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

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.