- Email: [email protected]
Participation in the first and second round of a mass-screening for colorectal cancer
Vol. 18. No. Printed in Great Britain
Sot. Sci. Med.
8, pp. 633-636,
1984
0277-9536184 93.00 + 0.00 Pergamon Press Ltd
PARTICIPATION IN THE FIRST AND SECOND ROUND OF A MASS-SCREENING FOR COLORECTAL CANCER Center for Social Science Research,
J. HARRY JANSEN* University of Leyden, Middelstegracht The Netherlands
4. 2312 TW Leyden,
Abstract-Using data from a survey of a sample of 239 people asked to participate in a community-based screening for colorectal cancer, factors associated with participation were identified. Central were variables about social participation and perceived threat of the disease. Of the variables that accounted for (non)participation in the first round only a few. such as perceived seriousness and active membership of clubs or associations, also accounted for participation in the second round of the screening. In conclusion it was argued that factors associated with participation in a first screening round cannot be used without adjustment to explain participation in a second round.
INTRODUCTION
Colorectal cancer is one of the most frequently occurring cancers in the Western world [I]. The survival-rates of colorectal cancer depend strongly on the stage of the disease at the time of diagnosis [2]. With the Hemoccult-test it is possible to identify blood in the feces. This can be a sign of colorectal cancer in an early stage. Because of its simplicity the test has been applied for population-based screening. Participants are instructed to collect a small specimen of feces from three bowel evacuations. These specimen have to be spread on a paper impregnated with guaiac. The test is positive if the collection paper turns blue after treatment with hydrogen peroxide (H202). The color change should be judged by an experienced examiner. In some countries this form of early detection is rather common (31. In The Netherlands a populationbased screening was organized in 1979 and 1980 [4]. As part of this program a sample of potential participants was asked in 1979 to indicate their reasons for (non)participation. In this report the results of this questionnaire are related to the participation in the two consecutive screening rounds in 1979 and in 1980. FACTORS THAT INFLUENCE PARTICIPATION
Research on factors related to participation in screening programs for colorectal cancer has been directed to special groups (such as hospital patients or women participating in a screening program for breast cancer) or has been performed only in situations where the screening is not repeated [5-81. Research on the participation in regular massscreening for breast- and cervix-cancer is more common [9, lo]. This research distinguishes itself from the other investigations because it attempts to examine factors related to participation in two consecutive screening-rounds. *The author wishes to thank associates of the former Institute of Social Oncology, in particular Richard B. Hayes, for their assistance.
This is important because the success of a screening program depends strongly upon a constant high participation. To attain a high participation, research results about reasons for participation found in the first round are often used. It is however not a matter of course that these results also apply for the second and next rounds. In the construction of the questionnaire, participation in a screening-program was seen as a form of preventive behavior as described by Kasl and Cobb [ 111. Two explanations for preventive behavior have been developed: one with an accent on socialpsychological variables [12-141 and one with the accent on social-cultural variables [15]. In this research both explanations are used with an emphasis on the social-psychological model. The ‘Health Belief Model’ [12] was central to our approach. The main variables in this model are the perceived seriousness of the disease, the perceived chance of getting the disease and the perceived benefits of the recommended preventive action. Further, the model includes some enabling and modifying factors like the costs of the preventive action, age, education, attitude to prevention in general and prior experience with the preventive action. The social-cultural-model is mainly based on the contrast between people that are parochially oriented and people that are more cosmopolite in orientation. This model has been operationalized by questions about the quantity, sort and intensity of social contacts. In summary four groups of variables were considered in the questionnaire: questions about the Hemoccult-test social and demographic variables variables from the ‘Health Belief Model’ social-cultural variables. METHODS
