Snow property controls on modelled Ku-band altimeter estimates of first-year sea ice thickness: Case studies from the Canadian and Norwegian Arctic

Uncertainty in snow properties impacts the accuracy of Arctic sea ice thickness estimates from radar altimetry. On firstyear sea ice (FYI), spatiotemporal variations in snow properties can cause the Ku-band main radar scattering horizon to appear above the snow/sea ice interface. This can increase the estimated sea ice freeboard by several centimeters, leading to FYI thickness overestimations. This study examines the expected changes in Kuband main scattering horizon and its impact on FYI thickness estimates, with variations in snow temperature, salinity and density derived from 10 naturally occurring Arctic FYI Cases encompassing saline/non-saline, warm/cold, simple/complexly layered snow (4 cm to 45 cm) overlying FYI (48 cm to 170 cm). Using a semi-empirical modeling approach, snow properties from these Cases are used to derive layer-wise brine volume and dielectric constant estimates, to simulate the Ku-band main scattering horizon and delays in radar propagation speed. Differences between modeled and observed FYI thickness are calculated to assess sources of error. Under both cold and warm conditions, saline snow covers are shown to shift the main scattering horizon above from the snow/sea ice interface, causing thickness retrieval errors. Overestimates in FYI thicknesses of up to 65% are found for warm, saline snow overlaying thin sea ice. Our simulations exhibited a distinct shift in the main scattering horizon when the snow layer densities became greater than 440 kg/m3 , especially under warmer snow conditions. Our simulations suggest a mean Ku-band propagation delay for snow of 39%, which is higher than 25%, suggested in previous studies

Climate and the spread of COVID-19

Visual inspection of world maps shows that coronavirus disease 2019 (COVID-19) is less prevalent in countries closer to the equator, where heat and humidity tend to be higher. Scientists disagree how to interpret this observation because the relationship between COVID-19 and climatic conditions may be confounded by many factors. We regress the logarithm of confirmed COVID-19 cases per million inhabitants in a country against the country's distance from the equator, controlling for key confounding factors: air travel, vehicle concentration, urbanization, COVID-19 testing intensity, cell phone usage, income, old-age dependency ratio, and health expenditure. A one-degree increase in absolute latitude is associated with a 4.3% increase in cases per million inhabitants as of January 9, 2021 (p value < 0.001). Our results imply that a country, which is located 1000 km closer to the equator, could expect 33% fewer cases per million inhabitants. Since the change in Earth's angle towards the sun between equinox and solstice is about 23.5°, one could expect a difference in cases per million inhabitants of 64% between two hypothetical countries whose climates differ to a similar extent as two adjacent seasons. According to our results, countries are expected to see a decline in new COVID-19 cases during summer and a resurgence during winter. However, our results do not imply that the disease will vanish during summer or will not affect countries close to the equator. Rather, the higher temperatures and more intense UV radiation in summer are likely to support public health measures to contain SARS-CoV-2

Systolic blood pressure and 6-year mortality in South Africa: a country-wide, population-based cohort study

