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Association between keeping pet animals and allergic rhinitis: a case-control study among Japanese university students.

Introduction

Environmental factors are believed to affect the development of allergic diseases (Asher et al., 2006; Strachan, 1989). Pet ownership, especially keeping a dog (Bergroth et al., 2012; Chen et al., 2008) or cat (Celedon et al., 2002; Polk et al., 2004), has been associated with respiratory allergic diseases. Although these associations have been discussed in several review articles (Chen, Tischer, Schnappinger, & Heinrich, 2010; Lodge, Allen, et al., 2012; Takkouche, Gonzalez-Barcala, Etminan, & Fitzgerald, 2008), data regarding the effects of these animals, usually expressed as "risk" or "protection," have been inconsistent. These inconsistencies are thought to be due to the differences in subject age (Holt & Sly, 2009), geographical effects (Asher et al., 2006), avoidance of animals by high-risk subjects (Bertelsen et al., 2010), and study methods used (Chen et al., 2010). Therefore, further studies are required to clarify the association between keeping pets and allergic diseases.

Allergic rhinitis is a major respiratory allergic disease, the prevalence of which is increasing in the general population (Strachan et al., 1997). As allergic rhinitis affects a patient's quality of life (Greiner, Hellings, Rotiroti, & Scadding, 2011) and has significant socioeconomic impact (Hellgren, Cervin, Nordling, Bergman, & Cardell, 2010), methods are required for prevention, as well as for determination of the association between its pathogenesis and environmental factors, including pet animals.

While several comprehensive cohort studies show that early exposure to a pet has protective effects for allergic sensitization (Almqvist et al., 2010; Lodrup Carlsen et al., 2012; Ownby, Johnson, & Peterson, 2002; Wegienka et al., 2011; Wegienka, Johnson, Havstad, Ownby, & Zoratti, 2010), the effects of pets on allergic rhinitis are still unclear (Lodrup Carlsen et al., 2012). This uncertainty might be due in part to the many studies that have evaluated subject exposure to animals over short periods of time only, such as at birth or in early childhood (Bergroth et al., 2012; Chen et al., 2008; Lodge, Lowe, et al., 2012).

Additional studies are therefore necessary to evaluate exposure at later times, especially because allergic rhinitis frequently has an onset at older ages than other allergic diseases. Thus, evidence is needed to determine whether previous experience of keeping pets, from birth to adolescence, is related to the development of allergic rhinitis.

This study evaluated the association between past experience of keeping pets and consequent development of allergic rhinitis using a retrospective epidemiological method. This study focused on allergic rhinitis because of its high worldwide prevalence and the long-term effects of environmental factors on this condition.

Methods

Study Subjects

We recruited first-year students at Shinshu University in central Japan, including 2,164 who enrolled in 2012 and 2,133 who enrolled in 2013. Almost one third of these first-year students lived in the same prefecture as the university, with the remainder coming from other areas. A questionnaire was distributed to all 4,297 first-year students at lectures held by the authors, with 3,614 (84.1%) providing responses. To maintain the age homogeneity of the study population, first-year students over 20 years of age were excluded. In addition, incomplete answers were excluded. In total, 3,061 first-year students ages 18 to 20 years, or 71.2% of all first-year students, were included in the study. The study design and protocol were reviewed and approved by the Committee for Medical Ethics of Shinshu University (approval number 1709).

Questionnaire

The self-administered anonymous survey questionnaire included questions regarding a diagnosis of allergic rhinitis: "Have you ever been diagnosed with allergic rhinitis by a doctor? If yes, please state your age at diagnosis." To make the baseline appearance of allergic rhinitis uniform, the questionnaire asked about the first diagnosis at a medical facility.

The experience of keeping a dog or cat was investigated. In Japan, dogs may be kept inside or outside the home, resulting in a different frequency of exposure for children. Dogs kept inside the home (mostly small-sized dogs) spend their entire time inside the home, except when being walked for toileting and recreation. Dogs kept outside the home rarely enter the home. Cats in Japan are usually kept inside the home. In the present study, keeping a pet was therefore sorted into three categories: dogs inside the home, dogs outside the home, and cats. In addition, the questionnaire included age at first exposure to a pet.