In 1979, an experimental screening for colorectal cancer was started in Zoetermeer, a fast growing Dutch city near The Hague. The experiment was initiated and carried out by a local general prac-
633
634
J. HARRY JANSEN Table I. Particioation
in 1980 bv aarticioation
Participation in 1979
Participation in 1980
N-total
in 1979 IN = 324) Participation 1979/1980
(58%) Yes
-I I2 (350,) both
(59%)
324
/19, 1132
(429’) 0 nol (10%) yes/
93 (29’“) one
(41O1) -I 19 (37”_) neither
titioner. After some publicity in the local newspaper and the distribution of posters; all the inhabitants born before 1939 were sent, by mail, a kit containing a leaflet with information about colorectal cancer and the purpose of the screening and material with instructions. People were asked to send back the materials after obtaining the specimen of feces from the next three bowel evacuations. The addresses were provided by the municipality continuous population registration system. This screening procedure was repeated in the same population in 1980 [4]. For this study, a random sample of 336 individuals was selected from the 15,261 potential participants in 1979. Of these 336 persons 324 were resident in the city at the time of the first and the second screening rounds, and, are subsequently considered as the study population. Each member of the study population was visited at home by a trained interviewer. The interviews took place during the time period when the first screening round was being carried out. The interview, which took about 20 minutes, was based upon a pre-coded instrument. Interviews were held with 239 (74%) persons, 12% refused to be interviewed and 14% were not at home after three visits or were for other reasons not available. Of the study population 59% participated in the screening program. In the same period the participation among all persons that were sent a Hemoccult-test was 58%. The interview campaign also had hardly any influence on the participation of the study population. RESULTS
Certain results are presented for the total sample (N = 324). Further results are presented for those that cooperated in the interviewing (N = 239). The total sumple
Table I shows participation in the two rounds of the screening for the total sample. For the entire Table 2. Participation
Sex Me” Women
N
Table 3. Participation Age in 1979 (YCdrS)
41-50 51-60 hl-7n ff; and older
N
132 I01 58 33
The interviewed
At the time of the interview, 139 respondents had taken a specimen from one or more stools. These respondents were asked about the specimen collection. There were little complaints about the test; only 2% thought the test was difficult and 12% said it was dirty to do. All the respondents were asked if they intend to participate in the next round, 86% said they would. Only half of the people that stated that they intend to participate in the next round really did so. All respondents who did not intend to participate or who did not know at that moment, did not participate in the second round. In the first round it was found that married people participated more than single people and that highly
m 1979 and 1980 by sex (N = 324)
Participation in 1979 (%) 56 62
161 163
sample the participation in the first round was 599; and in the second round 39”,/,.It should be noted that there are few people who became participants in the second round not having participated in the first round. This makes that turnover as a measure of change for subgroups gives little extra information, over simple differences in per cent decrease in participation. For both rounds women participated more than men although the differences are not significant (see Table 2). In 1979 the younger age-categories participated significantly more in the screening (x2 = 11.7, d.f. = 3, P < 0.01) this did not hold for the 1980 round (x2 = 7.1). The drop in participation was greatest in the group of oldest people (see Table 3). In 1979 there was a significant correlation between participation in the screening and response to the questionnaire (x2 = 35.4, d.f. = 1, P < O.OOl), this correlation did also hold for the second .round (x2 = 10.6, d.f. = 1, P < 0.01). Consequently the respondents participated more than the total sample, 69% in the first round and 44% in the second round. The decrease in participation for the non-respondents (26%) was less than for the respondents (36%).