Background: Improving hypertension control is an important global health priority, yet, to our knowledge, there is no direct evidence on the relationship between blood pressure and mortality in sub-Saharan Africa. We aimed to investigate the relationship between systolic blood pressure and mortality in South Africa and to assess the comparative effectiveness of different systolic blood pressure targets for clinical care and population-wide hypertension management efforts. Methods: In this country-wide, population-based cohort study, we used longitudinal data on adults aged 30 years and older from five waves (2008, 2010–11, 2012, 2014–15, and 2017) of the South African National Income Dynamics Study. We estimated the relationship between systolic blood pressure and 6-year all-cause mortality and compared the mortality reductions associated with lowering systolic blood pressure to different targets (120 mm Hg, 130 mm Hg, 140 mm Hg, 150 mm Hg). We also estimated the mean blood pressure reduction required to achieve each target, the share of the population in need of management, and the number needed to treat (NNT) to avert one death under different hypothetical population-wide scale-up scenarios. Findings: Of the 8338 age-eligible respondents in the 2010–11 survey, 4993 had all required data and were included in our study. We found a weak, non-linear relationship between systolic blood pressure and 6-year mortality, with larger incremental mortality benefits at higher systolic blood pressure values: reducing systolic blood pressure from 160 mm Hg to 150 mm Hg was associated with a relative risk of mortality of 0·95 (95% CI 0·90 to 0·99; p=0·033), reducing systolic blood pressure from 150 mm Hg to 140 mm Hg had a relative risk of 0·96 (0·91 to 1·01; p=0·12), with no evidence of incremental benefits of reducing systolic blood pressure below 140 mm Hg. At the population level, reducing systolic blood pressure to 150 mm Hg among all those with a starting systolic blood pressure of more than 150 mm Hg was associated with the lowest NNT (n=50), 3·3 deaths averted (95% CI −0·6 to 0·3) per 1000 population, blood pressure management for 16% (95% CI 15·2 to 17·3) of individuals, and a −2·7 mm Hg mean change in systolic blood pressure required to achieve the 150 mm Hg scale-up target (−3·0 to −2·5; p<0·0001). Interpretation: The relationship between systolic blood pressure and mortality is weaker in South Africa than in high-income and many low-income and middle-income countries. As such, we do not find compelling evidence in support of targets below 140 mm Hg and find that scaling up management based on a 150 mm Hg target is more efficient in terms of the NNT compared with strategies to reduce systolic blood pressure to lower values. Funding: Non

The MONARCH intervention to enhance the quality of antenatal and postnatal primary health services in rural South Africa: protocol for a stepped-wedge cluster-randomised controlled trial

Background: Gaps in maternal and child health services can slow progress towards achieving the Sustainable Development Goals. The Management and Optimization of Nutrition, Antenatal, Reproductive, Child Health & HIV Care (MONARCH) study will evaluate a Continuous Quality Improvement (CQI) intervention targeted at improving antenatal and postnatal health service outcomes in rural South Africa where HIV prevalence among pregnant women is extremely high. Specifically, it will establish the effectiveness of CQI on viral load (VL) testing in pregnant women who are HIV-positive and repeat HIV testing in pregnant women who are HIV-negative. // Methods: This is a stepped-wedge cluster-randomised controlled trial (RCT) of 7 nurse-led primary healthcare clinics to establish the effect of CQI on selected routine antenatal and postnatal services. Each clinic was a cluster, with the exception of the two smallest clinics, which jointly formed one cluster. The intervention was applied at the cluster level, where staff received training on CQI methodology and additional mentoring as required. In the control exposure state, the clusters received the South African Department of Health standard of care. After a baseline data collection period of 2 months, the first cluster crossed over from control to intervention exposure state; subsequently, one additional cluster crossed over every 2 months. The six clusters were divided into 3 groups by patient volume (low, medium and high). We randomised the six clusters to the sequences of crossing over, such that both the first three and the last three sequences included one cluster with low, one with medium, and one with high patient volume. The primary outcome measures were (i) viral load testing among pregnant women who were HIV-positive, and (ii) repeat HIV testing among pregnant women who were HIV-negative. Consenting women ≥18 years attending antenatal and postnatal care during the data collection period completed outcome measures at delivery, and postpartum at three to 6 days, and 6 weeks. Data collection started on 15 July 2015. The total study duration, including pre- and post-exposure phases, was 19 months. Data will be analyzed by intention-to-treat based on first booked clinic of study participants. // Discussion: The results of the MONARCH trial will establish the effectiveness of CQI in improving antenatal and postnatal clinic processes in primary care in sub-Saharan Africa. More generally, the results will contribute to our knowledge on quality improvement interventions in resource-poor settings. // Trial registration: This trial was registered on 10 December 2015: www.clinicaltrials.gov, identifier NCT02626351

Hypertension and diabetes control along the HIV care cascade in rural South Africa

