and interventions to ensure universal access to, and affordability of, protein sources (see Chap. 2).
In terms of adult malnutrition, women are more vulnerable than men in terms of both being under and overweight. Being overweight or obese is more prevalent in higher wealth quintile group and being underweight in the poorer groups.
Hypertension is higher in the delta region than nationally, even when accounting for age and gender. Though table salt is the highest contributor in daily consumption, saline drinking water is another key predictor of adult hypertension. It has been projected that, climate and environmental change will likely exacerbate saline water intrusion into drinking water sources (see Chap. 28). The results here suggest that adaptation interventions and planning for this increased risk could effectively include community sensitisation to salt consumption practices, given the underlying environmental exposure.
Along with poverty incidence, dietary diversity and salinity intake have significant impact on adult nutrition and ultimately on health status, underscoring the direct interaction between the ecosystem services and well-being outcomes .
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