Main analyses

As signalled earlier, the main analyses for the determinants model are presented in three sections . First, the results of a repeated measures MANOV A are presented, which provide information on the stability of mean scores of each variable over time. Second, all bivariate relationships among variables are computed. Finally, the research questions are addressed at the multivariate level using multiple regression analysis.

(i) Univariate considerations

A repeated measures MANOVA was conducted on variables in the determinants model that were assessed at both times. The results are presented in Table 3 . The overall F value for this analysis was significant (F = 9.07, P < . 00 1 ) suggesting some change over

time. Specific differences were found for perceptions of the average intensity over the last six months, frequency of attacks, and self-rated seriousness.

Table 3

Means and standard deviations of determinants and seriousness measures, assessed at both times (N = 302).

Time 1 Time 2

Variable Mean SD Mean SD F

Prevalence 75 .95 2 1 . 1 7 74. 54 22. 54 1 . 53 Treatability 77 .42 2 1 .08 76.73 1 9 . 78 .37 Intensity (6 months) 2 . 4 1 1 .3 1 2 . 14 1 . 16 1 7. 02 * Frequency of attacks 2 . 55 1 .32 2 . 24 1 .30 25 .69 * Self-rated seriousness 3 .22 1 .30 2 . 86 1 .23 37 .75 * Frequency of symptoms 78. 90 20. 75 78 . 14 23 . 25 . 59 Number of symptoms 24. 50 6 . 85 24. 0 1 7 .65 3 .55 * p < .00 1

Consistently, the direction of these differences indicates that asthma was perceived to be more serious at Time 1 (Spring) compared to Time 2 (Autumn) . A comparison of the magnitude of each difference with its corresponding total score reveals that the differences are not large. There were no differences in the prevalence or treatability variables across time. Despite the difference found in self-rated seriousness, there were no differences in the symptom measures of seriousness. Although MAN OVA does not analyze changes in variability, the standard deviations in Table 3 are stable.

(ii) Cross-sectional bivariate relationships

Before examining the research questions using multiple regression techniques, three preliminary bivariate analyses were conducted. These were (i) the intercorrelations among the independent variables, comprised of the determinants and control variables (remembering that RDS is a determinant), (ii) the intercorrelations among the dependent variables, comprised of the seriousness measures, and (iii) the correlations between the independent and dependent variables.

Table 4 presents the cross-sectional intercorrelations among the independent variables, at both times. The reader is reminded that only replicated results are reported in the text. In general, associations among the determinants were weak. Asthmatics who perceived their illness to have higher prevalence judged it to be more treatable. Asthma was also viewed to be more treatable when it was perceived to have lower average intensity over entire history and over the last six months, and when the frequency of attacks was judged to be lower. Longer term asthmatics viewed their illness to have higher average intensity over entire history . The two average intensity measures were only weakly positively correlated, indicating that they are tapping separate aspects of average intensity . Asthmatics who perceived their illness to have higher average intensity over entire history and over the last six months perceived a. higher frequency of attacks. In fact, average intensity over the last six months and

Table 4

Intercorrelations among determinants, RDS, and control variables at Time 1 (N =330) and Time 2 (N =322).

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

1 Prevalence . 1 2* - . 07 . 09 . 04 . 02 - . 1 7 * * - . 1 3 * - . 23 * * * .04 -.05 . 00

2 Treatability . 1 6* * - . 0 1 - . 2 1 *** -.28* * * - . 29* * * - . 03 . 0 1 . 02 . 1 1 * .08 .09

3 Duration - . 1 8 * * - . 0 1 . 20*** .03 . 1 0 . 1 1 * . 25 * * * . 2 1 * * * . 00 - . 06 . 1 4*

4 I ntensity (entire history) . 00 - . 1 4* . 1 7 * * . 36* * * .43 * * * - . 04 . 0 1 - . 07 -. 05 -. 05 - . 04 5 Intensity (6 months) . 0 1 - . 39* * * .08 . 3 1 * ** . 6 1 * * * - . 03 -.07 - . 06 . 03 .02 - . 08