INTRODUCTION: Participation in antiretroviral therapy (ART) programmes has been associated with greater utilization of care for hypertension and diabetes in rural South Africa. The objective of this study was to assess whether people living with HIV on ART with comorbid hypertension or diabetes also have improved chronic disease management indicators. METHODS: The Health and Aging in Africa: a longitudinal study of an INDEPTH Community in South Africa (HAALSI) is a cohort of 5059 adults >40 years old. Enrollment took place between November 2014 and November 2015. The study collected population-based data on demographics, healthcare utilization, height, weight, blood pressure (BP) and blood glucose as well as HIV infection, HIV-1 RNA viral load (VL) and ART exposure. We used regression models to determine whether HIV care cascade stage (HIV-negative, HIV+ /No ART, ART/Detected HIV VL, and ART/Undetectable VL) was associated with diagnosis or treatment of hypertension or diabetes, and systolic blood pressure and glucose among those with diagnosed hypertension or diabetes. ART use was measured from drug level testing on dried blood spots. RESULTS AND DISCUSSION: Compared to people without HIV, ART/Undetectable VL was associated with greater awareness of hypertension diagnosis (adjusted risk ratio (aRR) 1.18, 95% CI: 1.09 to 1.28) and treatment of hypertension (aRR 1.24, 95% CI: 1.10 to 1.41) among those who met hypertension diagnostic criteria. HIV care cascade stage was not significantly associated with awareness of diagnosis or treatment of diabetes. Among those with diagnosed hypertension or diabetes, ART/Undetectable VL was associated with lower mean systolic blood pressure (5.98 mm Hg, 95% CI: 9.65 to 2.32) and lower mean glucose (3.77 mmol/L, 95% CI: 6.85 to 0.69), compared to being HIV-negative. CONCLUSIONS: Participants on ART with an undetectable VL had lower systolic blood pressure and blood glucose than the HIV-negative participants. HIV treatment programmes may provide a platform for health systems strengthening for cardiometabolic disease

Quasi-experimental study designs series—paper 4: uses and value

Quasi-experimental studies are increasingly used to establish causal relationships in epidemiology and health systems research. Quasi-experimental studies offer important opportunities to increase and improve evidence on causal effects: (i) they can generate causal evidence when randomized controlled trials are impossible; (ii) they typically generate causal evidence with a high degree of external validity; (iii) they avoid the threats to internal validity that arise when participants in non-blinded experiments change their behavior in response to the experimental assignment to either intervention or control arm (such as compensatory rivalry or resentful demoralization); (iv) they are often well-suited to generate causal evidence on long-term health outcomes of an intervention, as well as non-health outcomes such as economic and social consequences; and (v) they can often generate evidence faster and at lower cost than experiments and other intervention studies

Association between country preparedness indicators and quality clinical care for cardiovascular disease risk factors in 44 lower- and middle-income countries:A multicountry analysis of survey data

BackgroundCardiovascular diseases are leading causes of death, globally, and health systems that deliver quality clinical care are needed to manage an increasing number of people with risk factors for these diseases. Indicators of preparedness of countries to manage cardiovascular disease risk factors (CVDRFs) are regularly collected by ministries of health and global health agencies. We aimed to assess whether these indicators are associated with patient receipt of quality clinical care.Methods and findingsWe did a secondary analysis of cross-sectional, nationally representative, individual-patient data from 187,552 people with hypertension (mean age 48.1 years, 53.5% female) living in 43 low- and middle-income countries (LMICs) and 40,795 people with diabetes (mean age 52.2 years, 57.7% female) living in 28 LMICs on progress through cascades of care (condition diagnosed, treated, or controlled) for diabetes or hypertension, to indicate outcomes of provision of quality clinical care. Data were extracted from national-level World Health Organization (WHO) Stepwise Approach to Surveillance (STEPS), or other similar household surveys, conducted between July 2005 and November 2016. We used mixed-effects logistic regression to estimate associations between each quality clinical care outcome and indicators of country development (gross domestic product [GDP] per capita or Human Development Index [HDI]); national capacity for the prevention and control of noncommunicable diseases ('NCD readiness indicators' from surveys done by WHO); health system finance (domestic government expenditure on health [as percentage of GDP], private, and out-of-pocket expenditure on health [both as percentage of current]); and health service readiness (number of physicians, nurses, or hospital beds per 1,000 people) and performance (neonatal mortality rate). All models were adjusted for individual-level predictors including age, sex, and education. In an exploratory analysis, we tested whether national-level data on facility preparedness for diabetes were positively associated with outcomes. Associations were inconsistent between indicators and quality clinical care outcomes. For hypertension, GDP and HDI were both positively associated with each outcome. Of the 33 relationships tested between NCD readiness indicators and outcomes, only two showed a significant positive association: presence of guidelines with being diagnosed (odds ratio [OR], 1.86 [95% CI 1.08-3.21], p = 0.03) and availability of funding with being controlled (OR, 2.26 [95% CI 1.09-4.69], p = 0.03). Hospital beds (OR, 1.14 [95% CI 1.02-1.27], p = 0.02), nurses/midwives (OR, 1.24 [95% CI 1.06-1.44], p = 0.006), and physicians (OR, 1.21 [95% CI 1.11-1.32], p ConclusionIn this study, we observed that indicators of country preparedness to deal with CVDRFs are poor proxies for quality clinical care received by patients for hypertension and diabetes. The major implication is that assessments of countries' preparedness to manage CVDRFs should not rely on proxies; rather, it should involve direct assessment of quality clinical care