The survey also included demographic factors, including age (number of years), sex (male or female), and family history of allergic rhinitis (yes or no). Participants were also asked about past habits or background factors that have been reported to show associations with allergic rhinitis. For example, differences in air pollution or pollen count between rural and urban districts are thought to affect the development of allergies (Nicolai, 1997; Uchida, Kaneko, & Kawa, 2013); therefore, location of previous hometown region (prefecture) was included in the questionnaire. We asked about number of siblings because large number of siblings is associated with a decrease in allergic diseases (Strachan, 1989). The age of enrollment in daycare also affects the development of allergic diseases (Svanes et al., 2002). Although many children in Japan attend daycare, those who do not attend daycare usually go to kindergarten. To assess the effects of daycare on allergic rhinitis, daycare center attendance (yes or no) was investigated. As the type of fuel used for heating has also been shown to affect allergic diseases (Burr et al., 1999), the questionnaire asked about heating of their homes, whether by coal, oil, or other fuels.

Statistical Analysis

Of the 3,061 students, 761 (24.9%) had been diagnosed with allergic rhinitis and 2,300 (75.1%) had not. To control for background factors (described below) and also to compare effects of pet exposure by age, a case-control design was used in this study. Case and control subjects were matched by six background factors: sex, hometown region, number of siblings, daycare experience, type of fuel used for heating, and family history.

Age was not matched because the study population was uniform, with all subjects 18 to 20 years. Age at onset of allergic rhinitis was assessed by two matching methods: whole matching and onset age-stratified matching. In whole matching, case and control groups each consisted of 570 subjects. As allergic rhinitis first appeared over a wide age range, environmental exposure may have different effects according to age at onset. Therefore, not only age at first animal exposure, but age at onset of allergic rhinitis should be considered. In onset age-stratified matching, subjects were divided into four groups according to age at onset of allergic rhinitis (0-4, 5-9, 10-14, and [greater than or equal to] 15 years).

The age stratified matching was conducted independently from the all-study subjects to avoid using any control subject twice in the study. The four age-stratified groups included 62, 155, 204, and 79 subject pairs, respectively. Finally, both of the matching groups were used for analysis in this study.

The association between previously keeping pet animals and a diagnosis of allergic rhinitis was analyzed statistically. In the whole matched pairs, the number of subjects who began keeping a pet animal was assessed by yearly age, from 0 to 18 years. The proportions of subjects in each age group who kept a pet were compared using the McNemar's test, odds ratio (OR), and 95% confidence interval (95% CI).

In subjects stratified by age at onset, a similar calculation was performed up to the onset age. Thus, subjects who had a pet were placed in the same category, regardless of whether or not they subsequently kept the pet.

In the case group, subjects who brought home a pet after the onset of allergic rhinitis were not counted as keeping a pet. This allocation was based on the hypothesis that previous pet keeping affects the consequent onset of allergic rhinitis. Stata13 software was used for all statistical analyses with p < .05 deemed statistically significant.

Results

The demographic and clinical characteristics of the case and control subjects are shown in Table 1. Age at onset of allergic rhinitis was most frequently 10-14 years, accounting for 40.7% of subjects with allergic rhinitis. Factors were compared among case and control groups. The rates of keeping a dog inside the home, outside the home, and keeping a cat were 8.2%, 19.6%, 12.6%, and 16.8%, 22.3%, 16.7% in case and control groups, respectively.

The effects of previously keeping a pet on the development of allergic rhinitis were determined. The ORs (95% CIs) for allergic rhinitis of keeping a dog inside the home, a dog outside the home, and a cat at age 0 were 2.50 (0.75-10.92), 1.26 (0.70-2.28), and 1.64 (0.73-3.83), respectively, by whole matching (Table 2), although these differences were not statistically significant. The ORs, however, decreased with increasing subject age. At age 18 years, the ORs (95% CIs) for allergic rhinitis of keeping a dog inside the home, a dog outside the home, and a cat were 0.44 (0.30-0.65), 0.60 (0.43-0.83), and 0.51 (0.35-0.73), respectively.

To examine differences in age at onset, ORs were evaluated in the age-stratified matching groups. Among families of subjects diagnosed with allergic rhinitis at 0-4 years old, none had kept a pet dog inside the home. The same was true of control subjects matched for age. Therefore, we could not analyze ORs among these groups. Although the ORs ranged widely and some were not below 1.0 at later periods, the ORs for allergic rhinitis of keeping all three categories of pets showed a similar tendency as that of the whole matching group, of decreasing with age (Tables 3-5).

