Table 2.
Comparison of vitamin D status of pregnant women in CNHS 2010–2012 and CNHS 2015–2017 (%, 95% CI).
| Characteristics | Sufficiency (25(OH)D ≥ 20 ng/mL) | Insufficiency (20 ng/mL > 25(OH)D ≥ 12 ng/mL) | Deficiency (25(OH)D < 12 ng/mL) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 2010–2012 | 2015–2017 | p Value | 2010–2012 | 2015–2017 | p Value | 2010–2012 | 2015–2017 | p Value | |
| Total | 25.17 (23.27–27.08) | 12.57 (11.86–13.29) | <0.0001 | 49.30 (47.11–51.49) | 45.46 (44.39–46.54) | 0.002 | 25.52 (23.61–27.43) | 41.96 (40.9–43.03) | <0.0001 |
| City type | |||||||||
| Urban | 25.71 (23.03–28.38) | 12.43 (11.5–13.35) | <0.0001 | 48.30 (45.24–51.35) | 44.59 (43.2–45.98) | 0.031 | 26.00 (23.31–28.68) | 42.98 (41.6–44.37) | <0.0001 |
| Rural | 24.62 (21.92–27.32) | 12.79 (11.65–13.93) | <0.0001 | 50.36 (47.22–53.49) | 46.76 (45.06–48.47) | 0.048 | 25.03 (22.31–27.74) | 40.44 (38.77–42.12) a | <0.0001 |
| District | |||||||||
| Eastern | 32.60 (29.29–35.91) a | 19.21 (17.76–20.65) a | <0.0001 | 49.42 (45.89–52.95) | 46.36 (44.53–48.18) | 0.130 | 17.98 (15.27–20.69) c | 34.44 (32.7–36.18) b | <0.0001 |
| Central | 24.58 (21.42–27.74) b | 8.68 (7.59–9.77) b | <0.0001 | 51.82 (48.15–55.48) | 46.30 (44.37–48.24) | 0.009 | 23.60 (20.49–26.72) b | 45.01 (43.09–46.94) a | <0.0001 |
| Western | 14.89 (11.82–17.97) c | 9.30 (8.22–10.38) b | <0.001 | 45.65 (41.35–49.95) | 43.76 (41.92–45.61) | 0.428 | 39.46 (35.24–43.68) a | 46.94 (45.08–48.79) a | 0.002 |
| Location | |||||||||
| Northern | 17.72 (15.35–20.09) b | 4.49 (3.83–5.14) b | <0.0001 | 48.65 (45.55–51.75) | 37.50 (35.97–39.03) b | <0.0001 | 33.63 (30.7–36.57) a | 58.01 (56.46–59.57) a | <0.0001 |
| Southern | 32.57 (29.68–35.47) a | 19.75 (18.57–20.94) a | <0.0001 | 49.95 (46.86–53.04) | 52.53 (51.05–54.02) a | 0.140 | 17.48 (15.13–19.83) b | 27.72 (26.39–29.05) b | <0.0001 |
| Age group | |||||||||
| 18–24.9 y | 21.53 (18.65–24.41) a | 11.97 (10.57–13.37) | <0.0001 | 49.68 (46.18–53.18) | 45.40 (43.25–47.55) | 0.041 | 28.79 (25.62–31.96) | 42.63 (40.49–44.77) | <0.0001 |
| 25–29.9 y | 26.47 (23.41–29.54) a,b | 12.24 (11.21–13.27) | <0.0001 | 50.19 (46.71–53.66) | 45.41 (43.85–46.98) | 0.014 | 23.34 (20.4–26.28) | 42.35 (40.8–43.9) | <0.0001 |
| 30–34.9 y | 30.99 (25.86–36.12) b | 13.91 (12.22–15.6) | <0.0001 | 45.37 (39.85–50.89) | 45.22 (42.79–47.65) | 0.961 | 23.64 (18.93–28.35) | 40.87 (38.47–43.27) | <0.0001 |
| 35 y+ | 25.23 (17.14–33.31) a,b | 13.16 (10.55–15.77) | 0.003 | 51.35 (42.05–60.66) | 46.59 (42.75–50.44) | 0.689 | 23.42 (15.54–31.31) | 40.25 (36.47–44.03) | 0.010 |
| Latitude | |||||||||
| tropical | 59.84 (51.13–68.54) a | 41.42 (37.40–45.44) a | <0.001 | 36.89 (28.32–45.45) b | 41.59 (37.57–45.62) b | 0.407 | 3.28 (0.12–6.44) c | 16.98 (13.92–20.05) d | <0.0001 |