The state of hypertension care in 44 low-income and middle-income countries:a cross-sectional study of nationally representative individual-level data from 1·1 million adults

Evidence from nationally representative studies in low-income and middle-income countries (LMICs) on where in the hypertension care continuum patients are lost to care is sparse. This information, however, is essential for effective targeting of interventions by health services and monitoring progress in improving hypertension care. We aimed to determine the cascade of hypertension care in 44 LMICs-and its variation between countries and population groups-by dividing the progression in the care process, from need of care to successful treatment, into discrete stages and measuring the losses at each stage. In this cross-sectional study, we pooled individual-level population-based data from 44 LMICs. We first searched for nationally representative datasets from the WHO Stepwise Approach to Surveillance (STEPS) from 2005 or later. If a STEPS dataset was not available for a LMIC (or we could not gain access to it), we conducted a systematic search for survey datasets; the inclusion criteria in these searches were that the survey was done in 2005 or later, was nationally representative for at least three 10-year age groups older than 15 years, included measured blood pressure data, and contained data on at least two hypertension care cascade steps. Hypertension was defined as a systolic blood pressure of at least 140 mm Hg, diastolic blood pressure of at least 90 mm Hg, or reported use of medication for hypertension. Among those with hypertension, we calculated the proportion of individuals who had ever had their blood pressure measured; had been diagnosed with hypertension; had been treated for hypertension; and had achieved control of their hypertension. We weighted countries proportionally to their population size when determining this hypertension care cascade at the global and regional level. We disaggregated the hypertension care cascade by age, sex, education, household wealth quintile, body-mass index, smoking status, country, and region. We used linear regression to predict, separately for each cascade step, a country's performance based on gross domestic product (GDP) per capita, allowing us to identify countries whose performance fell outside of the 95% prediction interval. Our pooled dataset included 1 100 507 participants, of whom 192 441 (17·5%) had hypertension. Among those with hypertension, 73·6% of participants (95% CI 72·9-74·3) had ever had their blood pressure measured, 39·2% of participants (38·2-40·3) had been diagnosed with hypertension, 29·9% of participants (28·6-31·3) received treatment, and 10·3% of participants (9·6-11·0) achieved control of their hypertension. Countries in Latin America and the Caribbean generally achieved the best performance relative to their predicted performance based on GDP per capita, whereas countries in sub-Saharan Africa performed worst. Bangladesh, Brazil, Costa Rica, Ecuador, Kyrgyzstan, and Peru performed significantly better on all care cascade steps than predicted based on GDP per capita. Being a woman, older, more educated, wealthier, and not being a current smoker were all positively associated with attaining each of the four steps of the care cascade. Our study provides important evidence for the design and targeting of health policies and service interventions for hypertension in LMICs. We show at what steps and for whom there are gaps in the hypertension care process in each of the 44 countries in our study. We also identified countries in each world region that perform better than expected from their economic development, which can direct policy makers to important policy lessons. Given the high disease burden caused by hypertension in LMICs, nationally representative hypertension care cascades, as constructed in this study, are an important measure of progress towards achieving universal health coverage. Harvard McLennan Family Fund, Alexander von Humboldt Foundation