Does using SNAP harm cognitive health? Why we should care about better analytical methods

Matthew C Lohman, Anwar T Merchant and Catherine Y Chi

The Supplemental Nutrition Assistance Program (SNAP) is an initiative that provides food benefits to low-income Americans to help them afford groceries. Claims that use of SNAP contributes to bad health outcomes appear often in research and the media. Some studies have found that people who use SNAP have worse diet quality, higher bodyweight and poorer cognitive performance than those who don’t. Such findings are sometimes used, implicitly or explicitly, to justify more restrictive eligibility rules, work requirements or other policies that could reduce access to the program.

But a closer look at the evidence suggests we should be more cautious in how we interpret it. Our recent study in the International Journal of Epidemiology found that, by using methods designed to deal with hidden bias, apparent relationships between SNAP use and negative outcomes like cognitive decline largely disappear.

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Are generations ageing less healthily over time? Multimorbidity trends in Catalonia, Spain

Iñaki Permanyer, Jordi Gumà-Lao, Sergi Trias-Llimós and Aïda Solé-Auró

Multimorbidity – where someone has two or more chronic health conditions at the same time – is a growing challenge facing health care systems, particularly in countries with low mortality rates. Although much is known about multimorbidity, important questions remain unanswered. Is it occurring more often just because people are living longer? What are the patterns of disease onset across different generations? Are some generations getting multiple chronic diseases more rapidly than others?

In an increasingly long-lived population, it’s essential for anticipating future pressures on health systems to assess whether improvements in survival prospects are accompanied by declines in illness, or whether these gains in longevity are coming at the cost of more disease and infirmity and greater care needs.

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Counting the true toll of the COVID-19 pandemic in New Zealand

Michael Plank

How many people died because of the COVID-19 pandemic in New Zealand? It sounds like a simple question, but the answer depends on more than just counting reported COVID-19 deaths.

In our recent study, published in the International Journal of Epidemiology, we looked at a key statistic called excess mortality – the number of deaths above what we would have expected if there hadn’t been a pandemic. Excess mortality helps us to measure the overall impact of the pandemic, not just from COVID-19 itself but also from things like delayed medical care or the side effects of lockdowns.

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Is rapid growth after birth linked to improved intelligence in children who had poor fetal growth?

Yi Ying Ong, Nicholas Beng Hui Ng and Yung Seng Lee

Imagine two babies born at full term. Baby A had a normal growth rate in the womb but is born naturally small, while Baby B is born small after their growth in the womb slowed down. Baby B’s “fetal growth deceleration” may have been caused by placental issues or other conditions limiting the baby’s nutrient and oxygen supply, potentially affecting their brain development. Research studies have often lumped Baby A and Baby B together under the categories of “low birthweight” or “small for gestational age”, but these conditions are different from slowed fetal growth. As such, it remains unclear how fetal growth deceleration affects children’s cognitive abilities. 

Now, let’s look at what happens after birth — some believe that if Baby B’s growth catches up, it might compensate for the earlier growth problems and support better brain development. But is this true?

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Overadjustment – an important bias hiding in plain sight

Anita van Zwieten, Fiona M Blyth, Germaine Wong and Saman Khalatbari-Soltani

Epidemiologists are generally well equipped to design and conduct studies that minimise various types of bias, so as to obtain the most accurate estimates possible and therefore high-quality evidence. In observational studies, some types of bias, like confounding, have received a lot of attention, while others have been overlooked. One that has been neglected is overadjustment bias, which occurs when researchers adjust for an explanatory variable on the causal pathway from exposure to outcome when seeking to estimate the total effect.

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Proposing a new indicator to assess health disparities: measuring inequalities in causes of death

Iñaki Permanyer and Júlia Almeida Calazans

Policymakers and scholars are increasingly interested in monitoring and curbing health inequalities. Much is known about the main causes of death and how mortality has been shifting from most deaths around the world being caused by communicable diseases towards most being due to non-communicable causes.

However, less is known about the heterogeneity in these causes of death. Are people in some countries dying from an increasingly varied set of causes? Measuring how ‘similar’ or ‘dissimilar’ the different causes of death are can help us understand global health inequalities and patterns of mortality.

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Why we need a new measure of maternal health: the “lifetime risk of maternal near miss”

Ursula Gazeley

According to the most recent data from the World Health Organization, the lifetime risk of maternal death for a girl in Chad is a staggering 1 in 15, compared with 1 in 43,000 in Norway. This means that a girl in Chad has an almost 3000 times greater risk of dying from a maternal cause during her reproductive lifetime than a girl in Norway. The lifetime risk of maternal death is a useful measure to help us understand this global inequality in maternal mortality.

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Have smartphones and ubiquitous internet access affected sedentary time among children and adolescents?

Jakob Tarp, Knut Eirik Dalene and Ulf Ekelund

As will be obvious to anyone on a bus or train or waiting for coffee, access to screen-based media has been revolutionised over the past two decades. In 2020, there were more than six billion smartphone users worldwide and almost global penetration. Yet, our understanding of how these devices have affected other behaviour, such as sedentary time, is limited.

In our study, recently published in the IJE, we used accelerometer measurements of sedentary time collected for the Norway-wide physical activity monitoring system to estimate that a 9-year-old boy or 15-year-old girl or boy spent, on average, 20 to 30 minutes more each day being sedentary in 2018 than in 2005. We also found that children and adolescents accumulate more of their sedentary time in longer uninterrupted periods, compared with a more fragmented pattern of activity in 2005. Children and adolescents now spend less time sitting for short periods of 5 minutes or less at a time.

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Regular exercise, even in polluted areas, can lower risk of cancer mortality

Yacong Bo and Xiang Qian Lao

Regular exercise is recognised as providing significant lifestyle-related protection against non-communicable diseases. It can also reduce the likelihood of cardiovascular disease, cancer and premature death. By contrast, long-term exposure to fine particulate matter (PM2.5) can increase the likelihood of respiratory and cardiovascular disease and certain cancers, leading to premature death.

Outdoor exercise might increase the inhalation and deposition of air pollutants, potentially counteracting its beneficial effects. Evaluation of this risk–benefit relationship has become an important public health concern because more than 91% of the global population lives in areas where air quality fails to meet the 2005 World Health Organization guidelines.

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Could biomass fuel use perpetuate the poverty trap through cardiovascular disease and all-cause mortality?

Shuyi Qiu and John S Ji

Many people around the world are still using biomass as a fuel for cooking and heating. Inefficient combustion of solid fuels is the primary cause of indoor household air pollution, estimated to be responsible for 4.3 million premature deaths in 2012 (7.7% of total mortality).

The World Health Organization’s latest global air quality guidelines point out that indoor air pollution causes a health burden that mostly affects people in low- and middle-income countries. Many global development agencies are working with governments of developing countries to reduce household air pollution. For example, China’s Relocation Program in the poorest provinces is a significant part of China’s poverty eradication plans. This large-scale program relocates millions of residents in absolute poverty to places with better living conditions, including fuel type.

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