Table 2. Participant characteristics.

Characteristic	Normonatremic participants	Hyponatremic participants	P value
Number (N)	94	33
Age (years)
Mean (± SD)	78 (±8)	81 (±7)	0.083
Range	65–97	69–98
Female sex, % (N)	76.6 (72)	81.8 (27)	0.078
Previous residence, % (N)
Own home	85.1 (80)	78.8 (26)	0.390
Sheltered housing	14.9 (14)	12.1 (4)
Care home	0	6.1 (2)
Care of the elderly ward	0	3.0 (1)
Number of co-morbidities
Mean (± SD)	4 (±2)	5 (±3)	0.222
Range	0–9	0–11
Number of co-morbidities that cause hyponatremia (N)
Mean (± SD)	1 (±1)	1 (±1)	0.855
Range	0–3	0–4
% of participants with at least one co-morbidity that causes hyponatremia (N)	60.6 (57)	54.5 (18)	0.681
Number of medications (N)
Mean (± SD)	5 (±4)	6 (±3)	0.294
Range	0–15	0–15
% of participants on at least one medication that causes hyponatremia (N)	64.9 (61)	72.7 (24)	0.52
Fracture site, % (N)			0.115
Hip	50.0 (47)	57.6 (19)
Hip and upper limb	1.1 (1)	0
Other lower limb	24.5 (23)	15.2 (5)
Other lower limb and upper limb	0	3.0 (1)
Upper limb	21.3 (20)	15.2 (5)
Pelvic	3.3 (3)	3.0 (1)
Vertebrae	0	6.1 (2)
Time from fracture to hospital admission (days)
Median	0	0	0.581
Interquartile range	0–1	0–1.5
Serum sodium prior to admission (mMol/L)
Mean (± SD)	140 (±2)	136 (±5)	<0.001
Range	133–145	127–144
Serum sodium on admission (mMol/L)
Mean (± SD)	139 (±2)	134 (±4)	<0.001
Range	135–146	127–144
Prevalence of hyponatremia, % (N)
Prior to admission*	3.2 (3)	30.3 (10)	<0.001
On admission	0	51.5 (17)	<0.001

*According to last serum sodium available prior to admission.