The estimated ORs and 95% CIs for allergic rhinitis of keeping all three types of animals are shown in Figure 1A-C. At age 0 years, the ORs for allergic rhinitis of keeping a dog inside the home, a dog outside the home, and a cat were >1.0, but decreased with increasing age. The ORs for keeping a dog inside the home, a dog outside the home, and a cat fell below 1.0 at ages 10, 4, and 11 years, respectively. Keeping a pet of all three types at around age 0 years was found to be a risk factor for the later development of allergic rhinitis, but in time changed to a protective effect with increasing age.

Discussion

In general, allergic diseases might be caused by both genetic and environmental factors (Portelli, Hodge, & Sayers, 2015). Allergic rhinitis is a fairly common disease that is often associated with other comorbidities, including asthma, which also has a high first year of life diagnosis. Environmental factors that affect the prognosis of allergic diseases have long been studied (Strachan, 1989). To tease apart the associations between and among genetic and environmental factors and allergic diseases is difficult; therefore longitudinal epidemiologic studies are necessary. Under these circumstances, in the present study, we focused only on examining the association between allergic rhinitis and pets.

This study evaluated the association between previous experience of keeping a pet and a diagnosis of allergic rhinitis among first-year university students. To minimize sampling bias and to evaluate the effect of animal exposure from birth to adolescence, case-control matching was performed. At age 0 years, the ORs for allergic rhinitis of keeping a dog or cat were all >1.0, with these ORs decreasing with increasing subject age, falling below 1.0 in the entire matching group for all three classes of pet animals. Thus, the effects of previous experience of keeping a pet animal on the development of allergic rhinitis were different soon after birth and at later times.

Cohort studies have reported that keeping pets can protect against the development of allergic rhinitis. For example, the OR for allergic rhinitis at 4 years in subjects exposed to pets at birth was 0.6 (Nafstad, Magnus, Gaarder, & Jaakkola, 2001), and previous cat ownership was associated with a reduced risk of current allergic rhinitis (OR = 0.41) at age 5 years (Perzanowski et al., 2008). In these studies, however, subjects were evaluated at 4 or 5 years of age, which is below the age at which symptoms of allergic rhinitis are usually first noted. Therefore, these ORs might change if evaluated longitudinally.

Evaluation of older subjects showed that keeping a cat in the home during the first year of life increased the risk of allergic rhinitis (OR = 2.21) in children ages 6-12 (Tamay et al., 2007). A collaborative European cohort study found no significant association between early animal exposure and allergic rhinitis among school-aged children (Lodrup Carlsen et al., 2012). Thus, the effects of pet exposure after birth might differ in subjects evaluated during early childhood and in those evaluated at a later period.

The effects of current pet exposure on allergic rhinitis have also been found to differ. For example, current exposure to a cat or dog did not have a significant effect on allergic rhinitis (OR = 1.0) in children ages 7-10 (Wickens et al., 2002). The risk ratios for allergic rhinitis were found to be 0.71 in children age 6 years with a current pet (Kurosaka et al., 2006), and 0.6 in children ages 10-11 who currently had a cat (Braback, Kjellman, Sandin, & Bjorksten, 2001).

Therefore, keeping a pet in later childhood may have a protective effect against allergic rhinitis. Thus, these results indicated that the effects of a pet on allergic rhinitis vary according to the timing of animal exposure or the age at which subjects are evaluated. Although pets have been regarded as increasing or reducing the risk of development of allergic rhinitis, our finding, that the effects of pets change, might explain the discrepancies in previous studies.

Although the effects on allergic rhinitis across the three pet categories were mostly consistent, some slight differences were seen. This study evaluated two categories of keeping a dog (i.e., indoor or outdoor). Keeping a dog inside the home showed a slightly higher OR for allergic rhinitis, similar to that for keeping a cat. As exposure to dander or dust mites is greater inside than outside the home, allergic diseases can more easily develop in subjects who have pets inside the home. This observation is similar to the observation that house dust is a general risk factor for several allergic diseases (Nurmatov, van Schayck, Hurwitz, & Sheikh, 2012). Thus, it may be necessary to consider environmental factors when investigating the effects of pet animals on allergic diseases.

