Table 2 The association between SP frequency and frailty based on fixed-effects model and time-varying Cox regression

Frequency of SP (ref. Non SP)

  Occasional

0.000 (-0.003, 0.002)

0.776

0.93 (0.83, 1.04)

  Weekly

-0.006 (-0.009, -0.003)

 < 0.001

0.97 (0.86, 1.09)

  Daily

-0.009 (-0.012, -0.007)

 < 0.001

0.76 (0.69, 0.84)

Age

0.002 (0.001, 0.002)

 < 0.001

1.01 (1.00, 1.01)

Gender (ref. Male)

  Female

0.019 (-0.043, 0.080)

0.554

1.87 (1.67, 2.10)

Rural/urban residence (ref. Rural)

  Urban^a

–

–

0.75 (0.68, 0.82)

Education level (ref. Less than lower secondary)

  Upper secondary & vocational training

-0.014 (-0.025, -0.003)

0.015

0.73 (0.64, 0.84)

  Tertiary

-0.025 (-0.046, -0.004)

0.020

0.62 (0.42, 0.90)

Marital status (ref. Divorced or widowed)

  Married

-0.027 (-0.032, -0.021)

 < 0.001

0.77 (0.68, 0.86)

Hukou status (ref. Agricultural)

  Non-agricultural

-0.010 (-0.016, -0.004)

0.002

0.74 (0.66, 0.84)

  Other

-0.010 (-0.019, 0.000)

0.044

0.81 (0.56, 1.18)

Public health insurance coverage (ref. Not covered)

  Covered

0.002 (-0.002, 0.006)

0.441

0.83 (0.69, 1.00)

Current work status (ref. Not working)

  Working

-0.018 (-0.020, -0.015)

 < 0.001

0.94 (0.86, 1.03)

Comorbidity (ref. None)

  Single

0.030 (0.026, 0.034)

 < 0.001

2.10 (1.83, 2.41)

  Morbidity

0.072 (0.067, 0.076)

 < 0.001

5.03 (4.43, 5.70)

Household per capita consumption group (ref. low)

  Low to middle

0.000 (-0.003, 0.002)

0.890

0.91 (0.81, 1.02)

  Middle

0.008 (0.005, 0.010)

 < 0.001

0.93 (0.84, 1.04)

  High

0.014 (0.011, 0.016)

 < 0.001

0.97 (0.87, 1.09)

Alcohol intake (ref. Do not drink)

  Drink

-0.001 (-0.004, 0.002)

0.407

0.96 (0.88, 1.06)

Smoking status (ref. Never)

  Quit now

0.011 (0.006, 0.016)

 < 0.001

1.20 (1.05, 1.38)

  Smoke now

0.000 (-0.005, 0.005)

0.973

1.25 (1.11, 1.40)