Exposure to second-hand smoke is associated with a greater risk of developing chronic kidney disease (CKD), say Korean researchers who divided 131,196 never-smokers into three groups:

• No exposure to second-hand smoke
• Exposed on fewer than three days a week
• Exposed on at least three days a week.

CKD was defined as estimated glomerular filtration rate below 60ml/min per 1.73m2.

Subjects were aged, on average, 53 years and 74 per cent were not exposed to second-hand smoke. About 2 per cent of patients had CKD at baseline. The risk of CKD was 72 per cent higher in those exposed to second-hand smoke on fewer than three days a week and 44 per cent higher in those exposed on at least three days a week compared with controls.

The authors followed 1,948 people without CKD at baseline for a mean of 104 months. During this time, 16 per cent developed CKD. The risk of developing CKD was 59 per cent higher in those exposed to second-hand smoke on fewer than three days a week and 66 per cent higher in those exposed on at least three days a week compared with controls.

This study has limitations. For example, questionnaires rather than direct measurements determined exposure to second-hand smoke and the authors could not ascertain which patients received drugs that potentially protected or harmed the kidneys.

In addition, the authors did not measure accumulation of second-hand toxins from smoke. Despite all this, they conclude that “exposure to second-hand smoke was significantly associated with higher risk of CKD development”.