This study had several limitations. First, because this study was based on a self-administered questionnaire survey, recall bias could not be excluded. This bias might be especially true in the cases where recall was of memories of early childhood. Moreover, laboratory data, including intensity of allergen exposure and serum IgE concentration, could not be determined. These limitations might have resulted in an overestimation of the association between pets and allergic rhinitis. As the effect curves were similar for the three pet classifications, however, the results probably are reliable.

Second, duration of pet animal exposure might vary between matched pairs. We only hypothesized that previous pet keeping was associated with the consequent onset of allergic rhinitis, so we did not control for duration of pet animal exposure. Indeed it is probably impossible to find enough subjects in a population to completely eliminate this confounding variable. By using age-stratified matching, however, we could adjust and control for this variable as much as possible in our data set. This difference might cause an increase in the odds ratio between case and control groups. For exposure duration to be equivalent and analyzed in detail, a prospective and large sample cohort study is necessary.

Third, the study did not adjust for several environmental factors. Passive smoking, for example, may affect the development of allergic rhinitis (Biagini et al., 2006). Moreover, underlying allergic diseases that might affect the subsequent avoidance of pets (Bertelsen et al., 2010) was not determined. Moreover, allergic diseases often show higher prevalence in urban areas compared to rural areas (Nicolai, 1997). We matched subjects for previous hometown prefecture to avoid the district effect in this study; however, the effect might remain because prefectures are relatively large. Thus, the possibility of confounding factors could not be ruled out.

Fourth, although keeping pet cats and dogs was evaluated separately, this study did not assess the simultaneous keeping of multiple pets, thereby overestimating the effects of pet animals on allergic rhinitis. Fifty-two (4.4%) of the 1,194 individuals with pets, however, began keeping multiple animals simultaneously for the first time, suggesting that the effect of multiple pets was small.

Fifth, this study assessed only the association between pet animals and allergic rhinitis. Therefore, the pathogenesis of allergic rhinitis was not clarified. Moreover, the study population consisted only of university students, limiting the generalization of these study results to other populations.

Conclusions

The data from this study suggested that keeping a dog or cat soon after birth increases the risk of the child subsequently developing allergic rhinitis. This effect, however, was likely to be reduced when pets were introduced later in childhood, with keeping pets even showing a protective effect against allergic rhinitis. This study may contribute to a greater understanding of the inconsistencies in previous studies on the effects of pet animals and allergic diseases. Further studies are warranted to clarify the effects of pet animals on allergic diseases.

[FIGURE 1 OMITTED]

Mitsuo Uchida, MD, PhD

Minoru Kaneko, MD, PhD

Shigeyuki Kawa, MD, PhD

Center for Health, Safety, and

Environmental Management

Shinshu University

Acknowledgement: We acknowledge Tomoko Fujimura, Hiroko Hayashi, Naomi Yuzawa, Kiyomi Tanaka, Yoshinobu Shinkai, Kyoko Inuura, Kazuki Nagai, Yoko Watanabe, and Koichi Asawa for their assistance in the collection and analysis of data.

Corresponding Author: Mitsuo Uchida, Center for Health, Safety, and Environmental Management, Shinshu University, 3-1-1 Asahi, Matsumoto 390-8621, Japan.

E-mail: uchida01@shinshu-u.ac.jp.

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TABLE 1

Characteristics of Case and Control Subjects in
First-Year University Students

                           Case

Factor               (n = 570)   (%)

Onset age
  0-4                   72       12.6
  5-9                   183      32.1
  10-14                 232      40.7
  15-18                 83       14.6
Sex
  Male                  385      67.5
  Female                185      32.5
Sibling number
  1                     43       7.5
  2                     322      56.5
  3                     186      32.6
  4 or more             19       3.3
Experience of
daycare center
  Yes                   290      50.9
  No                    280      49.1
Family history of
allergic rhinitis
  Yes                   74       13.0
  No                    496      87.0
Habitual heating
  Fuels or coal         440      77.2
  Others                130      22.8
Dog inside
the home
  Yes                   47       8.2
  No                    523      91.8
Dog outside
the home
  Yes                   112      19.6
  No                    458      80.4
Cat
  Yes                   72       12.6
  No                    498      87.4

                          Control       p- Value *

Factor               (n = 570)   (%)

Onset age
  0-4
  5-9
  10-14
  15-18
Sex
  Male                  385      67.5    1.00
  Female                185      32.5
Sibling number
  1                     43       7.5     1.00
  2                     322      56.5
  3                     186      32.6
  4 or more             19       3.3
Experience of
daycare center
  Yes                   290      50.9    1.00
  No                    280      49.1
Family history of
allergic rhinitis
  Yes                   74       13.0    1.00
  No                    496      87.0
Habitual heating
  Fuels or coal         440      77.2    1.00
  Others                130      22.8
Dog inside
the home
  Yes                   96       16.8    <.01
  No                    474      83.2
Dog outside
the home
  Yes                   127      22.3     .28
  No                    443      77.7
Cat
  Yes                   95       16.7     .05
  No                    475      83.3

* Chi square test was used for categorical data.

