With great (statistical) power comes great responsibility

Tessa Strain and Søren Brage

We are all familiar with studies that investigate the associations between physical activity and outcomes such as death or cardiovascular disease. However, we rarely focus on the length of time over which these study participants are followed up to see if one of the outcomes occurs.

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Childhood diarrhoeal illness may be underestimated in national health surveys

Katie Overbey, Kellogg Schwab and Natalie Exum

For children in low-income countries, diarrhoea remains a major cause of death and can lead to long-term health consequences. Accurate estimates of childhood diarrhoeal illness are crucial to evaluating the success of campaigns to defeat diarrhoea and improve health in countries where the burden of diarrhoea is high.

In our study, recently published in the IJE, we found that caregivers may underestimate diarrhoeal diseases in children aged under 5 years when asked to recall whether the children had diarrhoea in the previous 2 weeks. Compared with a 1-week recall period, there was a consistent underestimation of the prevalence of diarrhoea across five countries in sub-Saharan Africa.

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Take my breath away: India’s crop residue burning affects respiratory health

Suman Chakrabarti, Md Tajuddin Khan and Samuel Scott

Respiratory infections are the most common chronic disease in children globally and a leading cause of death in developing countries. This situation is exacerbated by air pollution.

Air pollution in northern India, mainly New Delhi and the neighbouring states, is exacting a toll on the health of residents, making global headlines and highlighting the severity and extent of this public health disaster in one of the world’s fastest-growing economies.

A contributory factor to air pollution in northern India is the harmful practice of crop residue burning — when farmers burn the crop residue to clear fields before sowing a new crop. Although banned by the Indian government in 2015, this practice remains prevalent in many parts of the northern Indian states of Punjab, Haryana and Uttar Pradesh.

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Did you know that adults with chronic disease in the UK are markedly less active than their healthy peers?

Terence Dwyer

Over an average week, adults in the United Kingdom living with chronic disease spend 61 minutes (9%) less on moderate activity — such as gardening, brisk walking and housework — and 3 minutes (11%) less on vigorous activity — such as running and aerobics — than their healthy peers.

Perhaps this comes as a surprise. After all, few of us would question the health benefits of keeping moving and getting our heart rate racing. Physical activity guidelines, such as those developed by the UK’s National Institute for Health and Clinical Excellence, specifically refer to the importance of increasing physical activity for chronic disease management.

So why have we observed a gap in activity levels between those living with chronic disease and those without?

Continue reading “Did you know that adults with chronic disease in the UK are markedly less active than their healthy peers?”

Is it time to establish breast cancer as a smoking-related cancer?

Inger T Gram

Smoking was established as a cause of lung cancer in the late 1950s. It then took another 50 years to establish that colorectal cancer was also a smoking-related cancer. However, as of 2018, a causal relationship between smoking and breast cancer had not yet been established. It may seem strange that it is taking so long to prove that smoking is a cause of all three of the most common cancers globally. Breast and lung cancer each account for 2.09 million cases annually and colorectal cancer for 1.8 million.

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Circulating cotinine concentrations and lung cancer risk evaluated in 20 international cohorts

Tricia L Larose, Arnulf Langhammer and Mattias Johansson, for the Lung Cancer Cohort Consortium (LC3)

Lung cancer is one of the most common cancers worldwide, accounting for 2.09 million cases and 1.76 million deaths in 2018. Two of the most prolific cancer epidemiologists of our time — Sir Richard Doll and Sir Bradford Hill — identified smoking as the biggest cause of lung cancer in their seminal report, “Smoking and Carcinoma of the Lung”, published in the British Medical Journal in 1950. Nearly 70 years later, smoking remains the predominant risk factor for lung cancer, as well as for 15 additional cancers and other non-communicable diseases.

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Hygiene gaps: between access and practice, and from region to region

Jennyfer Wolf, Richard Johnston, Matthew C Freeman and Annette Prüss-Ustün

Handwashing with soap after faecal contact is key to preventing disease and death from enteric infectious diseases. Our study, recently published in the IJE, is the first to provide global, regional and country estimates of handwashing with soap after potential contact with human faeces, based on representative data on access to handwashing facilities collected for monitoring of the Sustainable Development Goals (SDGs). Our results show that handwashing with soap after using the toilet or other potential contact with human faeces is poorly practised worldwide and that even the necessary equipment – handwashing facilities with soap and water – are inaccessible to billions of people.

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What are the long-term health effects of earthquakes? Meta-analysis results and implications for epidemiological practice

Alba Ripoll Gallardo, Barbara Pacelli and Elias Allara


Population growth and urbanisation of seismic areas are leading to a constant increase in the health-related and economic toll of earthquakes. In 2014 alone, 324 natural disasters were reported worldwide, resulting in 141 million casualties and nearly $100 billion in damage. Geophysical disasters, including earthquakes, accounted for about 10% of these events.

Although the impact of earthquakes in the response phase – that is, immediately or shortly after the main seismic event – has been well studied, we have little knowledge of the effects of earthquakes in the medium and long term. This uncertainty may cause inefficient planning of post-earthquake epidemiological surveillance, resulting in potential underestimation of public health needs.

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Lower risk of cerebral palsy in the child if the parents have higher education

Ingeborg Forthun

Ingeborg Forthun

Cerebral palsy is the most common physical disability among children, with about two per 1000 live-born infants being diagnosed with the disorder. In most children with cerebral palsy, the disability is caused by damage to the immature brain during pregnancy or birth that results in problems with movement.

Denmark and Norway have low income inequality and free access to education and offer high-quality antenatal care to pregnant women free of charge. Nevertheless, in our study recently published in the International Journal of Epidemiology, we found that the risk of having a child with cerebral palsy in these two countries varies by the parents’ educational level, and this educational gradient has been surprisingly stable over time.

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Does correcting for bias caused by unequal survival in the treatment arms of a randomised controlled trial matter?

Anwar T Merchant and Bryn E Davis

Merchant Davis

The Obstetrics and Periodontal Therapy (OPT) Study was an NIH-funded randomised controlled trial designed to evaluate whether periodontal treatment in pregnant women had any effect on preterm birth; its findings were published in 2006. The investigators randomly assigned about 800 women who had been pregnant for less than 16 weeks, and had periodontal disease, to one of two groups. One group received periodontal treatment during pregnancy, whereas the other group received treatment after pregnancy.

Although the study found that treatment controlled periodontal infection and reduced the microorganism load, there was no difference in preterm birth rates between the two groups. The investigators concluded that treating periodontal disease during pregnancy did not affect the risk of preterm birth. However, they also found that there were more stillbirths in the group that received treatment after pregnancy, suggesting that periodontal treatment may improve survival of fetuses. The potential bias resulting from the intervention affecting both the outcome (in this case, preterm birth) and survival (in this case, stillbirth) was acknowledged as a limitation.

Continue reading “Does correcting for bias caused by unequal survival in the treatment arms of a randomised controlled trial matter?”