Smoking and diabetic nephropathy: An updated systematic review and meta-analysis.

Objectives: Several studies have reported the potential association between smoking and diabetic nephropathy. However, the studies of non-significant association results were against the association between smoking and diabetic nephropathy. Therefore, the relationship between smoking and diabetic nephropathy was still debated and controversial.

Methods: Prospective cohort studies were included in the current meta-analysis. The tobacco smoking (current smokers or former smokers) and non-smoking groups in the enrolled studies were compared for the hazard ratio (HR) of diabetic nephropathy. Fifteen studies with 221,821 subjects were included in this meta-analysis. Subgroup analysis of the type 1 diabetes and type 2 diabetes groups was also performed individually to investigate the effects of different types of diabetes on the relationship between smoking and diabetic nephropathy.

Results: Current smoking was significantly associated with a greater log HR of diabetic nephropathy [1.44 (1.22-1.70), Z = 4.39]. In addition, former smoking was significantly associated with diabetic nephropathy [log HR = 1.04 (1.03-1.05), Z = 8.02]. The individual subgroup analysis of type 1 diabetes and type 2 diabetes subjects showed that smoking might be both significantly associated with greater log HRs of diabetic nephropathy.

Discussion: Current and former smoking might be the risk factors for diabetic nephropathy in the current meta-analytic results. The phenomenon of such significant associations were discovered in type 1 and 2 diabetes.