| subtropical | 28.55 (25.4–31.71) b | 17.70 (16.38–19.02) b | <0.0001 | 51.90 (48.41–55.4) a | 56.82 (55.11–58.54) a | 0.013 | 19.54 (16.77–22.31) b | 25.48 (23.97–26.99) c | <0.001 |
| warm temperate | 14.83 (12.34–17.33) c | 5.12 (4.36–5.89) c | <0.0001 | 48.72 (45.22–52.23) a,b | 35.85 (34.19–37.51) c | <0.0001 | 36.45 (33.07–39.82) a | 59.03 (57.32–60.73) a | <0.0001 |
| medium temperate | 28.98 (23.96–34) b | 5.01 (3.78–6.23) c | <0.0001 | 49.04 (43.51–54.58) a,b | 42.69 (39.91–45.47) b | 0.043 | 21.97 (17.39–26.56) b | 52.30 (49.49–55.1) b | <0.0001 |
| Nationality | |||||||||
| Han | 25.87 (23.85–27.89) a | 12.87 (12.09–13.64) a | <0.0001 | 49.64 (47.34–51.94) | 45.49 (44.34–46.64) | 0.002 | 24.49 (22.51–26.47) b | 41.64 (40.51–42.78) | <0.0001 |
| Ethnic minorities | 18.65 (13.15–24.15) b | 10.42 (8.5–12.33) b | 0.001 | 46.11 (39.08–53.15) | 45.25 (42.13–48.37) | 0.826 | 35.23 (28.49–41.98) a | 44.33 (41.22–47.44) | 0.020 |
| Gestational age | |||||||||
| First trimester | 26.62 (22.59–30.66) | 11.48 (10.19–12.77) | <0.0001 | 51.52 (46.95–56.08) | 45.96 (43.95–47.98) | 0.029 | 21.86 (18.09–25.63) | 42.56 (40.56–44.56) | <0.0001 |
| Second trimester | 26.29 (23.43–29.16) | 13.11 (11.98–14.24) | <0.0001 | 47.19 (43.95–50.44) | 45.56 (43.89–47.23) | 0.380 | 26.51 (23.64–29.38) | 41.33 (39.68–42.98) | <0.0001 |
| Third trimester | 22.52 (19.27–25.77) | 12.87 (11.54–14.2) | <0.0001 | 50.71 (46.82–54.6) | 44.84 (42.86–46.82) | 0.008 | 26.77 (23.32–30.22) | 42.29 (40.32–44.25) | <0.0001 |
| Pregnancy frequency | |||||||||
| 1 | 23.00 (20.70–25.31) a | 11.69 (10.66–12.72) a | <0.0001 | 49.69 (46.94–52.43) | 44.48 (42.88–46.07) | 0.001 | 27.31 (24.86–29.75) | 43.84 (42.24–45.43) a | <0.0001 |
| 2 | 28.57 (24.85–32.29) b | 12.46 (11.3–13.61) a | <0.0001 | 48.50 (44.38–52.62) | 46.28 (44.53–48.03) | 0.329 | 22.93 (19.46–26.39) | 41.26 (39.54–42.99) a,b | <0.0001 |
| 3+ | 30.43 (23.32–37.55) b | 15.34 (13.4–17.28) b | <0.0001 | 49.07 (41.34–56.8) | 46.32 (43.64–49) | 0.509 | 20.50 (14.26–26.74) | 38.35 (35.73–40.96) b | <0.0001 |
| BMI before pregnancy | |||||||||
| Thin | 43.88 (34.04–53.71) a | 18.69 (14.31–23.06) a | <0.001 | 42.86 (33.05–52.66) | 46.23 (40.63–51.83) | 0.373 | 13.27 (6.54–19.99) a | 35.08 (29.73–40.44) a | <0.0001 |
| Normal | 26.52 (23.69–29.34) b | 13.32 (12.24–14.39) b | <0.0001 | 47.39 (44.19–50.59) | 46.71 (45.13–48.29) | 0.950 | 26.09 (23.28–28.9) b | 39.97 (38.42–41.53) a | <0.0001 |
| Overweight | 21.50 (18.47–24.53) b | 11.63 (10.42–12.84) b | <0.0001 | 51.91 (48.22–55.6) | 44.24 (42.37–46.12) | <0.001 | 26.59 (23.33–29.85) b | 44.13 (42.25–46.01) b | <0.0001 |
| Obesity | 23.28 (18.16–28.4) b | 11.00 (9.34–12.65) b | <0.0001 | 51.53 (45.47–57.58) | 44.21 (41.58–46.84) | 0.029 | 25.19 (19.93–30.45) b | 44.79 (42.16–47.42) b | <0.0001 |
| Season | |||||||||