6 Frequency (attacks) . 03 - . 39* * * .09 .28 *** . 64* * * - . 03 -. 05 - . 09 - . 04 - . 06 - . 06

7 Repressive defence style - . 1 5 * * - . 0 1 . 1 0 -.04 - . 04 - . 1 1 .29* * * . 1 1 * - . 1 8* * -.08 . 1 3 *

8 Age - . 1 2 * .02 . 24* * * - . 04 - . 09 - . 1 3 * . 3 1 * * * . 2 1 * * * - . 3 1 * * * - . 1 3 * . 22 * * * 9 Gender - . 24* * * -.03 . 20* * * - . 1 2 * -.08 - . 07 .09 . 1 9* * .06 . 1 1 * . 06 10 Education 1 -.01 .00 . 00 - . 0 1 . 0 1 . 05 - . 1 4* - . 30* * * .08 . 39* * * - . 03 1 1 Education 2 - . 1 2* . 1 0 - . 05 .00 - . 08 - . 09 - . 04 - . 08 . 1 1 .40* * * .02 1 2 Marital status . 0 1 . 07 . 1 2 * - . 07 -.07 - . 09 . 1 2 * .20* * * . 04 - . 05 .01 * p < .05 * * p < . 0 1 * * * p < .00 1

Notes : 1. Time 1 intercorrelations appear above diagonal, Time 2 appear below diagonal .

frequency of attacks correlated at r = . 6 1 at Time 1 and r= . 64 at Time 2 . Asthmatics with higher repression scores viewed their asthma to be less prevalent compared to asthmatics with lower repression scores, but repression scores were not associated with any other determinant variables.

Some weak relationships between the determinants and the control variables were found. Younger asthmatics viewed their illness to be more prevalent compared to older asthmatics, as did female asthmatics compared male asthmatics. Longer term asthmatics were generally older rather than younger individuals, and also tended to be women rather than men. They also were more likely to have a partner compared to shorter term asthmatics. Asthmatics with higher repression scores were generally older rather than younger individuals, they tended to be less educated rather than more educated, and they tended to have a partner rather than not.

Some intercorrelations were found among the control variables. Older asthmatics tended to be women rather than men, they tended to be less educated rather than more educated, and they were more likely to have a partner compared to younger asthmatics .

Table 5

Intercorrelations among the seriousness measures at Time 1 (N =367) and Time 2 (N =374).

Self-rated Frequency of Number of

senousness symptoms symptoms

Self-rated seriousness . 44* . 40*

Frequency of symptoms .48* .74*

Number of symptoms .48* . 77*

* p < .00 1

Table 5 presents the cross-sectional intercorrelations among the dependent variables, at both times. These were comprised of the three measures of seriousness; self-rated seriousness, frequency of symptoms, and number of symptoms . Relationships among these measures were all moderate to strong. Asthmatics who perceived their illness to have higher self-rated seriousness were those who experienced either a higher frequency of symptoms or a larger number of symptoms. In passing, these findings provide some support for the study assumption that number and frequency of symptoms are seriousness measures. The symptom measures, both derived from the ASC data, were strongly associated. This indicates that asthmatics who reported a higher number of symptoms also reported a higher frequency of symptoms, and vice

versa.

Table 6

Correlations between detenninants, control variables and seriousness measures at Time 1 (N = 303) and Time 2 (N = 3 15).

Self-rated seriousness Frequency of symptoms Number of symptoms

Time 1 Time 2 Time 1 Time 2 Time 1 Time 2

Prevalence . 1 1 .09 . 1 2* . I S** .07 . 12*

T reatab it i ty -.2S*** - . 3 1 *** - . 14* -. I S * * - . 12* - .24* * *

Duration . I S * * .07 - .02 .02 .02 - . 0 1

Intensity (entire history) . 62*** . S I ** * .40*** .3S*** . 30*** . 29 * * *

Intensity (6 months) .43 * * * .S3*** .34*** . 3 1 *** . 24*** . 3 3 * * * Frequency (attacks) .44*** .46** * . 3 1 * * * . 37*** . 30*** . 34*** RDS -.OS - . 0 1 -.2S*** -.2 1 *** - .2S* * * - . 1 9* * Age . 0 1 .00 - . 14* -. 12* - . 07 - . I S * * Gender - . 1 2* - . I S * * - . 20* * * - . 1 8 * * - .23 * * * -.22*** Education 1 .00 -.08 - .06 .03 - . 0 1 .04 Education 2 - . 0 1 -.09 - .06 -.04 -.09 - . 10 Marital Status .00 - . 1 1 - . 12* -. 10 - .09 -. 1 0 * p < .OS * * p < .O I * * *p < .00 1

