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Focus on stroke: Shah Ebrahim – Changing states of risk

11 May, 2012

A geriatrician and stroke specialist by training, Professor Shah Ebrahim researches risk factors for cardiovascular disease and has a particular interest in prevention strategies. He splits his time between India and the UK, where he is Professor of Public Health at the London School of Hygiene and Tropical Medicine. Michael Regnier went to meet him.

In his office at the London School for Hygiene and Tropical Medicine, Professor Shah Ebrahim quotes Salman Rushdie’s The Satanic Verses over a cup of tea: “Paranoia, for the exile, is a prerequisite of survival.”

Shah Ebrahim

Shah Ebrahim

For Shah, this is an apt description of his own experience of going to live in India. “I’ve become very paranoid,” he admits. “You have to be constantly aware of what’s going on. But to what extent is it actually a safety mechanism to avoid getting into trouble, and at what point does your level of paranoia become a disease?”

I have come to talk to Shah about migration and how the effects it can have on health reveal important risk factors for conditions including cardiovascular diseases such as stroke. One difficulty of studying the effects of migration is that there is a selection factor at work. Though hard to define, it seems this selection factor may be heritable, as Shah explains he is not the first member of his family to change country.

“My grandfather migrated from India and he was so desperate to leave that he jumped ship. He was an illegal immigrant in Cape Town. Now, he had to be made of very different stuff to the rest of the family, who stayed behind in an impoverished bit of India in 1905 and were Muslim. The ones who were left behind inevitably were left behind not at random, but we can’t measure the effect of that selection.”

Nevertheless, Shah and his colleagues have studied health and economic migration within India, looking at people who moved from rural villages and found factory jobs in the city. As well as gathering data on the migrants, the study also included the migrants’ siblings still living in the village, their co-workers who were born and raised in the city, and their co-workers’ urban siblings who did not work in the factory. This design meant they could be confident that any differences they found were genuine effects of their migration and not caused by confounding factors such as genetics or early life experiences.

Results showed that levels of obesity, blood pressure and insulin resistance (a precursor of type 2 diabetes) in the migrant workers were closer to the high levels among their urban colleagues than the rural relatives’ low levels. “Twenty years after they migrated, men were more likely to have developed higher blood pressure and metabolic disturbances,” Shah adds, “but they did not gain as much weight as women who migrated. We think there are different pathways through which blood pressure and obesity are rising, probably related to alcohol – many Indian men drink heavily, although this is widely denied, but the women tend not to.”

Men are at greater risk of heart disease than women, but their risk of stroke is about the same. “There are several curious differences between these two cardiovascular diseases that share a lot of risk factors,” says Shah. “Among potentially complicated pathways, it can be difficult to know what is causing what, so we have to be very careful about the way we infer causality.

“Increasingly in epidemiology, we are looking for ways in which we can tease out effects that are difficult to be sure about in standard types of observational design – cross-sectional and cohort studies – because the patterns of confounding are very powerful. For example, there’s some literature on sleep and obesity that suggest short sleep makes you more likely to become obese and, therefore, have a greater risk of cardiovascular disease. But we know poverty is a strong risk factor for cardiovascular disease, for various reasons, and if you’re poor and you have an uncomfortable bed with an old sagging mattress, you may not sleep very well, so you need to adjust for that in your analysis.

“We did these analyses on sleep in our migration study and we found that between siblings, short sleep was bad for you in terms of body weight. But within sibling pairs, the difference disappeared – there was no impact of sleep duration, so differences in sleep duration did not correlate with one sibling being fatter than the other.”

Risk assessments

While sleep duration appears not to be one of them, several strong risk factors for cardiovascular disease have been identified, many of which can be modified with treatment or changes in behaviour. “Smoking and high blood pressure are powerful risk factors for stroke,” Shah explains. “We know this from the epidemiological evidence but also from randomised trials of drugs that lower blood pressure, which showed that treatment caused a drop in stroke risk. So we can say with total certainty that high blood pressure is a cause of stroke and treating it is a very good way of preventing stroke.”

The challenge for healthcare systems is to find the people who are at risk so they can be treated. “I only discovered my blood pressure when I was having a salivary gland chopped out,” Shah admits. “It kept getting blocked and would blow up to the size of my face every time I ate something tasty and salivated too much. When I was having my preoperative assessment, my blood pressure was 170/110, which is very high. Not a good level to have at all. Now it is at a normal level through treatment with antihypertensive drugs.”

