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Table 2 Proportions of person-time and crude incidence rates of intestinal infectious diseases, 1995 to 2003 inclusive, stratified by categories of each socio-demographic, temporal, and environmental variable.

From: Water and sewage systems, socio-demographics, and duration of residence associated with endemic intestinal infectious diseases: A cohort study

Variable & Category

Proportion of person-time in each category

Crude rate of physician visitsa per 100,000 person-years

[95% CI]

Crude rate of hospitalizationsb per 100,000 person-years

[95% CI]

Sex

   Female

50.4%

1,398 [1351, 1442]

35.8 [28.6, 43.0]

   Male

49.6%

1,310 [1265, 1354]

31.8 [24.9, 38.5]

Age

   < 1

0.3%

7,848 [6484, 9175]

119 [0, 284]

   1 - 4

5.0%

6,607 [6286, 6928]

315 [ 249, 381]

   5 - 9

7.4%

2,164 [2014, 2314]

55.8 [33.0, 78.5]

   10 - 19

16.2%

902 [838, 967]

21.9 [12.0, 31.6]

   20 - 29

11.5%

1,548 [1448, 1648]

11.3 [3.0, 19.9]

   30 - 39

15.2%

1,190 [1114, 1266]

6.2 [0.8, 11.6]

   40 - 49

17.5%

770 [713, 827]

8.8 [2.7, 14.6]

   50 - 59

12.2%

653 [591, 716]

7.7 [1.0, 14.7]

   60 - 69

7.2%

756 [667, 843]

24.1 [8.3, 39.8]

   ≥ 70

7.5%

1,095 [991, 1196]

38.3 [19.0, 57.8]

Season

   Spring

25.5%

1,566 [1496, 1631]

56.2 [43.5, 68.7]

   Summer

25.6%

1,288 [1229, 1351]

21.2 [13.5, 29.0]

   Fall

25.2%

1,128 [1070, 1186]

19.3 [11.9, 26.7]

   Winter

23.7%

1,438 [1369, 1503]

38.7 [27.9, 49.7]

Duration of Residence in the Township

   < 1 year

15.0%

2,325 [2219, 2433]

65.7 [47.8, 83.5]

   1 - 2 years

17.2%

1,745 [1657, 1830]

46.0 [32.2, 60.0]

   2 - 3 years

15.3%

1,226 [1150, 1304]

33.2 [20.7, 45.7]

   3 - 6 years

30.8%

923 [876, 971]

21.9 [14.6, 28.9]

   ≥ 6 years

15.5%

712 [652, 769]

13.1 [5.4, 21.0]

   Unknown

6.2%

1,938 [1786, 2090]

37.2 [16.1, 58.0]

Household income quintile of the neighborhood

   Low

4.7%

1,482 [1329, 1634]

63.5 [32.5, 94.8]

   Medium Low

10.1%

1,559 [1452, 1665]

40.9 [23.7, 57.7]

   Medium

24.1%

1,256 [1194, 1319]

33.6 [23.6, 43.7]

   Medium High

43.1%

1,391[1340, 1438]

29.6 [22.5, 36.6]

   High

18.0%

1,252 [1178, 1322]

32.1 [20.9, 43.6]

Drinking Water Disinfection

   Chlorination

38.7%

1,343 [1293, 1394]

27.7 [20.7, 35.1]

   None

61.3%

1,358 [1319, 1400]

37.6 [30.9, 44.2]

Water System or Subsystem

   Municipal A*: mixed surface (66-96%) & well

27.2%

1,905 [1832, 1977

28.8 [20.0, 37.3]

   Municipal B*: mixed surface (66-96%) & well

8.6%

1,741 [1619, 1865]

29.9 [14.3, 45.8]

   Municipal C*: mixed surface (12-63%) & well

16.2%

949 [882, 1013]

23.4 [13.1, 33.6]

   Municipal D*: well, with added surface water in emergencies & summer

8.8%

1,252 [1150, 1355]

43.1 [24.1, 61.7]

   Municipal E*: well, with added surface water in emergencies & summer

1.5%

829 [627, 1030]

50.7 [1.0, 100]

   Municipal F: well, large systems

14.9%

1,340 [1257, 1421]

54.4 [38.1, 70.6]

   Municipal G: well, small systems

0.4%

412 [142, 679]

0 [0, 216]

   Community well

1.7%

949 [747, 1154]

11.3 [0, 33.5]

   Private well

20.7%

949 [887, 1003]

32.9 [22.1, 43.5]

Sewage Disposal

   Municipal sewer user

52.8%

1,701[1653, 1751]

39.4 [32.3, 46.9]

   Private sewer user

47.3%

971 [930, 1008]

27.0 [20.7, 33.6]

Land Use

   Agricultural

8.3%

1,059 [962, 1157]

32.1 [15.2, 48.7]

   Residential

91.7%

1,380 [1347, 1413]

33.9 [28.8, 39.1]

  1. a Number of physician visits = 7,017 in 189,234,765 person-days of observation
  2. b Number of hospitalizations = 180 in 194,552,383 person-days of observation
  3. * = Systems receiving both well water from municipal wells in the Township and surface water from North Shore Mountain reservoirs. Areas A, B, and C receive mixed water throughout the year; the estimated proportions of surface water listed above are based on 2009 total, peak and minimum flows at central monitoring stations. Areas D and E receive surface water only in emergencies (e.g., system maintenance work) and in peak summer months when well water levels are low. Township personnel indicated that the water distribution network design suggests additional differences between areas that cannot be quantified, such that area A is believed to receive more surface water than area B, and area D is believed to receive more surface water than area E. The proportions of surface water in all five mixed systems vary with rainfall, system water use, and system maintenance.