TABLE 2

Association Between Past Experience of Keeping Pet Animals
and Allergic Rhinitis at Several Ages in Whole Matching
Group (N = 1,140, 570 Control and 570 Matched Case Subjects)

             Dog Inside the Home

Age   Case   Control    OR      95% CI

 0     10       4      2.50   0.72, 10.92
 1     10       4      2.50   0.72, 10.92
 2     11       5      2.20   0.70, 8.08
 3     12       5      2.40   0.79, 8.70
 4     14       5      2.80   0.95, 9.93
 5     16       8      2.00   0.81, 5.40
 6     24      15      1.60   0.81, 3.28
 7     27      22      1.23   0.67, 2.26
 8     32      30      1.07   0.62, 1.84
 9     36      32      1.13   0.68, 1.89
10     40      42      0.95   0.60, 1.51
11     40      45      0.89   0.56, 1.40
12     41      54      0.75   0.48, 1.16
13     43      60      0.71   0.46, 1.07
14     44      70      0.61   0.40, 0.91
15     45      77      0.56   0.37, 0.83
16     46      86      0.49   0.33, 0.73
17     47      92      0.46   0.31, 0.69
18     47      96      0.44   0.30, 0.65

             Dog Outside the Home

Age   Case   Control    OR      95% CI

 0     30      24      1.26   0.70, 2.28
 1     34      25      1.38   0.79, 2.43
 2     36      33      1.10   0.65, 1.87
 3     40      37      1.09   0.66, 1.79
 4     43      45      0.95   0.60, 1.50
 5     51      50      0.98   0.64, 1.50
 6     53      63      0.83   0.56, 1.23
 7     61      75      0.79   0.54, 1.15
 8     70      83      0.81   0.56, 1.17
 9     73      89      0.78   0.54, 1.12
10     80      100     0.75   0.53, 1.06
11     82      106     0.72   0.51, 1.01
12     84      112     0.70   0.50, 0.97
13     84      115     0.67   0.48, 0.93
14     84      119     0.64   0.46, 0.89
15     85      122     0.63   0.46, 0.88
16     85      125     0.61   0.44, 0.84
17     85      126     0.61   0.44, 0.84
18     85      127     0.60   0.43, 0.83

                    Cat

Age   Case   Control    OR      95% CI

 0     18      11      1.64   0.73, 3.83
 1     21      12      1.75   0.82, 3.90
 2     22      15      1.50   0.73, 3.19
 3     28      16      1.86   0.93, 3.84
 4     31      18      1.81   0.95, 3.57
 5     33      21      1.63   0.89, 3.06
 6     36      23      1.62   0.91, 2.94
 7     40      25      1.65   0.96, 2.90
 8     41      28      1.52   0.89, 2.63
 9     44      33      1.38   0.83, 2.30
10     47      41      1.17   0.73, 1.87
11     47      49      0.95   0.61, 1.49
12     47      55      0.84   0.54, 1.29
13     47      58      0.79   0.52, 1.21
14     50      65      0.75   0.50, 1.12
15     50      71      0.68   0.46, 1.01
16     51      80      0.61   0.41, 0.89
17     51      92      0.52   0.36, 0.76
18     51      95      0.51   0.35, 0.73

OR = odds ratio; CI = confidence interval.