Table 6 presents the bivariate relationships between the determinants, control variables and seriousness measures, at both times. In general, weak to moderate associations were found between the determinants and seriousness. Prevalence positively related to frequency of symptoms, but was unrelated to self-rated seriousness and number of symptoms. As such, asthmatics who viewed their illness to be more prevalent reported a higher frequency of symptoms. Asthma was perceived to be more treatable when it was viewed to be less serious. This was found for all the seriousness measures. Three aspects of asthma history (average intensity over entire history, average intensity over the last six months, and frequency of attacks) were positively correlated with each of the seriousness measures. The remaining measure of asthma history, duration, was unrelated to seriousness. RDS showed a clear pattern of relationships with seriousness. Asthmatics with higher repression scores reported a lower frequency of symptoms and fewer symptoms than those with lower repression scores, but repression was unrelated to self­ rated seriousness.

Some relationships were found between the control variables and seriousness . Younger asthmatics reported a higher frequency of symptoms compared to older asthmatics. There were gender differences in all the seriousness measures. Women viewed asthma to be more serious than men. Overall , it can be noted that many of the relationships are stable over time.

(iii) Cross-sectional multivariate relationships

Next, hierarchical multiple regression analysis was used to analyze the relationships in the determinants model . Six regression analyses were run, since there are three dependent variables (self-rated seriousness, frequency of symptoms, and number of symptoms) and two measurement points. For each regression, this involved entering the determinants and control variables on the first step, and the product variables for RDS and each of the determinants on the second step (see Section 2 .6) . The results of these analyses are

presented in Table 7 .

In Table 7, and all other tables of multiple regression results, both standardized and unstandardized slopes are presented. Presenting both types of slope permits an examination of replication of relationships by comparing unstandardized slopes, and an examination of the relative magnitude of effects by comparing standardised slopes within any particular analysis.

Overall, the main variables met with some success in explaining seriousness, particularly self-rated seriousness. The main effects accounted for 48 % of the variance in self-rated seriousness at Time 1 , and 43 % at Time 2 . They were somewhat less successful in explaining the variance in frequency of symptoms or number of symptoms, at both times. They explained 27 % of the variance in frequency of symptoms at Time 1 , and 23 % at Time 2 ; and they accounted for 1 8 % of the variance in number of symptoms at Time 1 , and 2 1 % at Time 2 .

Again, the reader is reminded that only replicated results are reported in the text. Few relationships emerged between the determinants and seriousness. Prevalence was not a determinant of seriousness, and the analyses also revealed that treatability and seriousness were unrelated. As such, they show that the bivariate associations between treatability and seriousness were confounded, probably by one or more of the asthma history variables. Of the asthma history variables, average intensity over entire history was associated with all the seriousness measures. Specifically, asthmatics who perceived their illness to have higher average intensity over entire history viewed it to be more serious. Asthmatics who judged their asthma to have higher average intensity over the last six months perceived it to have higher self-rated seriousness, but average intensity over the last six months was unrelated to the symptom measures of seriousness. Frequency -of attacks also determined self-rated seriousness, but was unrelated to the symptom

Table 7

Regression coefficients, adjusted R', and R' change for regressions of seriousness on determinants and control variables at Time 1 and Time 2 . Seriousness variable Self-rated seriousness Frequency of symptoms Number of symptoms

Time 1 Time 2 Time 1 Time 2 Time 1 Time 2

N = 3 1 2 N = 322 N = 3 1 8 N = 3 1 5 N =330 N = 322

Independent variables Beta B Beta B Beta B Beta B Beta B Beta B

Step 1

Prevalence .046 0.003 .096 0.005* .003 0.003 . 1 06 0 . 1 1 1 * -.019 -0.006 .05 1 0 . 0 1 8

Treatability -.045 -0.284 -.087 -0.006 - . 006 -0.006 -.003 -0.004 -.008 -0.003 -.074 -0.03 1

Duration (entire history) .049 0.004 -.022 -0.002 - .02 1 -0.027 .01 1 0.0 1 7 - . 0 1 5 -0.006 -.0 1 3 -0.006

Intensity (entire history) .499 0. 530** * . 378 0.368* * * . 306 5 . 248*** . 248 4.695 * * * . 179 1 .0 10** . 1 83 1 . 1 42***

Intensity (6 months) . 1 88 0 . 1 80*** . 277 0.286*** . 179 2 . 770** .080 1 .636 .078 0.400 . 1 14 0 .759

