Introduction 1 3 3 4 1 5 6 7 8 10 11 12 13 14 15 16 16 12 17 18 19 17 20 21 Methods The Rotterdam Study 22 Assessment of diet 23 24 Clinical examination 25 Assessment of sodium and potassium excretion ® Follow-up procedures International Classification of Diseases, 10th revision 26 Myocardial infarction comprised ICD-10 code I21 and stroke comprised ICD-10 codes I60-I67. Both fatal and non-fatal incident events were recorded. For the present study, only first events were considered. Events followed by death within 28 days were classified as fatal. CVD mortality comprised fatal myocardial infarction, fatal stroke, sudden cardiac death and other forms of fatal CVD (ICD-10 codes I20-I25, I46, I49, I50, I60-I67, I70-I74, and R96). Study population n  n  n  23 n Data analysis Pearson correlations were computed to examine inter-relationships between urinary and dietary measures of electrolyte intake and associations with total energy intake. 27 28 P 2 2 Also in the sub-cohort free of CVD and hypertension, the distribution of 24-h urinary sodium excretion was divided into quartiles to be able to examine the relationship with all-cause mortality at extreme intakes. Quartiles of urinary sodium (cut-off levels: 66, 105 and 151 mmol/24 h) were entered categorically into the fully adjusted model (model 3), using the lower quartile as the reference. Results 1 n  Table 1 Baseline characteristics of the study population  Random sample Cases Incident MI Incident stroke CVD mortality All-cause mortality No. of subjects 1,448 206 181 217 795 In random sample (%)  31 31 28 29 Age (year) 69.2 (8.7) 71.0 (8.0) 74.0 (8.5) 76.8 (8.4) 76.9 (8.9) Men (%) 41 62 45 51 49 2 26.4 (3.8) 26.3 (3.4) 26.0 (3.3) 26.2 (3.8) 25.7 (3.8) a     Current 23 29 28 23 26     Former 41 48 42 47 40     Never 36 23 29 29 35 Alcohol use (%) 81 74 80 71 73 a,b     Low 58 61 60 65 66     Intermediate 32 31 34 30 28     High 10 8 6 5 6 Serum cholesterol (mmol/l)     Total 6.6 (1.2) 6.3 (1.3) 6.5 (1.2) 6.6 (1.4) 6.3 (1.3)     HDL 1.4 (0.4) 1.3 (0.4) 1.3 (0.4) 1.2 (0.4) 1.3 (0.4) Blood pressure (mmHg)     Systolic 140 (22) 145 (23) 149 (24) 146 (25) 145 (25)     Diastolic 74 (11) 74 (12) 75 (13) 73 (13) 73 (14) c 37 44 53 55 47 d 10 21 22 26 21 e 17 35 17 39 28 Values are means with standard deviations, or percentages; CVD, cardiovascular disease; MI, myocardial infarction a b c d e 2 P Table 2 Baseline urinary excretions and dietary intakes of Dutch men and women aged 55 years and over: The Rotterdam Study  Random subcohort Cases Incident MI Incident stroke CVD mortality All-cause mortality Urinary excretion a Volume (l/24 h) 1.4 (0.6) 1.4 (0.6) 1.4 (0.6) 1.3 (0.6) 1.3 (0.6) Sodium (mmol/24 h) 117 (69) 124 (68) 115 (72) 99 (61) 107 (66) Potassium (mmol/24 h) 45 (22) 47 (22) 45 (23) 44 (24) 44 (22) Sodium/potassium 2.8 (1.5) 2.7 (1.3) 2.7 (1.3) 2.5 (1.4) 2.6 (1.6) Creatinine (mmol/24 h) 9.2 (4.9) 9.8 (4.7) 8.4 (4.4) 8.1 (4.7) 8.1 (4.4) Sodium/creatinine 13.8 (6.6) 13.6 (6.1) 14.6 (7.1) 14.0 (8.0) 14.8 (7.9) Potassium/creatinine 5.4 (2.2) 5.3 (2.1) 5.8 (2.1) 6.1 (2.6) 6.1 (2.5) Dietary intake b Total energy (mJ/day) 8.3 (2.1) 8.6 (2.2) 8.4 (2.2) 8.3 (2.0) 8.5 (2.2) Saturated fat (g/day) 32 (12) 34 (13) 34 (13) 33 (13) 34 (12) Calcium (g/day) 1.1 (0.4) 1.1 (0.4) 1.1 (0.4) 1.1 (0.5) 1.1 (0.4) c 2.2 (0.7) 2.3 (0.6) 2.2 (0.6) 2.2 (0.7) 2.2 (0.7) Potassium (g/day) 3.6 (0.8) 3.7 (0.8) 3.6 (0.8) 3.6 (0.9) 3.6 (0.9) Values are means with standard deviations; CVD, cardiovascular disease; MI, myocardial infarction a b c 3 2 Table 3 Relative risk of urinary sodium with cardiovascular events and all-cause mortality in