Age-dependent changes in the association between sleep duration and impaired glucose metabolism

Table 1 Characteristics of younger subjects classified by sleep duration

Sleep duration	≤ 5 h	6 h	7 h	≥ 8 h	P values
n (%)	4110 (12.5)	16265 (49.4)	9377 (28.5)	3177 (9.6)
Male, n (%)	2865 (69.7)	11121 (68.4)	6349 (67.7)	2026 (63.8)	< 0.0001
Age (yr)	30.5 ± 5.5	30.4 ± 5.3	30.7 ± 5.3	31.1 ± 5.3	< 0.0001
BMI (kg/m2)	23.4 ± 3.9	23.1 ± 3.7	22.8 ± 3.6	23.0 ± 3.8	< 0.0001
Systolic blood pressure (mmHg)	118 ± 14.3	118 ± 14.5	118 ± 14.6	119 ± 14.8	0.58
White blood cell count (× 109/L)	6.67 ± 1.8	6.48 ± 1.7	6.46 ± 1.7	6.48 ± 1.9	< 0.0001
Serum triglycerides (mmol/L)	0.9 (0.6-1.5)	0.9 (0.6-1.4)	0.9 (0.6-1.5)	0.9 (0.6-1.5)	0.46
Serum HDL-cholesterol (mmol/L)	1.6 ± 0.4	1.6 ± 0.4	1.6 ± 0.4	1.6 ± 0.4	0.04
HbA1c (NGSP, %)	5.35 ± 0.5	5.32 ± 0.5	5.30 ± 0.4	5.29 ± 0.5	< 0.0001
Work duration (h/d)	9.4 ± 1.5	9.0 ± 1.4	8.6 ± 1.3	8.1 ± 1.4	< 0.0001
Pharmacotherapy for
Hypertension, n (%)	25 (0.6)	73 (0.4)	38 (0.4)	19 (0.6)	0.29
Diabetes, n (%)	13 (0.3)	39 (0.2)	22 (0.2)	11 (0.3)	0.83
Dyslipidemia, n (%)	11 (0.3)	46 (0.3)	24 (0.3)	22 (0.7)	0.0001
Current smokers, n (%)	1791 (43.6)	5980 (36.8)	3221 (34.4)	964 (30.3)	< 0.0001
Everyday alcohol consumers, n (%)	353 (8.6)	1386 (8.5)	1022 (10.9)	370 (11.6)	< 0.0001
Regular exercisers, n (%)1	553 (14.4)	3154 (17.2)	2740 (19.4)	1367 (21.8)	< 0.0001
Past history of
CVD, n (%)	46 (1.1)	129 (0.8)	102 (1.1)	46 (1.4)	0.002

Data are presented as mean ± SD, median (interquartile range), or n (%). P values were determined by ANOVA and χ² tests were used for continuous and categorical variables. Serum triglyceride concentrations were log transformed before parametric analysis.

¹Regular exercise was defined as ≥ 30 min exercise per session at least twice a week. Values of white blood cell count are only available in 32713 subjects (n = 4073, 16171, 9313, and 3156, for ≤ 5 h, 6 h, 7 h, and ≥ 8 h sleep duration, respectively). BMI: Body mass index; HDL: High-density lipoprotein; NGSP: National Glycohemoglobin Standardization Program; CVD: Cardiovascular disease.

Table 2 Characteristics of older subjects classified by sleep duration

Sleep duration	≤ 5 h	6 h	7 h	≥ 8 h
n (%)	3838 (9.0)	18319 (43.1)	14115 (33.2)	6271 (14.7)
Male, n (%)	2197 (57.2)	11630 (63.5)	10399 (73.7)	5108 (81.5)
Age (yr)	49.4 ± 6.9	50.4 ± 6.8	51.8 ± 7.2	54.3 ± 8.4
BMI (kg/m²)	23.9 ± 3.7	23.8 ± 3.5	23.7 ± 3.3	23.7 ± 3.2
Systolic blood pressure (mmHg)	125 ± 18.2	126 ± 18.2	128 ± 18.4	131 ± 19.0
White blood cell count (× 109/L)	6.6 ± 1.8	6.5 ± 1.7	6.5 ± 1.7	6.6 ± 1.8
Serum triglycerides (mmol/L)	1.1 (0.7-1.8)	1.2 (0.8-1.8)	1.3 (0.8-1.9)	1.3 (0.9-2.0)
Serum HDL-cholesterol (mmol/L)	1.6 ± 0.4	1.6 ± 0.4	1.6 ± 0.4	1.6 ± 0.4
HbA1c (NGSP, %)	5.69 ± 0.8	5.69 ± 0.8	5.70 ± 0.8	5.77 ± 0.9
Work duration (h/d)	8.9 ± 1.7	8.5 ± 1.5	8.3 ± 1.3	8.1 ± 1.3
Pharmacotherapy for
Hypertension, n (%)	355 (9.3)	1970 (10.8)	1843 (13.1)	1091 (17.4)
Diabetes, n (%)	138 (3.6)	633 (3.5)	559 (4.0)	343 (5.5)
Dyslipidemia, n (%)	109 (2.8)	621 (3.4)	536 (3.8)	278 (4.4)
Current smokers, n (%)	1239 (32.3)	5981 (32.6)	4982 (35.3)	2580 (41.1)
Everyday alcohol consumers, n (%)	651 (17.0)	3378 (18.4)	3493 (24.7)	2009 (32.0)
Regular exercisers, n (%)1	611 (14.9)	2938 (18.1)	1913 (20.4)	617 (19.4)
Past history of
CVD, n (%)	125 (3.3)	620 (3.4)	568 (4.0)	323 (5.2)

Data are presented as mean ± SD, median (interquartile range), or n (%). P values determined by ANOVA and χ² tests for all continuous and categorical variables listed above were < 0.0001 (data not shown). Serum triglyceride concentrations were log transformed before parametric analysis.

