Estimated net endogenous acid production and risk of prevalent and incident hypertension in community-dwelling older people

Table 1 Baseline characteristics and prevalent hypertension by quartiles of energy adjusted estimated net endogenous acid production (n = 3956)

Variable	Quartile of energy adjusted estimated NEAP (g/mEq)								Ptrend1
	Q1 (n = 987)		Q2 (n = 991)		Q3 (n = 989)		Q4 (n = 989)
	Mean	SD, %	Mean	SD, %	Mean	SD, %	Mean	SD, %
2Estimated NEAP (g/mEq)
Original	26.9	21.3, 32.7	41.2	37.0, 45.7	53.4	48.7, 58.2	71.2	64.5, 79.7	< 0.001
Energy adjusted	28.7	23.8, 32.7	41.8	39.0, 44.7	54.0	50.7, 57.3	71.2	65.7, 79.8	< 0.001
Age (yr)	72.3	4.9	72.4	5.3	72.5	5.2	72.7	5.4	0.055
BMI (kg/m2)	23.8	3.3	23.7	3.3	23.6	3.3	23.5	3.3	0.027
Male (%)		50.1		49.9		50.1		50.1	0.989
Education level (%)
Primary or below		77.7		72.4		67.2		68.8	< 0.001
Secondary/matriculation		16.8		19.0		19.8		19.4
University or above		5.5		8.7		12.9		11.8
Smoking habit (%)
Never smoke		58.5		62.6		65.4		66.5	< 0.001
Former smoker		33.0		31.1		29.3		26.1
Current smoker		8.5		6.4		5.3		7.4
Alcohol use (%)
Never		84.1		84.8		84.6		86.6	0.155
Former drinker		2.4		1.4		1.6		2.1
Current drinker		13.5		13.8		13.8		11.3
3Prevalent hypertension (%)		72.8		74.9		75.2		77.8	0.014
Energy intake (kcal/d)	1832.5	587.3	1847.5	555.1	1848.6	568.7	1821.6	561.2	0.696
2Energy adjusted fiber (g/d)	9.1	7.0, 11.7	8.9	6.8, 11.2	8.5	6.6, 10.5	7.5	5.7, 8.9	< 0.001
2Energy adjusted calcium (mg/d)	535.6	418.9, 692.4	573.6	452.3, 725.8	590.7	460.1, 763.1	547.5	418.8, 726.2	0.098
2Energy adjusted magnesium (mg/d)	358.5	297.9, 487.8	356.6	292.7, 471.5	344.4	291.2, 434.8	312.0	262.1, 373.2	< 0.001
2Energy adjusted potassium (mg/d)	3782.3	3180.4, 4507.6	2977.9	2536.0, 3437.3	2462.8	2092.3, 2935.4	2021.0	1677.8, 2440.5	< 0.001
2Energy adjusted sodium (mg/d)	1453.4	1036.9, 1963.4	1379.7	1040.7, 1886.0	1345.6	1030.3, 1793.3	1254.3	930.1, 1651.4	< 0.001
PASE score	93.2	43.6	92.5	42.4	91.2	43.0	88.4	42.9	0.011

¹P_trend was assessed by linear-by-linear association χ² test linear and ANOVA test for trend, or non-parametric Jonckheere-Terpstra test;

²Data are presented as median (interquartile range);

³Defined as average systolic or diastolic blood pressure ≥ 140 or 90 mmHg respectively, or use of anti-hypertensive medications. NEAP: Net endogenous acid production; PASE: The Physical Activity Scale of the Elderly; BMI: Body mass index; ANOVA: Analysis of variance.

Table 2 Spearman’s correlation between estimated net endogenous acid production and selected nutrients and main food groups (n = 3956)

Energy adjusted nutrients/	Energy adjusted estimated NEAP (g/mEq)
main food groups	rs	P
Total protein (g)	0.27	< 0.001
Vitamin C (mg)	-0.27	< 0.001
Calcium (mg)	0.04	0.015
Phosphorus (mg)	0.16	< 0.001
Fiber (g)	-0.23	< 0.001
Magnesium (mg)	-0.20	< 0.001
Vitamin K (mcg)	-0.17	< 0.001
Potassium (mg)	-0.68	< 0.001
Sodium (mg)	-0.10	< 0.001
Cereals (g)	-0.03	0.063
Egg and egg products (g)	0.03	0.034
Fish and shellfish (g)	0.07	< 0.001
Fruits and dried fruits (g)	-0.31	< 0.001
Legumes, seeds and nuts (g)	0.01	0.678
Meat and poultry (g)	0.13	< 0.001
Milk and milk products (g)	0.03	0.041
Vegetables (g)	-0.18	< 0.001

NEAP: Net endogenous acid production.

Table 3 Logistic regression linking to quartiles of energy adjusted estimated net endogenous acid production to prevalent hypertension (n = 3956)

	Quartiles of energy adjusted estimated NEAP (g/mEq)				Ptrend1
	Q1 (n = 987)	Q2 (n = 991)	Q3 (n = 989)	Q4 (n = 989)
No. of case and control	719/268	742/249	744/245	769/220
Unadjusted OR (95%CI)	1 (reference)	1.11 (0.91-1.36)	1.13 (0.93-1.38)	1.30 (1.06-1.60)	0.014
Age and sex adjusted OR (95%CI)	1 (reference)	1.11 (0.91-1.36)	1.13 (0.92-1.38)	1.29 (1.05-1.58)	0.020
2Multivariable adjusted OR (95%CI)	1 (reference)	1.22 (0.97-1.52)	1.35 (1.03-1.76)	1.66 (1.22-2.26)	0.002

¹P_trend by entering quartiles of energy adjusted NEAP as a fixed factor and testing the contrast by using the polynomial option in all models;

²Model adjusted for age, sex, BMI, PASE, education level, smoking status, alcohol use, and quartiles of energy adjusted intakes of fiber, calcium, magnesium, potassium and sodium. NEAP: Net endogenous acid production; BMI: Body mass index; PASE: The Physical Activity Scale of the Elderly.

Table 4 Logistic regression linking to quartiles of energy adjusted estimated net endogenous acid production to incident hypertension (n = 795)

	Quartiles of energy adjusted estimated NEAP (g/mEq)				Ptrend1
	Q1 (n = 198)	Q2 (n = 201)	Q3 (n = 198)	Q4 (n = 198)
No. of case and control	78/120	80/121	75/123	77/121
Unadjusted OR (95%CI)	1 (reference)	1.02 (0.68-1.52)	0.94 (0.63-1.41)	0.98 (0.65-1.47)	0.842
Age and sex adjusted OR (95%CI)	1 (reference)	1.03 (0.69-1.54)	0.95 (0.63-1.43)	0.99 (0.66-1.49)	0.873
2Multivariable adjusted OR (95%CI)	1 (reference)	1.15 (0.74-1.80)	1.11 (0.66-1.86)	1.32 (0.72-2.43)	0.436

¹P_trend by entering quartiles of energy adjusted NEAP as a fixed factor and testing the contrast by using the polynomial option in all models;

²Model adjusted for age, sex, BMI, PASE, education level, smoking status, alcohol use, and quartiles of energy adjusted intakes of fiber, calcium, magnesium, potassium and sodium. NEAP: Net endogenous acid production; BMI: Body mass index; PASE: The Physical Activity Scale of the Elderly.