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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.
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