Participation in 1980 0 1,;) 34 43
Decrease in participation C;) 40 31
in 1979 and 1980 per age-group (N = 324)
Participation I” 1979
Participation in 19X0
Decrease in pdrticipdtlo”
(‘3
C,,)
Cbl
65 62 52 39
42 43 36 18
36 32 30 54
Participation
in two rounds
of a screening
educated people also participated more. These were however not statistically significant differences (x2 = 3.1, d.f. = I and x2 = 3.8, d.f. = 3). Of the ‘Health Belief Model’ two variables had a significant correlation with participation. The first variable was the answer on the question ‘if you suffered from colorectal cancer, how serious would be the effects for your daily life’. Five answers were possible and ranged from ‘not serious’ to ‘very serious’. People participated more if they thought the effects of colorectal cancer were more serious (x2 = 12.0, d.f. = 4, P < 0.05); they also participated more if they expected that a regular test would raise .the chance of recovery (x2 = 11.7, d.f. = 1, P < 0.001). This variable was formulated by the question ‘do you think that a regular screening for blood in your feces gives you a better change on recovery from colorectal cancer’; yes or no. The third HBM-variable, the perceived chance of getting colorectal cancer, was a five point scale as answer on the question ‘how big a chance do you think you have to get colorectal cancer’. This variable did not correlate significant with participation in the screening. Although people that perceived to have a reasonable or high chance to get colorectal cancer participated more than people that perceived their chance was small. Only two of the variables that were used as an indicator for social participation in general, were significantly related with participation in the screening of 1979. People that answered positive on the question ‘are you an active member of a club or an association’ participated more in the screening (x2 = 5.0, d.f. = 1, P < 0.05). Although this could be an artifact of age, because older people are likely less often active members of sportsclubs, no such correlation was found with active membership of a political party or church. Nor did the quantity of association with other people influence participation in the screening. Important was association with different kinds of people (x2 = 12.1, d.f. = 3, P < 0.01). Respondents were asked to mention if they associate with people from one or more of these groups: family, neighbours, friends and colleagues. Two other variables were correlated with parTable 4. Participation
635
cancer
ticipation in the first round. If people know a colorectal patient the chance of participation is higher (x2= 8.2, d.f. = 1, P < 0.01). Further people participated more if they had talked about the test in the information-period just before the test was actually sent to them (XI= 20.3, d.f. = 1, P < 0.001). This may be a sign that people that are conscious of colorectal cancer are more likely to participate. Although it does not implicate that knowledge about the subject influences participation in the screening because participants and non-participants did not significantly differ in their knowledge about colorectal cancer and the screening. A nine-item scale covering subjects mentioned in the introductory leaflet was used for measuring knowledge. For the year 1980 most of the correlations found in 1979 between variables from the questionnaire and participation in the screening disappear. Table 4 shows the participation in the screening for the categories of the main variables of the Health Belief Model. In 1980, none of these was significantly correlated with participation. This may be the effect of the small sample that was interviewed. The pattern that was found in these variables in 1980 is the same, on a lower level, as in the 1979 data. Remarkable is the low participation of the group that perceived the effects of colorectal cancer as very serious. Because there is no correlation between perceived seriousness and perceived chance nor between those two variables and the perceived effects of the Hemoccult-test this low participation cannot be explained from the HBM itself. Only two variables that can be brought in connection with social participation do correlate with participation in the 1980 screening. These are ‘talked about the screening’ (x2 = 20.2, d.f. = 1, P < 0.001) and active in clubs and associations (x2 = 11.3, d.f. = 1, P < 0.01). Contrary to the first round there was also a significant correlation between active participation in a religious community and participation in the screening (x2 = 7.9, d.f. = 1, P < 0.01). There was no significant correlation with participation in the second round of the screening found for the social and demographic variables.
in 1979 and 1980 per category
N
for colorectal
Participation in 1919 Cm
of the HBM variables Participation in 1980 (0’) 1”
Decrease in participation (%)
seriousness of the effects of colorectal cancer Perceived
Not serious Less serious Serious More serious Very serious Perceived chance of getting colorectal cancer Hardly any change Small change Reasonable change Does the Hemocculttest raise chance of recovery Yes No Don’t know
18 48 80 33 53
56 58 79 82 60
33 44 45 52 41
44 19 36 42 34
115 89 24
64 72 79
39 45 54
38 38 32
210 IO 19
72 50 37
46 30 26
37 40 28
J. HARRY JANSEN
636 CONCLUSIONS
Studies that investigate volunteering behavior can suffer themselves from a lack of cooperation. If both forms of non-participation, also the (non) volunteering behavior studied and the noncooperation in the study are independent, this will do no harm. However, this is seldom the case. This report shows that volunteering in a screening for colorectal cancer is correlated with response to a questionnaire about that screening. It follows that participants in the screening are overrepresented in this study and also that the variation in variables we measured to explain participation in the screening is less than in the whole population. This practical insurmountable artifact may to some extent explain the weak results of this study. For the second round the correlations were weaker than those in the first round; only some aspects of social participation in general do correlate significantly with participation in both rounds of the screening. This shows that results of an investigation in the participation in the first round of a screening do not apply for the second
round without adjustment. It seems that variables central in the Health Belief Model as perceived seriousness of the disease and perceived chance on contracting the disease, do not anymore correlate significant with participation in the second round, although the pattern of association persists. This could be an indication that the HBM is useful for prediction participation in more than one round in a screening-program. Furthermore knowing a colorectal patient does only correlate with participation in the first round. It may be concluded that the first confrontation with the serious effects of colorectal cancer form a strong impulse to participation in the screening. If, over time, people grow familiar with colorectal cancer and its effects, this influence seems to decrease. This explains why only half of the people who intended to participate in the second round, actually participated a year later. On the other hand, these results show that certain factors are associated with participation. It would be a task for health educators to exploit this knowledge in designing
programs not only to initiate participation maintain levels of participation.