TABLE 3
Association Between Past Experience of Keeping a Dog
Inside the Home and Allergic Rhinitis in Onset
Age Stratified Group

                0-4 Years Onset Group

         Case      Control
Age     n = 62     n = 62     OR        95% CI

0         0           0       NA
1         0           0       NA
2         0           0       NA
3         0           0       NA
4         0           0       NA
5
6
7
8
9

                5-9 Years Onset Group

         Case      Control
Age    n = 155     n = 155    OR        95% CI

0         4           1      4.00     0.40, 197.0
1         4           1      4.00     0.40, 197.0
2         4           1      4.00     0.40, 197.0
3         4           1      4.00     0.40, 197.0
4         5           1      5.00     0.56, 236.5
5         5           2      2.50     0.41, 26.25
6         8           2      4.00     0.80, 38.67
7         9           2      4.50     0.93, 42.80
8         10          4      2.50     0.72, 10.92
9         11          4      2.75     0.81, 11.84

                10-14 Years Onset Group

         Case      Control
Age    n = 204     n = 204    OR        95% CI

0         3           2      1.50     0.17, 18.00
1         3           2      1.50     0.17, 18.00
2         3           2      1.50     0.17, 18.00
3         4           2      2.00     0.29, 22.10
4         4           2      2.00     0.29, 22.10
5         5           2      2.50     0.41, 26.25
6         9           5      1.80     0.54, 6.84
7         11          7      1.57     0.56, 4.78
8         14          9      1.56     0.63, 4.07
9         16          9      1.78     0.74, 4.56
10        18         11      1.70     0.74, 4.15
11        18         11      1.70     0.74, 4.15
12        18         14      1.31     0.60, 2.93
13        19         15      1.31     0.60, 2.93
14        20         20      1.00     0.49, 2.04
15
16
17
18

                15-18 Years Onset Group

         Case      Control    OR        95% CI
Age     n = 79     n = 79

0         3           1      3.00     0.24, 157.5
1         3           1      3.00     0.24, 157.5
2         3           1      3.00     0.24, 157.5
3         3           1      3.00     0.24, 157.5
4         4           1      4.00     0.40, 197.0
5         5           1      5.00     0.56, 236.5
6         6           1      6.00     0.73, 276.0
7         6           4      1.50     0.36, 7.23
8         6           4      1.50     0.36, 7.23
9         7           4      1.75     0.44, 8.15
10        8           4      2.00     0.54, 9.08
11        8           4      2.00     0.54, 9.08
12        9           4      2.25     0.63, 10.00
13        10          5      2.25     0.63, 10.00
14        10          5      2.25     0.63, 10.00
15        11          7      1.67     0.55, 5.58
16        12          7      1.83     0.62, 6.04
17        13          7      2.00     0.69, 6.49
18        13          8      1.71     0.62, 5.14

NA = not applicable; OR = odds ratio;
CI = confidence interval.

TABLE 4

Association Between Past Experience of Keeping a Dog
Outside the Home and Allergic Rhinitis in Onset Age
Stratified Group

                   0-4 Years Onset Group

         Case       Control      OR       95% CI
Age     n = 62       n = 62

0         1            1        1.00   0.01, 78.50
1         1            1        1.00   0.01, 78.50
2         1            2        0.50    0.01, 9.60
3         1            2        0.50    0.01, 9.60
4         1            2        0.50    0.01, 9.60
5
6
7
8
9

Age                5-9 Years Onset Group

         Case       Control      OR       95% CI
       n = 155      n = 155

0         7            4        1.75    0.44, 8.15
1         8            5        1.60    0.46, 6.21
2         8            7        1.14    0.36, 3.70
3         11           10       1.10    0.42, 2.89
4         11           12       0.92    0.37, 2.27
5         12           14       0.86    0.36, 2.00
6         13           19       0.68    0.31, 1.46
7         15           20       0.74    0.34, 1.55
8         16           21       0.75    0.36, 1.54
9         16           23       0.67    0.31, 1.37

Age                10-14 Years Onset Group

         Case       Control      OR       95% CI
       n = 204      n = 204

0         12           12       1.00    0.37, 2.68
1         15           13       1.18    0.49, 2.91
2         15           16       0.93    0.40, 2.13
3         16           19       0.82    0.38, 1.78
4         18           21       0.84    0.41, 1.73
5         23           23       1.00    0.52, 1.92
6         23           29       0.78    0.42, 1.43
7         26           34       0.72    0.39, 1.31
8         30           37       0.77    0.43, 1.37
9         32           40       0.76    0.43, 1.31
10        35           42       0.79    0.46, 1.36
11        36           43       0.79    0.46, 1.36
12        38           43       0.85    0.50, 1.44
13        38           44       0.82    0.49, 1.40
14        38           46       0.78    0.46, 1.31
15
16
17
18

