Table 2.

The risk for incident dementia associated with 25(OH)D by seasons

	25(OH)D
	Normal	Insufficient	Deficient	p-trend
Spring
Range (nmol/L)	10.0–17.8	17.9–35.2	≥35.3
Events	281	186	33
Person-years	319,338	146,930	24,354
Incidence	0.9	1.3	1.4
HR (95% CI), Model 1	1.0	1.5 (1.2–1.8)	1.6 (1.1–2.3)	<0.0001
HR (95% CI), Model 2	1.0	1.5 (1.3–1.8)	1.6 (1.1–2.3)	<0.0001
Summer
Range (nmol/L)	10.0–28.0	28.1–50.4	≥50.5
Events	314	179	55
Person-years	302,662	137,969	22,775
Incidence	1.0	1.3	2.41
HR (95% CI), Model 1	1.0	1.3 (1.1–1.6)	2.5 (1.9–3.3)	<0.0001
HR (95% CI), Model 2	1.0	1.3 (1.1–1.5)	1.9 (1.4–2.6)	<0.0001
Autumn
Range (nmol/L)	10.0–24.0	24.1–46.2	≥46.3
Events	263	140	52
Person-years	272,827	125,247	20,621
Incidence	1.0	1.1	2.5
HR (95% CI), Model 1	1.0	1.2 (1.0–1.5)	2.7 (2.0–3.7)	<0.0001
HR (95% CI), Model 2	1.0	1.1 (0.9–1.4)	2.1 (1.5–2.9)	<0.0001
Winter
Range (nmol/L)	10.0–16.9	17.0–33.4	≥33.5
Events	217	122	32
Person-years	227,625	10,4421	17,049
Incidence	1.0	1.2	1.9
HR (95% CI), Model 1	1.0	1.3 (1.0–1.6)	2.1 (1.4–3.0)	0.0002
HR (95% CI), Model 2	1.0	1.2 (0.9–1.5)	1.7 (1.1–2.5)	0.0246
Combined
Events	1,075	627	172
Person-years	1,122,451	514,566	84,800
Incidence	1.0	1.2	2.0
HR (95% CI), Model 1	1.0	1.3 (1.2–1.5)	2.2 (1.9–2.6)	<0.0001
HR (95% CI), Model 2	1.0	1.3 (1.1–1.4)	1.8 (1.6–2.2)	<0.0001

Incidence of dementia represents number of cases per 1000 person-years. Hazard ratio (95% CI) for incident dementia associated with 25(OH)D status was estimated using Cox proportional regression models. Model 1 was adjusted for age and gender; Model 2 was adjusted for model 1 plus the day of the year when serum was collected, ethnicity, education, income, diet score, 25(OH)D supplement, smoking, alcohol consumption, sleep, physical activity, BMI, cholesterol, glycosylated hemoglobin, cystatin C, depression, hypertension, diabetes, heart disease, and chronic kidney disease at baseline.