but also to
REFERENCES
1. Wynder E. L. and Reddy B. S. The epidemiology of cancer of the Large Bowel. Digestive Dis. 19, 937-946, 1974. 2. Laffall Jr and LaSalle D. Early diagnosis of colorectal cancer. CA-A Cam. J. Clin. 24, 2, 1974. 3. A.C.S. Developing a colorectal cancer education program. A.C.S. Inc., 1977. 4. Wolff A. N. de Een bevolkingsonderzoek naar colon- en rectum carcinoom met behulp van de Hemoccult-test (with a summary in English), Rotterdam, 1982. 5. Goodman M. J. Mass screening for colorectal cancer: a negative report. JAMA 237, 22, 1977. 6. Hastings J. B. Mass screening for colorectal cancer. Am. J. Surg. 127, 228-233, 1974. 7. Dent 0. and Goulston K. Socio-demographic correlates of intended acceptance of colorectal cancer screening; lecture to the Gastroenterologic Society of Australia, Brisbane, 1979. 8. Monroe H. S. ef al. Assessment of attitudes toward mass screening for colorectal cancer and polyps. Preu. Med. 10, 105-109 1981. 9. Heuvel W. J. A. van den. Participants and nonparticipants in a mammography mass-screening: who is who? In Breast Cancer ; Psycho -Social Aspects of Ear1.v Detection and Treatment (Edited by Brand P. C.). Lancaster, 1978. 10. Jansen J. H. and Hayes R. B. A prospective study of participation in a screening program for the detection of cervical cancer. U.I.C.C. Technical Report Series, 62, 43-51, 1981. Il. Kasl S. V. and Cobb S. Health behavior, illness behavior and sick role behavior. Archs enuir. Hlth 12, 246-267, 1966. 12. Rosenstock I. M. Historical origins of the health belief model. Hlth Educ. Monogr. 2, 328-335, 1977. 13. Antonovsky A. and Kats P. The model dental patient:
an empirical study of preventive health behaviour. Sot. Sci. Med. 4, 367-371, 1970. 14. Becker M. H. ec al. The health
belief model and prediction of dietary compliance: a field experiment. J.
Hlth sot. Behav. 18, 348-366, 1977. 15. Suchman F. Social patterns of illness and medical care. In Patients. Physicians and Illness (Edited by Jaco E. G.), pp. 262-279. Free Press, New York, 1972.
Sot. Sci. Med.
8, pp. 633-636,
1984
0277-9536184 93.00 + 0.00 Pergamon Press Ltd
PARTICIPATION IN THE FIRST AND SECOND ROUND OF A MASS-SCREENING FOR COLORECTAL CANCER Center for Social Science Research,
J. HARRY JANSEN* University of Leyden, Middelstegracht The Netherlands
4. 2312 TW Leyden,
Abstract-Using data from a survey of a sample of 239 people asked to participate in a community-based screening for colorectal cancer, factors associated with participation were identified. Central were variables about social participation and perceived threat of the disease. Of the variables that accounted for (non)participation in the first round only a few. such as perceived seriousness and active membership of clubs or associations, also accounted for participation in the second round of the screening. In conclusion it was argued that factors associated with participation in a first screening round cannot be used without adjustment to explain participation in a second round.