Frequency (attacks) . 1 1 1 0. 1 10* . 140 0. 1 33* .039 0 . 635 .2 1 3 3 . 964* * . 1 34 0.706* . 109 0.658

Repressive defence style -.035 -0.006 .04 1 0.006 -.229 -0.596*** -. 1 39 -0.423 * * - .24 1 -0.205 * * * -. 1 24 -0. 125*

Age .077 0.006 .06 1 0.005 - .058 -0.074 .003 0.004 .045 0.0 1 9 - .0 1 8 -0.009

Gender -.087 -0.236 -.075 -0. 1 89 - . 1 03 -4.479* -.093 -4.607 - . 1 65 -2. 355** -. 1 58 -2.573 * *

Education 1 .058 0.244 -.03 1 -0. 1 2 1 - .086 -5 .778 .0 1 9 1 .473 .030 0.658 .087 2 . 1 86

Education 2 .025 0.065 . 000 0.000 - .050 -2. 1 1 3 -.0 1 1 -0.54 1 - .079 - 1 .099 -.078 - 1 .244

Marital Status .032 0.090 -.050 -0. 1 35 -.044 - 1 .98 1 -.042 -2 .2 1 1 - .034 -0.506 -.040 -0.697

Adj R'= .477 Adj R'= .433 Adj R' = .274 Adj R' = .228 Adj R' = . 1 84 Adj R'= .209

F( 1 2.299) =24.60*** F( 1 2 , 309) = 2 1 .45 *** F( l 2 ,305) = 1 0.97*** F( l 2,302) = 8 . 74*** F( 12,3 1 7) =7 . 1 8* * * F( l 2 , 309) = 8 .08*** Step 2

RDS x Prevalence .006 0.000 -.003 0.000 .085 0.009 .0 1 8 0 .002 .053 0.002 - .04 1 - 1 . 634

RDS x Treatability .033 0.000 -. 1 1 3 -0.00 1 * .075 0.0 1 1 .069 0.012 .012 0.00 1 .060 0.003

RDS x Duration -.062 -0.00 1 -.045 0.000 .059 0.009 .014 0.003 .022 0.00 1 -.029 -0.002

RDS x Intensity (entire history) - . 042 -0.005 -.076 -0. 009 - . 089 -0. 1 83 -.068 -0. 1 58 - .052 -0.035 -.034 -0.027

RDS x Intensity (6 months) -.026 -0.003 .006 0.00 1 - .066 -0. 123 . 145 0.378* - .022 -0. 0 1 4 .035 0.029 RDS x Frequency .060 0.008 -.049 -0.006 .084 0. 1 74 -.095 -0. 240 . 0 1 8 0.0 1 2 -.026 -0.022

Adj R' = .474 Adj R' = .44 1 Adj R' = .287 Adj R' = .232 Adj R' = . 1 75 Adj R' = . 200

F(1 8,293) = 1 6. 60*** F(1 8 ,303) = 1 5 .09*** F( 1 8,299) = 8 . 10*** F( l 8,296) =6.26*** F( 1 8 ,3 1 1 ) = 4 . 88*** F( 1 8,303) = 5 .46***

R' change = .008 R' change = .0 1 8 R ' change = .026 R' change = .0 1 8 R' change = .006 R' change = .006

F change =0.80 F change = I . 74 F change = 1 .95 F change = 1 .22 F change = 0.43 F change =0.42

measures. Asthmatics who perceived a higher frequency of attacks viewed asthma to have higher self-rated seriousness. The length of time asthmatics have had asthma did not influence seriousness. Consistent with the bivariate findings, asthmatics with higher repression scores reported less frequent and fewer symptoms than those with lower repression scores. RDS was not a determinant of self-rated seriousness.

The findings reveal that there was a gender difference in the experience of symptoms. Women reported a higher number of symptoms compared to men. In contrast, female asthmatics did not report more frequent symptoms or higher self-rated seriousness compared to male asthmatics, even though these relationships emerged at the bivariate level. Age, educational level, and marital status did not determine the seriousness measures.

The results show that including the product variables did not improve the determination of seriousness. All R2 change statistics were insignificant. This indicates that RDS does not moderate the relationships between seriousness and the determinants.

There were two general findings. First, average intensity over entire history was a more influential determinant of self-rated seriousness compared to average intensity over the last six months. Second, the relationships that emerged between the determinants and seriousness were in a positive direction.