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Table 1 Characteristics of the study participants according to cooking fuel used at the baseline

From: Association between biomass fuel use and the risk of cognitive impairment among older populations in China: a population-based cohort study

Characteristics N Cooking fuel χ2 P
Clean fuel Never cooked in the home Biomass fuel others
Total 4145 2228 (53.75) 59 (1.42) 1676 (40.43) 182 (4.39)   
Demographic characteristics
 Age (years)       56.798a < 0.0001
  65–84 2460 1308 (53.17) 10 (0.41) 1042 (42.36) 100 (4.07)   
  85–104 1606 873 (54.36) 45 (2.80) 611 (38.04) 77 (4.79)   
   ≥ 105 79 47 (59.49) 4 (5.06) 23 (29.11) 5 (6.33)   
 Sex       10.97 0.012
  Male 2123 1128 (53.13) 30 (1.41) 891 (41.97) 74 (3.49)   
  Female 2022 1100 (54.40) 29 (1.43) 785 (38.82) 108 (5.34)   
 Education       69.409 < 0.0001
  No school 2103 998 (47.46) 39 (1.85) 960 (45.65) 106 (5.04)   
  1 year or more 2040 1228 (60.20) 20 (0.98) 716 (35.10) 76 (3.73)   
 Residence       325.472 < 0.0001
  Urban 1815 1249 (68.82) 26 (1.43) 455 (25.07) 85 (4.68)   
  Rural 2330 979 (42.02) 33 (1.42) 1221 (52.40) 97 (4.16)   
 Household income CNY       486.859a < 0.0001
   < 10,000 1565 544 (34.76) 42 (2.68) 910 (58.15) 69 (4.41)   
  10,001–30,000 1032 568 (55.04) 3 (0.29) 414 (40.12) 47 (4.55)   
   > 30,000 1548 1116 (72.09) 14 (0.90) 352 (22.74) 66 (4.26)   
 Marital status       83.076a < 0.0001
  Unmarried 34 13 (38.24) 0 (0.00) 19 (55.88) 2 (5.88)   
  Married 1952 1020 (52.25) 1 (0.05) 856 (43.85) 75 (3.84)   
  Divorced or widowed 2107 1168 (55.43) 57 (2.71) 781 (37.07) 101 (4.79)   
Lifestyle habits
 Smoking status       3.412 0.332
  Non-smoker 2781 1502 (54.01) 35 (1.26) 1114 (40.06) 130 (4.67)   
  Smoker 1348 717 (53.19) 23 (1.71) 557 (41.32) 51 (3.78)   
 Drinking status       4.065 0.255
  Non-drinker 2974 1589 (53.43) 48 (1.61) 1199 (40.32) 138 (4.64)   
  Drinker 1138 623 (54.75) 11 (0.97) 461 (40.51) 43 (3.78)   
 Regular exercise       253.79 < 0.0001
  Yes 1383 975 (70.50) 8 (0.58) 328 (23.72) 72 (5.21)   
  No 2668 1204 (45.13) 50 (1.87) 1309 (49.06) 105 (3.94)   
 Ventilation of the kitchen when cooking at home       536.392a < 0.0001
  No ventilation 273 83 (30.40) 3 (1.10) 172 (63.00) 15 (5.49)   
  Kitchen ventilation or fan 1061 845 (79.64) 9 (0.85) 182 (17.15) 25 (2.36)   
  By opening window 1554 609 (39.19) 13 (0.84) 854 (54.95) 78 (5.02)   
  Unknown 1257 691 (54.97) 34 (2.70) 468 (37.23) 64 (5.09)   
 Fresh fruit       49.406 < 0.0001
  Almost or quite often 1779 1060 (59.58) 30 (1.69) 626 (35.19) 63 (3.54)   
  Occasionally 1413 711 (50.32) 13 (0.92) 620 (43.88) 69 (4.88)   
  Rarely or never 943 455 (48.25) 15 (1.59) 424 (44.96) 49 (5.20)   
 Vegetables       66.510a 0.001
  Almost or quite often 3758 2052 (54.60) 52 (1.38) 1497 (39.84) 157 (4.18)   
  Occasionally 289 126 (43.60) 3 (1.04) 144 (49.83) 16 (5.54)   
  Rarely or never 90 48 (53.33) 3 (3.33) 31 (34.44) 8 (8.89)   
Health status
 Limited in activities because of health problems during the last six months       21.041 < 0.0001
  Yes 3099 1637 (52.82) 33 (1.06) 1300 (41.95) 129 (4.16)   
  No 1041 586 (56.29) 26 (2.50) 376 (36.12) 53 (5.09)   
 Body mass index (kg/m2)       74.429a < 0.0001
  Underweight (<  18.5) 636 310 (48.74) 14 (2.20) 276 (43.40) 36 (5.66)   
  Normal (18.5–23.9) 2242 1178 (52.54) 20 (0.89) 946 (42.19) 98 (4.37)   
  Overweight (24–27.9) 840 493 (58.69) 11 (1.31) 308 (36.67) 28 (3.33)   
  Obese (≥28) 263 165 (62.74) 4 (1.52) 75 (28.52) 19 (7.22)   
  Unknown 164 82 (50.00) 10 (6.10) 71 (43.29) 1 (0.61)   
 Hypertension       37.117 < 0.0001
  Yes 1413 838 (59.31) 17 (1.20) 486 (34.39) 72 (5.10)   
  No 2532 1283 (50.67) 37 (1.46) 1109 (43.80) 103 (4.07)   
  Unknown 200 107 (53.50) 5 (2.50) 81 (40.50) 7 (3.50)   
 Diabetes       26.406a < 0.0001
  Yes 243 163 (67.08) 1 (0.41) 65 (26.75) 14 (5.76)   
  No 3661 1939 (52.96) 55 (1.50) 1514 (41.35) 153 (4.18)   
  Unknown 241 126 (52.28) 3 (1.24) 97 (40.25) 15 (6.22)   
 Heart diseases      38.774a < 0.0001
  Yes 524 336 (64.12) 6 (1.15) 152 (29.01) 30 (5.73)   
  No 3390 1772 (52.27) 49 (1.45) 1432 (42.24) 137 (4.04)   
  Unknown 231 120 (51.95) 4 (1.73) 92 (39.83) 15 (6.49)   
 Stroke       24.390a < 0.001
  Yes 313 195 (62.30) 2 (0.64) 92 (29.39) 24 (7.67)   
  No 3604 1912 (53.05) 54 (1.50) 1491 (41.37) 147 (4.08)   
  Unknown 228 121 (53.07) 3 (1.32) 93 (40.79) 11 (4.82)   
  1. Notes: a: Fisher exact test; missing data: education 2 (0.05%), marital status 47 (1.25%), smoking status 16 (0.39%), drinking status 33 (0.80%), regular exercise 94 (2.27%), diet of fresh fruit 10 (0.24%) and vegetables 8 (0.12%), and limited in activities because of health problems during the last six months 5 (0.12%)