¹Regular exercise was defined as ≥ 30 min exercise per session at least twice a week. Values of white blood cell count are only available in 42124 subjects (n = 3809, 18172, 13973, and 6170, for ≤ 5 h, 6 h, 7 h, and ≥ 8 h sleep duration, respectively). BMI: Body mass index; HDL: High-density lipoprotein; NGSP: National Glycohemoglobin Standardization Program; CVD: Cardiovascular disease.

Table 3 Odds ratios (95%CIs) of sleep duration for prediabetes and diabetes in younger subjects n (%)

Sleep durations	≤ 5 h	6 h	7 h	≥ 8 h	P value
Prediabetes
Cases	418 (10.2)	1463 (9.0)	743 (7.9)	229 (7.2)
Model 1	1.32 (1.16-1.49)d	1.15 (1.05-1.26)b	1 (reference)	0.90 (0.77-1.05)	0.88 (0.84-0.92)d
Model 2	1.32 (1.16-1.50)d	1.18 (1.07-1.29)b	1 (reference)	0.89 (0.76-1.04)	0.87 (0.83-0.91)d
Model 3	1.20 (1.05-1.37)b	1.12 (1.02-1.24)a	1 (reference)	0.84 (0.72-0.99)a	0.90 (0.86-0.95)d
Diabetes
Cases	58 (1.4)	150 (0.9)	77 (0.8)	27 (0.9)
Model 1	1.73 (1.23-2.44)b	1.12 (0.85-1.42)	1 (reference)	1.04 (0.67-1.61)	0.83 (0.72-0.96)a
Model 2	1.72 (1.22-2.43)b	1.16 (0.88-1.52)	1 (reference)	1.01 (0.65-1.58)	0.83 (0.72-0.95)b
Model 3	1.35 (0.93-1.97)	1.02 (0.76-1.37)	1 (reference)	0.92 (0.58-1.46)	0.90 (0.78-1.04)

Model 1: Unadjusted; Model 2: Adjusted for age and sex; Model 3: Model 2 plus adjustment for current smoking (vs non-smoking), daily alcohol consumption (vs infrequent/no alcohol consumption), regular exercise (vs no regular exercise), pharmacotherapy (hypertension, diabetes, and dyslipidemia), BMI, WBC count, systolic blood pressure, triglycerides, HDL-cholesterol, duration of work (as continuous variables), and past history of CVD (vs no history). Triglyceride concentrations were log transformed before analysis. Regular exercise was defined as ≥ 30 min exercise per session at least twice a week.

^aP < 0.05,

^bP < 0.01,

^dP < 0.001. BMI: Body mass index; HDL: High-density lipoprotein; CVD: Cardiovascular disease; WBC: White blood cell.

Table 4 Odds ratios (95%CIs) of sleep duration for prediabetes and diabetes in older subjects n (%)

Sleep duration	≤ 5 h	6 h	7 h	≥ 8 h	P value
Prediabetes
Cases	1259 (32.8)	6006 (32.8)	4788 (33.9)	2343 (37.4)
Model 1	0.95 (0.88-1.03)	0.95 (0.91-0.995)a	1 (reference)	1.16 (1.09-1.24)d	1.07 (1.05-1.10)d
Model 2	1.17 (1.09-1.27)d	1.08 (1.03-1.14)b	1 (reference)	0.97 (0.91-1.03)	0.94 (0.91-0.96)d
Model 3	1.12 (1.03-1.21)b	1.04 (0.99-1.11)	1 (reference)	0.97 (0.91-1.04)	0.96 (0.94-0.99)b
Diabetes
Cases	271 (7.1)	1379 (7.5)	1181 (8.4)	702 (11.2)
Model 1	0.83 (0.73-0.95)b	0.89 (0.82-0.97)b	1 (reference)	1.38 (1.25-1.52)d	1.19 (1.15-1.24)d
Model 2	1.10 (0.95-1.26)	1.06 (0.98-1.15)	1 (reference)	1.11 (1.00-1.22)	1.00 (0.96-1.04)
Model 3	1.02 (0.88-1.18)	1.01 (0.93-1.11)	1 (reference)	1.11 (1.02-1.25)a	1.03 (0.99-1.08)

Model 1: Unadjusted; Model 2: Adjusted for age and sex; Model 3: Model 2 plus adjustment for current smoking (vs non-smoking), daily alcohol consumption (vs infrequent/no alcohol consumption), regular exercise (vs no regular exercise), pharmacotherapy (hypertension, diabetes and dyslipidemia), BMI, WBC count, systolic blood pressure, triglycerides, HDL-cholesterol, duration of work (as continuous variables), and past history of CVD (vs no history). Triglyceride concentrations were log transformed before analysis. Regular exercise was defined as ≥ 30 min exercise per session at least twice a week.

^aP < 0.05,

^bP < 0.01,

^dP < 0.001. BMI: Body mass index; HDL: High-density lipoprotein; CVD: Cardiovascular disease; WBC: White blood cell.