End-stage renal disease and low level exposure to lead, cadmium and mercury; a population-based, prospective nested case-referent study in Sweden

Table 1 Baseline data on cases that later in life developed end-stage renal disease and referents

	Cases	Referents	Difference between cases and referents with 95% confidence intervals/p-value
Cases and referents from both study populations	118	347
Number of men/women	66/52	194/153
Northern Sweden Health and Disease Study (NSHDS)	72	214
Malmoe Diet and Cancer Study (MDCS)	46	133
Characteristics at base-line examination, i.e. prior to diagnosis of end-stage renal disease:
Diabetes (y/n)	20 (21%)	8 (3%)	OR = 8.3^a (3.5, 22)
Blood pressure (mm Hg), mean(standard deviation)
Systolic (SBP)	141 (21.3)	135 (19.9)	5.8 ^a (1.5, 10)
Diastolic (DBP)	85.8 (11.5)	83.1 (9.6)	2.7 ^a (0.42, 5.0)
Hypertension^b (y/n)	66 (54.6%)	125 (34.8%)	OR = 2.2^a (1.4, 3.5)
Smoking			p = 0.091^a
Never-smoker	34 (31%)	141 (41%)
Not current smoker (undefined ex-smoker or never-smoker)	11 (10%)	38 (11%)
Ex-smoker	26 (24%)	79 (23%)
Current smoker	39 (35%)	82 (24%)
Mean age at baseline^c (years)	63 (40–80)	63 (40–80)
Mean age at diagnosis of end-stage renal disease (years)	71 (46–87)
Time from baseline examination to development of end-stage renal disease (years)	7.7 (1–16)

OR=odds ratio.
^aDifferences in binary variables were expressed as ORs with 95% confidence intervals, continues variables as the difference with 95% confidence intervals, and p-values using the chi-square test were reported for categorical variables with more than two levels.
^bHypertension was defined as SBP >140 or DBP > 90 mm Hg, or antihypertensive medication at baseline.
^cmatching factor.