                   15-18 Years Onset Group

         Case       Control      OR       95% CI
Age     n = 79       n = 79

0         4            2        2.00   0.29, 22.11
1         4            2        2.00   0.29, 22.11
2         5            4        1.25    0.27, 6.30
3         5            7        0.67    0.14, 2.81
4         5            8        0.50    0.08, 2.34
5         7            8        0.83    0.20, 3.28
6         8            9        0.86    0.24, 2.98
7         9            11       0.78    0.25, 2.35
8         13           12       1.13    0.39, 3.35
9         14           12       1.25    0.44, 3.64
10        18           12       1.75    0.69, 4.81
11        19           12       1.88    0.75, 5.11
12        19           12       1.88    0.75, 5.10
13        19           12       1.88    0.75, 5.10
14        19           12       1.88    0.75, 5.10
15        20           12       2.00    0.80, 5.40
16        20           13       1.78    0.74, 4.56
17        20           13       1.78    0.74, 4.56
18        20           14       1.60    0.68, 3.94

OR = odds ratio; CI = confidence interval.

TABLE 5

Association Between Past Experience of Keeping a Cat
and Allergic Rhinitis in Onset Age Stratified Group

                   0-4 Years Onset Group

         Case       Control
Age     n = 62       n = 62       OR        95% CI

0         0            3           0      0.00, 2.42
1         0            3           0      0.00, 2.42
2         0            3           0      0.00, 2.42
3         0            3           0      0.00, 2.42
4         0            3           0      0.00, 2.42
5
6
7
8
9

                   5-9 Years Onset Group

         Case       Control
Age    n = 155      n = 155       OR        95% CI

0         6            2         3.00     0.54, 30.39
1         8            2         4.00     0.80, 38.67
2         8            3         2.67     0.64, 15.60
3         13           3         4.33     1.19, 23.70
4         14           4         3.50     1.10, 14.60
5         15           5         3.00     1.04, 10.55
6         16           5         3.20     1.12, 11.17
7         16           5         3.20     1.12, 11.17
8         16           7         2.29     0.89, 6.57
9         16           9         1.78     0.74, 4.56

                   10-14 Years Onset Group

         Case       Control       OR        95% CI
Age    n = 204      n = 204

0         9            6         1.50     0.48, 5.12
1         9            6         1.50     0.48, 5.12
2         10           8         1.29     0.43, 4.06
3         11           8         1.43     0.49, 4.42
4         13           8         1.71     0.62, 5.14
5         14           10        1.44     0.57, 3.83
6         14           10        1.44     0.57, 3.83
7         16           12        1.36     0.59, 3.28
8         17           14        1.23     0.56, 2.78
9         19           16        1.21     0.56, 2.66
10        21           19        1.11     0.55, 2.29
11        21           22        0.95     0.48, 1.88
12        21           24        0.86     0.44, 1.67
13        21           24        0.86     0.44, 1.67
14        22           27        0.80     0.42, 1.50
15
16
17
18

Age                15-18 Years Onset Group

         Case       Control       OR        95% CI
        n = 79       n = 79
0         1            1         1.00     0.01,78.50
1         2            2         1.00     0.07, 13.80
2         2            2         1.00     0.07, 13.80
3         2            3         0.67     0.06, 5.82
4         2            3         0.67     0.06, 5.82
5         2            3         0.67     0.06, 5.82
6         2            3         0.67     0.06, 5.82
7         3            3         1.00     0.13, 7.47
8         3            4         0.75     1.10, 4.43
9         4            6         0.67     1.38, 2.81
10        4            8         0.50     0.11, 1.87
11        4            12        0.33     0.08, 1.10
12        4            13        0.31     0.07, 1.00
13        4            13        0.31     0.07, 1.00
14        5            14        0.36     0.10, 1.05
15        5            14        0.36     0.10, 1.05
16        6            15        0.40     0.13, 1.09
17        6            16        0.38     0.12, 1.01
18        6            16        0.38     0.12, 1.01

OR = odds ratio; CI = confidence interval.
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Article Details
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Title Annotation:INTERNATIONAL PERSPECTIVES
Author:Uchida, Mitsuo; Kaneko, Minoru; Kawa, Shigeyuki
Publication:Journal of Environmental Health
Article Type:Report
Geographic Code:9JAPA
Date:Oct 21, 2016
Words:6537
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