Table 2. Incidence rate and hazard ratios of dementia in different severity and visiting numbers of hyponatremia.
| Outcome | Event | Person–Years | Rate | Crude HR (95% CI) | Adjusted HR (95% CI) # |
|---|---|---|---|---|---|
| Dementia (ICD-9-CM 290, 294.1 and 331.0) | |||||
| Comparison cohort | 1056 | 100778 | 10.5 | 1.00 | 1.00 |
| Hyponatremia cohort | 424 | 15081 | 28.1 | 2.61(2.33 to 2.93)*** | 2.36(2.09 to 2.66)*** |
| Non-severe hypernatremia | 324 | 13843 | 23.4 | 2.19(1.93 to 2.48)*** | 2.08(1.83 to 2.37)*** |
| Severe hypernatremia | 100 | 1238 | 80.8 | 7.32(5.96 to 9.00)*** | 4.29(3.47 to 5.31)*** |
| Hyponatremia visiting numbers, per year | |||||
| ≤ 2 | 248 | 14465 | 17.2 | 1.64(1.49 to 1.79)*** | 1.54(1.33 to 1.77)*** |
| > 2 | 176 | 616 | 285.7 | 27.3(24.6 to 30.3)*** | 15.7(13.1 to 19.0)*** |
| p-value for trend | < 0.0001 | < 0.0001 | |||
| Alzheimer disease (ICD-9-CM 331.0) | |||||
| Comparison cohort | 61 | 100778 | 0.61 | 1.00 | 1.00 |
| Hyponatremia cohort | 19 | 15081 | 1.26 | 2.13(1.27 to 3.57)** | 2.31(1.35 to 3.95)** |
| Non-severe hypernatremia | 17 | 13843 | 1.23 | 2.07(1.21 to 3.55)** | 2.35(1.34 to 4.10)** |
| Severe hypernatremia | 2 | 1238 | 1.62 | 2.81(0.69 to 11.5) | 2.04(0.49 to 8.53) |
| Non-Alzheimer dementia (ICD-9-CM 290, and 294.1) | |||||
| Comparison cohort | 995 | 100778 | 9.87 | 1.00 | 1.00 |
| Hyponatremia cohort | 405 | 15081 | 26.9 | 2.64(2.35 to 2.97)*** | 2.36(2.09 to 2.66)*** |
| Non-severe hypernatremia | 307 | 13843 | 22.2 | 2.19(1.93 to 2.49)*** | 2.07(1.81 to 2.36)*** |
| Severe hypernatremia | 98 | 1238 | 79.2 | 7.57(6.15 to 9.33)*** | 4.38(3.53 to 5.43)*** |
Medical visit, including outpatient and inpatient visits. PY, person–year; Rate, incidence rate (per 1,000 person–years); IRR, incidence rate ratio; #Adjusted for age, gender, comorbidity, and medicine used
** p < 0.01
*** p < 0.001.