INTRODUCTION
Colorectal cancer is one of the most frequently occurring cancers in the Western world [I]. The survival-rates of colorectal cancer depend strongly on the stage of the disease at the time of diagnosis [2]. With the Hemoccult-test it is possible to identify blood in the feces. This can be a sign of colorectal cancer in an early stage. Because of its simplicity the test has been applied for population-based screening. Participants are instructed to collect a small specimen of feces from three bowel evacuations. These specimen have to be spread on a paper impregnated with guaiac. The test is positive if the collection paper turns blue after treatment with hydrogen peroxide (H202). The color change should be judged by an experienced examiner. In some countries this form of early detection is rather common (31. In The Netherlands a populationbased screening was organized in 1979 and 1980 [4]. As part of this program a sample of potential participants was asked in 1979 to indicate their reasons for (non)participation. In this report the results of this questionnaire are related to the participation in the two consecutive screening rounds in 1979 and in 1980. FACTORS THAT INFLUENCE PARTICIPATION
Research on factors related to participation in screening programs for colorectal cancer has been directed to special groups (such as hospital patients or women participating in a screening program for breast cancer) or has been performed only in situations where the screening is not repeated [5-81. Research on the participation in regular massscreening for breast- and cervix-cancer is more common [9, lo]. This research distinguishes itself from the other investigations because it attempts to examine factors related to participation in two consecutive screening-rounds. *The author wishes to thank associates of the former Institute of Social Oncology, in particular Richard B. Hayes, for their assistance.
This is important because the success of a screening program depends strongly upon a constant high participation. To attain a high participation, research results about reasons for participation found in the first round are often used. It is however not a matter of course that these results also apply for the second and next rounds. In the construction of the questionnaire, participation in a screening-program was seen as a form of preventive behavior as described by Kasl and Cobb [ 111. Two explanations for preventive behavior have been developed: one with an accent on socialpsychological variables [12-141 and one with the accent on social-cultural variables [15]. In this research both explanations are used with an emphasis on the social-psychological model. The ‘Health Belief Model’ [12] was central to our approach. The main variables in this model are the perceived seriousness of the disease, the perceived chance of getting the disease and the perceived benefits of the recommended preventive action. Further, the model includes some enabling and modifying factors like the costs of the preventive action, age, education, attitude to prevention in general and prior experience with the preventive action. The social-cultural-model is mainly based on the contrast between people that are parochially oriented and people that are more cosmopolite in orientation. This model has been operationalized by questions about the quantity, sort and intensity of social contacts. In summary four groups of variables were considered in the questionnaire: questions about the Hemoccult-test social and demographic variables variables from the ‘Health Belief Model’ social-cultural variables. METHODS
In 1979, an experimental screening for colorectal cancer was started in Zoetermeer, a fast growing Dutch city near The Hague. The experiment was initiated and carried out by a local general prac-
633
634
J. HARRY JANSEN Table I. Particioation
in 1980 bv aarticioation
Participation in 1979
Participation in 1980
N-total
in 1979 IN = 324) Participation 1979/1980
(58%) Yes
-I I2 (350,) both
(59%)
324
/19, 1132
(429’) 0 nol (10%) yes/
93 (29’“) one
(41O1) -I 19 (37”_) neither
titioner. After some publicity in the local newspaper and the distribution of posters; all the inhabitants born before 1939 were sent, by mail, a kit containing a leaflet with information about colorectal cancer and the purpose of the screening and material with instructions. People were asked to send back the materials after obtaining the specimen of feces from the next three bowel evacuations. The addresses were provided by the municipality continuous population registration system. This screening procedure was repeated in the same population in 1980 [4]. For this study, a random sample of 336 individuals was selected from the 15,261 potential participants in 1979. Of these 336 persons 324 were resident in the city at the time of the first and the second screening rounds, and, are subsequently considered as the study population. Each member of the study population was visited at home by a trained interviewer. The interviews took place during the time period when the first screening round was being carried out. The interview, which took about 20 minutes, was based upon a pre-coded instrument. Interviews were held with 239 (74%) persons, 12% refused to be interviewed and 14% were not at home after three visits or were for other reasons not available. Of the study population 59% participated in the screening program. In the same period the participation among all persons that were sent a Hemoccult-test was 58%. The interview campaign also had hardly any influence on the participation of the study population. RESULTS