| Spring | / | 9.60 (7.67–11.53) c | / | 21.82 (10.89–32.74) b | 40.51 (37.3–43.73) b | 0.006 | 78.18 (67.26–89.11) a | 49.89 (46.61–53.16) a | <0.0001 |
| Summer | 36.00 (22.68–49.32) a | 30.00 (13.60–46.4) a | 0.584 | 50.00 (36.13–63.87) a | 66.67 (49.79–83.54) a | 0.150 | 14.00 (4.37–23.63) c | 3.33 (0–9.76) c | 0.128 |
| Autumn | 30.95 (28.02–33.87) a | 16.68 (14.99–18.37) b | <0.0001 | 49.64 (46.48–52.8) a | 55.62 (53.36–57.87) a | 0.003 | 19.42 (16.92–21.92) c | 27.70 (25.67–29.73) b | <0.0001 |
| Winter | 20.15 (17.58–22.72) b | 11.55 (10.69–12.40) b | <0.0001 | 50.53 (47.33–53.74) a | 42.65 (41.33–43.97) b | <0.0001 | 29.32 (26.4–32.23) b | 45.8 (44.47–47.13) a | <0.0001 |
| Vitamin D supplement intake | |||||||||
| No | 24.82 (22.82–26.82) | 11.74 (11.05–12.44) b | <0.0001 | 49.30 (46.99–51.62) | 43.24 (42.17–44.32) | 0.002 | 25.88 (23.85–27.91) | 40.54 (39.47–41.6) a | <0.0001 |
| Yes | 28.89 (22.26–35.52) | 18.53 (14.55–22.5) a | 0.006 | 51.67 (44.36–58.97) | 49.59 (44.47–54.71) | 0.649 | 19.44 (13.66–25.23) | 31.88 (27.11–36.65) b | 0.002 |
| unknown | 24.24 (9.61–38.88) | / | 36.36 (19.94–52.79) | / | 39.39 (22.71–56.08) | / | |||
| Education | |||||||||
| Primary | 29.66 (22.21–37.10) | 10.71 (8.09–13.34) | <0.0001 | 42.76 (34.70–50.82) | 42.48 (38.28–46.68) | 0.952 | 27.59 (20.31–34.87) | 46.80 (42.56–51.05) a | <0.0001 |
| Medium | 24.98 (22.55–27.41) | 12.99 (11.97–14) | <0.0001 | 50.94 (48.14–53.75) | 46.62 (45.12–48.12) | 0.008 | 24.08 (21.68–26.48) | 40.40 (38.92–41.87) b | <0.0001 |
| Advanced | 24.53 (21.19–27.87) | 12.35 (11.25–13.45) | <0.0001 | 47.66 (43.78–51.53) | 44.50 (42.83–46.16) | 0.140 | 27.81 (24.34–31.29) | 43.15 (41.49–44.81) a | <0.0001 |
| Marital status | |||||||||
| Married | 25.46 (23.53–27.38) a | 12.53 (11.81–13.25) | <0.0001 | 49.14 (46.93–51.35) | 45.41 (44.33–46.49) | 0.003 | 25.41 (23.48–27.33) | 42.06 (40.99–43.14) a | <0.0001 |
| Unmarried | 10.53 (0.76–20.29) b | 17.91 (8.73–27.09) | 0.314 | 57.89 (42.18–73.61) | 52.24 (40.28–64.20) | 0.577 | 31.58 (16.79–46.37) | 29.85 (18.89–40.81) b | 0.853 |
| Annual family income per capita | |||||||||
| Low | 22.86 (19.58–26.14) | 9.11 (7.76–10.47) b | <0.0001 | 50.79 (46.89–54.70) | 43.08 (40.75–45.41) b | <0.001 | 26.35 (22.91–29.79) | 47.81 (45.46–50.16) a | <0.0001 |
| Mid | 24.73 (21.63–27.83) | 11.45 (9.92–12.97) b | <0.0001 | 50.94 (47.35–54.54) | 42.81 (40.45–45.18) b | <0.001 | 24.33 (21.24–27.41) | 45.74 (43.35–48.12) a | <0.0001 |
| High | 28.57 (24.45–32.69) | 14.39 (12.81–15.97) a | <0.0001 | 45.24 (40.70–49.78) | 48.89 (46.63–51.14) a | 0.159 | 26.19 (22.18–30.20) | 36.72 (34.55–38.89) b | <0.0001 |
| NR | 26.47 (19.83–33.11) | 14.11 (12.84–15.38) a | <0.0001 | 47.65 (40.13–55.16) | 46.19 (44.37–48.00) a,b | 0.711 | 25.88 (19.29–32.47) | 39.70 (37.92–41.48) b | <0.001 |
a,b,c refers to statistical difference in subgroups, p < 0.05.