Does smoking cause kidney disease?

The damaging  effects of smoking on lung and cardiovascular function are well known. Does smoking have similar effects on the kidney function as well? If yes, what is the evidence to support that conclusion?

Most recently, this question was addressed by two different studies, both of which were published in the Journal of the American Society of Nephrology. The first study I want to discuss came out from the Johns Hopkins University School of Medicine. Unlike a lot of its predecessor studies, this study was a prospective study (rather than a retrospective analysis of patients' charts), following about 23,000 patients over a span of 20 years. The results of this study clearly established that current cigarette smoking was a significant risk factor for development of chronic kidney disease (CKD). However, what was even more profound was that the attributable risk (difference in CKD rates between people who smoke and those who don't)  of CKD for smokers was 31%, which was even higher than hypertension as an isolated risk factor! It thus seemed to suggest that the damaging effect of smoking on kidney disease might have been related to factors beyond smoking's transient effect of increase in blood pressure alone. These conclusions applied both to women, and men.

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One year later, another study came out in the same journal, this time from Sweden.
This study echoed the above findings. It actually looked further in to the association between smoking, and two specific pathologic entities grouped under CKD (an umbrella term). These entities were nephrosclerosis (literally meaning hardening of the kidneys; this usually occurs from scarring in the kidney tissue and thickening of the blood vessels), and glomerulonephritis (again, an umbrella term for inflammation in the filtering apparatus of the kidney which can occur from multiple reasons). There seemed to be an associative trend between CKD, and a higher daily number of cigarettes smoked,  the number of years of smoking, and the total cumulative smoking dose. Smokers who have high blood pressure can expect to see a faster decline in their kidney function as well.  

Clearly, based on these, and other studies that I have not discussed, there seems to be a significant association between smoking and kidney disease. Smoking is already a well established risk factor for development of a type of kidney cancer called renal cell carcinoma (RCC). In fact, a full one-third of cases of RCC are thought to caused by smoking, with there also being a clear relationship between the number of cigarettes smoked and risk of development of RCC.  Finally, heavier smoking also increases the likelihood of advanced RCC (that is, cancer that has already spread to distant organs).

Last but not the least, we are well aware of the association between smoking and coronary heart disease. Coronary heart disease itself is an indirect but significant risk factor for kidney disease.

Ok, time to get a little preachy! It seems like a no-brainer that smoking is bad for your health. Quitting can reduce your risk of heart disease by as much as forty percent, besides doing wonders for your other health issues like cancer, lung disease, etc etc. At this time, however, it is not clear that quitting smoking will preserve or reverse the decline in kidney function, but there currently are studies addressing this question. This by no means implies that it is not worth quitting smoking, since the other health benefits are still worth dying (!) for.