Certain results are presented for the total sample (N = 324). Further results are presented for those that cooperated in the interviewing (N = 239). The total sumple
Table I shows participation in the two rounds of the screening for the total sample. For the entire Table 2. Participation
Sex Me” Women
N
Table 3. Participation Age in 1979 (YCdrS)
41-50 51-60 hl-7n ff; and older
N
132 I01 58 33
The interviewed
At the time of the interview, 139 respondents had taken a specimen from one or more stools. These respondents were asked about the specimen collection. There were little complaints about the test; only 2% thought the test was difficult and 12% said it was dirty to do. All the respondents were asked if they intend to participate in the next round, 86% said they would. Only half of the people that stated that they intend to participate in the next round really did so. All respondents who did not intend to participate or who did not know at that moment, did not participate in the second round. In the first round it was found that married people participated more than single people and that highly
m 1979 and 1980 by sex (N = 324)
Participation in 1979 (%) 56 62
161 163
sample the participation in the first round was 599; and in the second round 39”,/,.It should be noted that there are few people who became participants in the second round not having participated in the first round. This makes that turnover as a measure of change for subgroups gives little extra information, over simple differences in per cent decrease in participation. For both rounds women participated more than men although the differences are not significant (see Table 2). In 1979 the younger age-categories participated significantly more in the screening (x2 = 11.7, d.f. = 3, P < 0.01) this did not hold for the 1980 round (x2 = 7.1). The drop in participation was greatest in the group of oldest people (see Table 3). In 1979 there was a significant correlation between participation in the screening and response to the questionnaire (x2 = 35.4, d.f. = 1, P < O.OOl), this correlation did also hold for the second .round (x2 = 10.6, d.f. = 1, P < 0.01). Consequently the respondents participated more than the total sample, 69% in the first round and 44% in the second round. The decrease in participation for the non-respondents (26%) was less than for the respondents (36%).
Participation in 1980 0 1,;) 34 43
Decrease in participation C;) 40 31
in 1979 and 1980 per age-group (N = 324)
Participation I” 1979
Participation in 19X0
Decrease in pdrticipdtlo”
(‘3
C,,)
Cbl
65 62 52 39
42 43 36 18
36 32 30 54
Participation
in two rounds
of a screening
educated people also participated more. These were however not statistically significant differences (x2 = 3.1, d.f. = I and x2 = 3.8, d.f. = 3). Of the ‘Health Belief Model’ two variables had a significant correlation with participation. The first variable was the answer on the question ‘if you suffered from colorectal cancer, how serious would be the effects for your daily life’. Five answers were possible and ranged from ‘not serious’ to ‘very serious’. People participated more if they thought the effects of colorectal cancer were more serious (x2 = 12.0, d.f. = 4, P < 0.05); they also participated more if they expected that a regular test would raise .the chance of recovery (x2 = 11.7, d.f. = 1, P < 0.001). This variable was formulated by the question ‘do you think that a regular screening for blood in your feces gives you a better change on recovery from colorectal cancer’; yes or no. The third HBM-variable, the perceived chance of getting colorectal cancer, was a five point scale as answer on the question ‘how big a chance do you think you have to get colorectal cancer’. This variable did not correlate significant with participation in the screening. Although people that perceived to have a reasonable or high chance to get colorectal cancer participated more than people that perceived their chance was small. Only two of the variables that were used as an indicator for social participation in general, were significantly related with participation in the screening of 1979. People that answered positive on the question ‘are you an active member of a club or an association’ participated more in the screening (x2 = 5.0, d.f. = 1, P < 0.05). Although this could be an artifact of age, because older people are likely less often active members of sportsclubs, no such correlation was found with active membership of a political party or church. Nor did the quantity of association with other people influence participation in the screening. Important was association with different kinds of people (x2 = 12.1, d.f. = 3, P < 0.01). Respondents were asked to mention if they associate with people from one or more of these groups: family, neighbours, friends and colleagues. Two other variables were correlated with parTable 4. Participation
