Defective kidneys may be a sign that traffic pollution is harming the arteries, research suggests.
Scientists who tested 1,100 stroke patients found a link between reduced kidney function and living close to a major road.
They believe kidney damage may be an indicator of artery disease due to long-term exposure to air pollution from road vehicles.
The patients, all admitted to hospital in the Boston area of Massachusetts, US, were tested for blood levels of creatinine, a by-product of muscle metabolism that should be filtered out of the body by the kidneys.
Creatinine in the blood provides an indication of kidney function known as estimated glomerular filtratrion rate (eGFR). If a person’s eGFR is low, it means the kidneys are not working properly.
Half the study participants lived within one kilometre of a major road, with the rest having homes between one and 10 kilometres away from heavy traffic.
Patients living closest to a major road had the lowest eGFR, the research showed. Compared with those living a kilometre away, people living 50 metres from a major road had a reduced eGFR equivalent to being four years older.
The kidney is especially vulnerable to damage caused by hard deposits building up on blood vessel walls, which can also lead to heart attacks and strokes.
Reduced kidney function seen in people living near roads is likely to be reflected in higher risks associated with heart and artery disease.
All the patients in the study had suffered ischaemic strokes, caused by artery damage reducing blood flow to the brain.
The researchers calculated that reducing living distance from a major road from one kilometre to 50 metres could increase the risk of cardiovascular death by four per cent and of death by all causes by one per cent.
Writing in the British Medical Journal, the authors led by Murray Mittleman, from Beth Israel Deaconess Medical Centre in Boston concluded: “The current study suggests that living near a major roadway is associated with lower eGFR in a cohort of patients presenting with acute ischaemic stroke.
“If causal, these results imply that exposures associated with living near a major roadway contribute to reduced renal (kidney) function, an important risk factor for cardiovascular events.”
British expert Tim Chico, of the University of Sheffield, said: “The importance of healthy kidneys is often overlooked, but many of the things that can damage the heart also affect these vital organs.
“Many people are unaware of the close link between heart and kidney disease, but problems with one often lead to problems with the other.
“Since we know traffic pollution increases the risk of heart disease, the message of this study – that traffic pollution might damage the kidneys – is perhaps to be expected.
“The responsibility to reduce traffic pollution falls on everyone and this study is yet another reason to travel on foot or bike where possible. “However, the current study only shows an ‘association’; it does not prove living next to road definitely affects kidney function.”