Beijing

Guangzhou

Age group

Mean ± SD

n

Mean ± SD

n

20s

24.79 ± 2.29

90

26.14 ± 2.00

74

30s

35.52 ± 2.72

27

35.06 ± 3.16

49

40s

44.13 ± 3.09

62

44.45 ± 2.97

56

50s

55.20 ± 3.63

45

54.59 ± 4.01

37