Shah is leading a project to develop a new tool called mWellcare, which is intended to help incorporate preventive policies in basic healthcare, especially in developing countries. “We know that if you ask five pieces of information you can predict quite accurately the ten-year chance of having a heart attack or stroke,” he says. “The simplest question is ‘How old are you?’ Age is the biggest factor. Then smoking, blood pressure, and body weight or waist circumference. You can add in family history but most of the risk is already accounted for by those first few questions.

“So we know how to detect the problem, but we lack skilled people to do it in developing countries. One way to solve that is to skill people using mobile phone technology. It doesn’t require looking up tables, transcribing data, totting up scores or using a computer, which many healthcare workers won’t have in the developing world. But everyone has a mobile.”

The mWellcare project builds on technology already used to support some forms of HIV therapy – new suites of software will run on the existing platform. The result in the clinic will be a simple system that captures the necessary data and produces tailored guidance for the health worker to pass on to their patient.

Aggregated data can then be used to make comparisons between health centres or patients with different characteristics, or to track the prevalence of some risk factors over time. “The other valuable thing,” Shah adds, “is that it has the flexibility for the advice to change if new evidence emerges. If necessary, you could just reprogram every phone in every clinic rather than having to retrain all the workers.”

‘Primordial prevention’

Shah’s medical training took him into geriatrics – caring for the elderly – and a specialism in stroke. When asked what he’d like to see change in stroke services, he immediately replies that we need more and earlier prevention. “Detecting risk factors is the medical response to stroke,” he says. “However, the political response to epidemics of stroke and heart disease is singularly missing.

“The root causes of levels of blood pressure in a population have got nothing to do with whether or not we take antihypertensives. It’s not as if we all have ‘antihypertensive drug deficiency syndrome’. We have to ask why blood pressure is so high in some populations and quite low in others: it has a lot to do with the amount of salt in the diet and the amount of alcohol in the system, and these are modifiable. In the UK, we’ve taken the imaginative step of reducing salt in bread flour. Over five years, there will be about 15 to 20 per cent less salt in the British diet. It’s prevention by stealth: the bread tastes the same and everybody benefits.”

Shah is frustrated that there aren’t more policies to reduce the risk of cardiovascular disease in the population as a whole – ‘primordial prevention’, as it is sometimes called. “When people do get interested in these questions, there is a lot that can be done,” he says. “Fiscal, legal and policy changes have huge potential but they get much less attention than the latest blockbuster statin. It would have much more impact, it is eminently doable today – but it will take another ten years to persuade people to do it.”

Despite his frustrations, Shah retains his sense of humour. He tells of a German cardiologist who came up to him at a meeting. “He said to me, ‘Shah, you’re not interested in preventive cardiology, you want to prevent a cardiologist from earning a decent living!’ But whatever we do, these diseases are not going to disappear in the next 30, 40 or 50 years. I hope their incidence will decrease but as the population ages, the absolute numbers of people who will benefit from treatment will increase.

“It’s the avoidable disease of people at any age that’s the real tragedy,” he concludes, “and we could get rid of a lot of it – a third of it – with population-level interventions.”

Notes and references:

The Indian Migration Study was funded by the Wellcome Trust; the mWellcare project is funded through our R&D for Affordable Healthcare in India scheme, jointly supported by the Trust and the Indian Department of Biotechnology.

Ebrahim S, Kinra S, Bowen L, Andersen E, Ben-Shlomo Y, Lyngdoh T, Ramakrishnan L, Ahuja RC, Joshi P, Das SM, Mohan M, Davey Smith G, Prabhakaran D, Reddy KS, & Indian Migration Study group (2010). The effect of rural-to-urban migration on obesity and diabetes in India: a cross-sectional study. PLoS medicine, 7 (4) PMID: 20436961

This article is part of the Wellcome Trust’s Focus on stroke, a series of articles, interviews and videos running throughout May 2012, which is the Stroke Association’s Action on Stroke Month.

For more information on stroke, visit the Stroke Association’s site or call its helpline on 0303 303 3100. If you or someone with you is suspected of having a stroke, call the emergency services immediately.

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