Dutch men and women aged 55 years and over  a a Incident MI b 1.13 (0.95–1.34) 1.04 (0.75–1.43) c 1.16 (0.98–1.39) 1.07 (0.77–1.50) d 1.19 (0.97–1.46) 1.14 (0.77–1.69) Incident stroke RR, model 1 1.09 (0.89–1.33) 1.16 (0.84–1.61) RR, model 2 1.09 (0.87–1.35) 1.15 (0.81–1.62) RR, model 3 1.08 (0.80–1.46) 1.02 (0.66–1.58) CVD mortality e RR, model 1 0.74 (0.60–0.91) 0.84 (0.59–1.22) RR, model 2 0.83 (0.68–1.02) 0.95 (0.66–1.39) RR, model 3 0.77 (0.60–1.01) 0.83 (0.47–1.44) All-cause mortality RR, model 1 0.90 (0.81–1.02) 1.00 (0.83–1.20) RR, model 2 0.96 (0.84–1.09) 1.10 (0.91–1.34) RR, model 3 0.95 (0.81–1.12) 1.12 (0.86–1.46) RR, Relative risk with 95% confidence interval per standard deviation increase in urinary sodium (mmol/24 h), obtained by Cox proportional hazard analysis a 1 b c d e 4 Table 4 Relationship of urinary and dietary potassium with cardiovascular events and all-cause mortality in Dutch men and women aged 55 years and over  a a Urinary excretion (mmol/24 h) Dietary intake (mg/day) Urinary excretion (mmol/24 h) Dietary intake (mg/day) Incident MI b 1.10 (0.89–1.35) 0.98 (0.85–1.13) 1.15 (0.84–1.59) 1.14 (0.85–1.54) c 1.16 (0.94–1.43) 0.94 (0.81–1.09) 1.25 (0.94–1.74) 1.07 (0.78–1.46) d 1.11 (0.87–1.43) 0.90 (0.65–1.24) 1.22 (0.79–1.87) 1.32 (0.65–2.67) Incident stroke RR, model 1 1.09 (0.87–1.36) 0.99 (0.84–1.17) 1.12 (0.79–1.60) 1.07 (0.79–1.43) RR, model 2 1.12 (0.89–1.42) 0.99 (0.84–1.16) 1.15 (0.77–1.71) 1.20 (0.86–1.68) RR, model 3 1.17 (0.86–1.58) 1.02 (0.71–1.46) 1.11 (0.61–2.04) 1.06 (0.50–2.29) CVD mortality e RR, model 1 1.13 (0.90–1.41) 0.97 (0.82–1.14) 1.63 (1.14–2.33) 1.23 (0.83–1.84) RR, model 2 1.14 (0.92–1.42) 0.95 (0.81–1.12) 1.66 (1.08–2.56) 1.19 (0.78–1.83) RR, model 3 1.23 (0.94–1.60) 0.97 (0.72–1.31) 1.45 (0.84–2.54) 1.43 (0.67–3.03) All-cause mortality RR, model 1 1.04 (0.91–1.18) 0.91 (0.82–1.01) 1.06 (0.88–1.28) 0.95 (0.78–1.17) RR, model 2 1.06 (0.86–1.31) 0.89 (0.80–0.99) 1.06 (0.86–1.31) 0.90 (0.73–1.12) RR, model 3 1.08 (0.91–1.28) 0.78 (0.65–0.94) 0.95 (0.71–1.26) 0.71 (0.51–1.00) RR, Relative risk with 95% confidence interval per standard deviation increase in urinary or dietary potassium, obtained by Cox proportional hazard analysis a 1 b c d e 5 2 Table 5 Relationship of urinary sodium/potassium ratio with cardiovascular events and all-cause mortality in Dutch men and women aged 55 years and over  a a Incident MI b 1.03 (0.93–1.14) 0.92 (0.76–1.13) c 1.02 (0.92–1.13) 0.90 (0.73–1.10) d 1.04 (0.93–1.17) 0.91 (0.72–1.16) Incident stroke RR, model 1 1.01 (0.89–1.13) 1.01 (0.83–1.23) RR, model 2 0.99 (0.86–1.13) 0.99 (0.77–1.20) RR, model 3 0.99 (0.83–1.18) 0.90 (0.66–1.22) CVD mortality e RR, model 1 0.88 (0.77–1.01) 0.85 (0.65–1.11) RR, model 2 0.93 (0.81–1.06) 0.86 (0.66–1.13) RR, model 3 0.92 (0.80–1.07) 0.91 (0.65–1.27) All-cause mortality RR, model 1 0.99 (0.91–1.06) 1.04 (0.91–1.18) RR, model 2 0.99 (0.92–1.08) 1.06 (0.93–1.22) RR, model 3 1.01 (0.91–1.12) 1.13 (0.93–1.36) RR, Relative risk with 95% confidence interval per 1 unit increase in urinary sodium/potassium ratio, obtained by Cox proportional hazard analysis a 1 b c d e Discussion In an unselected population of older Dutch subjects we found no consistent association of urinary sodium and potassium with CVD events or mortality. Dietary potassium estimated by food frequency questionnaire, however, was associated with a lower risk of all-cause mortality. Urinary sodium/potassium ratio was positively associated with mortality risk, but only in overweight subjects without CVD and hypertension at baseline. 29 30 31 16 11 12 6 7 15 16 19 21 11 32 33 34