Serum bicarbonate concentration and the risk of cardiovascular disease and death in type 2 diabetes: the Fremantle Diabetes Study

Table 3 Hazard ratio (95 % CI) of serum bicarbonate concentration as quintiles and as a continuous variable for all-cause mortality, incident coronary heart disease and incident heart failure in patients with type 2 diabetes unadjusted or adjusted for the respective most parsimonious Cox proportional hazards models

	Serum bicarbonate quintile (mmol/L)
	Q1 ≤23	Q2 24–25	Q3 26–27	Q4 28	Q5 ≥29	All increase of 1
All-cause mortality
Number	183	219	341	178	362	1283^a
Number of events (%)	104 (56.8)	122 (55.7)	182 (53.4)	97 (54.5)	227 (62.7)	732 (57.1)
Unadjusted	1.27 (1.004–1.60)	1.07 (0.86–1.33)	1.02 (0.84–1.24)	1.01 (0.80–1.29)	1.00 (reference)	0.98 (0.96–1.004)
Adjusted^b	1.25 (0.96–1.63)	1.07 (0.83–1.38)	1.04 (0.83–1.29)	1.10 (0.84–1.43)	1.00 (reference)	0.98 (0.95–1.004)
Coronary heart disease
Number	135	154	248	138	230	905^c
Number of events (%)	59 (43.7)	70 (45.5)	93 (37.5)	50 (36.2)	89 (38.7)	361 (39.9)
Unadjusted	1.58 (1.14–2.20)	1.53 (1.12–2.10)	1.14 (0.86–1.53)	0.97 (0.68–1.37)	1.00 (reference)	0.94 (0.91–0.97)
Adjusted^d	1.39 (0.97–1.98)	1.23 (0.88–1.72)	0.97 (0.71–1.31)	0.92 (0.64–1.32)	1.00 (reference)	0.95 (0.92–0.99)
Heart failure
Number	172	200	325	167	310	1174^e
Number of events (%)	66 (38.4)	58 (29.0)	98 (30.2)	44 (26.3)	108 (34.8)	374 (31.9)
Unadjusted	1.54 (1.13–2.09)	1.04 (0.76–1.43)	1.05 (0.80–1.38)	0.81 (0.57–1.15)	1.00 (reference)	0.95 (0.92–0.98)
Adjusted^f	1.08 (0.76–1.53)	0.82 (0.58–1.16)	0.90 (0.67–1.21)	0.77 (0.52–1.13)	1.00 (reference)	0.99 (0.95–1.03)

^a13 participants had missing serum bicarbonate
^bAdjusted for age as time scale, age at baseline, sex, Aboriginal, current smoking status, any exercise in the past 2 weeks, ACE-inhibitor use, diuretic use, diabetes duration, on lipid-modifying medication, log_e(urinary albumin:creatinine ratio), retinopathy, peripheral sensory neuropathy, peripheral arterial disease, coronary heart disease, comorbidities (Charlson Comorbidity Index excluding diabetes and its complications)
^c383 had a history of CHD at baseline, 8 had missing serum bicarbonate
^dAdjusted for age as time scale, age at baseline, sex, not fluent in English, diabetes duration, log_e(serum triglycerides), log_e(urinary albumin:creatinine ratio), peripheral sensory neuropathy, peripheral arterial disease
^e111 had a history of HF at baseline, 11 had missing serum bicarbonate
^fAdjusted for age as time scale, age at baseline, currently married/de facto relationship, any exercise in the past 2 weeks, on digoxin, log_e(urinary albumin:creatinine ratio), eGFR (CKD-EPI) ≥90 or <30 mL/min/1.73 m², retinopathy, peripheral sensory neuropathy, coronary heart disease, cerebrovascular disease, schizophrenia

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