635
cancer
ticipation in the first round. If people know a colorectal patient the chance of participation is higher (x2= 8.2, d.f. = 1, P < 0.01). Further people participated more if they had talked about the test in the information-period just before the test was actually sent to them (XI= 20.3, d.f. = 1, P < 0.001). This may be a sign that people that are conscious of colorectal cancer are more likely to participate. Although it does not implicate that knowledge about the subject influences participation in the screening because participants and non-participants did not significantly differ in their knowledge about colorectal cancer and the screening. A nine-item scale covering subjects mentioned in the introductory leaflet was used for measuring knowledge. For the year 1980 most of the correlations found in 1979 between variables from the questionnaire and participation in the screening disappear. Table 4 shows the participation in the screening for the categories of the main variables of the Health Belief Model. In 1980, none of these was significantly correlated with participation. This may be the effect of the small sample that was interviewed. The pattern that was found in these variables in 1980 is the same, on a lower level, as in the 1979 data. Remarkable is the low participation of the group that perceived the effects of colorectal cancer as very serious. Because there is no correlation between perceived seriousness and perceived chance nor between those two variables and the perceived effects of the Hemoccult-test this low participation cannot be explained from the HBM itself. Only two variables that can be brought in connection with social participation do correlate with participation in the 1980 screening. These are ‘talked about the screening’ (x2 = 20.2, d.f. = 1, P < 0.001) and active in clubs and associations (x2 = 11.3, d.f. = 1, P < 0.01). Contrary to the first round there was also a significant correlation between active participation in a religious community and participation in the screening (x2 = 7.9, d.f. = 1, P < 0.01). There was no significant correlation with participation in the second round of the screening found for the social and demographic variables.
in 1979 and 1980 per category
N
for colorectal
Participation in 1919 Cm
of the HBM variables Participation in 1980 (0’) 1”
Decrease in participation (%)
seriousness of the effects of colorectal cancer Perceived
Not serious Less serious Serious More serious Very serious Perceived chance of getting colorectal cancer Hardly any change Small change Reasonable change Does the Hemocculttest raise chance of recovery Yes No Don’t know
18 48 80 33 53
56 58 79 82 60
33 44 45 52 41
44 19 36 42 34
115 89 24
64 72 79
39 45 54
38 38 32
210 IO 19
72 50 37
46 30 26
37 40 28
J. HARRY JANSEN
636 CONCLUSIONS
Studies that investigate volunteering behavior can suffer themselves from a lack of cooperation. If both forms of non-participation, also the (non) volunteering behavior studied and the noncooperation in the study are independent, this will do no harm. However, this is seldom the case. This report shows that volunteering in a screening for colorectal cancer is correlated with response to a questionnaire about that screening. It follows that participants in the screening are overrepresented in this study and also that the variation in variables we measured to explain participation in the screening is less than in the whole population. This practical insurmountable artifact may to some extent explain the weak results of this study. For the second round the correlations were weaker than those in the first round; only some aspects of social participation in general do correlate significantly with participation in both rounds of the screening. This shows that results of an investigation in the participation in the first round of a screening do not apply for the second
round without adjustment. It seems that variables central in the Health Belief Model as perceived seriousness of the disease and perceived chance on contracting the disease, do not anymore correlate significant with participation in the second round, although the pattern of association persists. This could be an indication that the HBM is useful for prediction participation in more than one round in a screening-program. Furthermore knowing a colorectal patient does only correlate with participation in the first round. It may be concluded that the first confrontation with the serious effects of colorectal cancer form a strong impulse to participation in the screening. If, over time, people grow familiar with colorectal cancer and its effects, this influence seems to decrease. This explains why only half of the people who intended to participate in the second round, actually participated a year later. On the other hand, these results show that certain factors are associated with participation. It would be a task for health educators to exploit this knowledge in designing
programs not only to initiate participation maintain levels of participation.
but also to
REFERENCES
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