Study selection
The PRISMA flow diagram (22) was used to record the results of the study selection (Figure 1). The electronic database search identified 2,090 records for screening. The reference lists of the final included studies, as well as of the similar systematic reviews on gender (11) and ethnic minorities (12), uncovered a further 28 potentially relevant papers. After duplicates were removed, 1,782 studies remained for the title and abstract screen. Of these, 1,687 studies were excluded, as they didn’t meet the inclusion criteria, leaving 95 articles for a full text screen to be assessed for eligibility. A further 75 articles were excluded at this stage. There were 20 primary studies that met the inclusion criteria for the review.
Characteristics of included studies
Characteristics of included studies are displayed in Additional File 2. The 20 included studies (6-8, 16-19, 29-41) were all written between the years 2001 to 2015. Of the 20 studies, four (7, 29-31) were from Spain, two (16, 32) were from Italy and two (33, 34) from Croatia. One study (6) was from both the Republic of Ireland & Northern Ireland. Another study (35) included nine European countries: Austria, France, Germany, Italy, the Netherlands, Poland, Russia, Spain and the UK. The remaining studies included one from each of the following countries: Turkey (36), Israel (37), Portugal (18), Germany (8), France (38), Switzerland (17), Sweden (39), Northern Ireland (40), Denmark (19) and Estonia (41).
All 20 studies (6-8, 16-19, 29-41) were cross-sectional studies. Their methods included telephone interviews (16, 29, 31, 39), questionnaires (7, 8, 18, 19, 32-34, 37, 38, 40, 41) and face-to-face interviews (6, 17, 30, 35, 36). One article (37) appeared to be a cross-sectional study, however, it seemed to take a longer period to collect data (more than four years).
The overall number of respondents across all 20 studies was 67,309. The number of respondents in the studies ranged from 212 respondents (34) to 28,090 respondents (8). Participant selection was reported to be random for all studies except one which was snowball (i.e. non-random) (37), one which used consecutive patients (32) and one which was unclear (18). The sampling strategy for six (7, 17, 33, 34, 38, 41) of the random sampling studies was not clearly reported. The majority of the studies only questioned adults. However, four of them (7, 17, 35, 41) included both adults and children. All studies included both genders; with all except one study (39) having a higher proportion of females.
Socioeconomic position type and stroke knowledge assessment
Table 3 displays the studies’ characteristics with regards to the aspect of socioeconomic position that results were given by, type of questioning and stroke knowledge. All studies gave results by educational level as a measure of SEP, except one (31) that gave professional status only. Aside from education, two studies also gave results by income (30, 37), one also by both income and professional status (36) and one (40) also by deprivation level.
The measures of knowledge of stroke risk factors and warning signs was varied, ranging from open to closed-ended questions. With regards to how studies displayed their type of questioning by SEP, there were 12 studies (6, 7, 16-19, 29, 33-35, 40, 41) that asked closed-ended questions; i.e. the participant was given a list of stroke warning signs and/or risk factors and they were asked to select which ones were correct. This tested their recognition. Seven of the studies (8, 30, 32, 36-39), with regards to SEP, asked open-ended questions, where the participants would be asked to name as many stroke warning signs and/or risk factors as they could. This tested recall. One study (31), with regards to SEP, included a combination of both open and closed-ended questions.
Of the 20 studies, 16 of them (6, 7, 16-19, 30-34, 36, 38-41) included both knowledge of risk factors and warning signs of stroke. One study (8) looked only at risk factors and three (29, 35, 37) looked only at warning signs.
Table 3: Stroke knowledge assessment by aspect of socioeconomic position in WHO European region countries
First author (Date) Country
|
Socioeconomic position aspect
|
Open or closed-ended questions (when results were broken down by SEP)?
|
Knowledge of stroke risk factors?
|
Knowledge of stroke warning signs?
|
Baldereschi(16) (2015) Italy
|
Education
|
Closed
|
Y
|
Y
|
Dominicis(32) (2006) Italy
|
Education
|
Open
|
Y
|
Y
|
Evci(36) (2007) Turkey
|
Education
Income
Professional status
|
Open
|
Y
|
Y
|
Hickey(6) (2009) Republic of Ireland & Northern Ireland
|
Education
|
Closed
|
Y
|
Y
|
Lundelin(29) (2012) Spain
|
Education
|
Closed
|
N
|
Y
|
Mata(35) (2012) Austria, France, Germany, Italy, the Netherlands, Poland, Russia, Spain and UK
|
Education
|
Closed
|
N
|
Y
|
Melnikov(37) (2016) Israel
|
Education
Income
|
Open
|
N
|
Y
|
Montaner(7) (2001) Spain
|
Education
|
Closed
|
Y
|
Y
|
Moreira(18) (2011) Portugal
|
Education
|
Closed
|
Y
|
Y
|
Müller‑Nordhorn(8) (2006) Germany
|
Education
|
Open
|
Y
|
N
|
Neau(38) (2009) France
|
Education
|
Open
|
Y
|
Y
|
Nedeltchev(17) (2007) Switzerland
|
Education
|
Closed
|
Y
|
Y
|
Nordanstig(39) (2014) Sweden
|
Education
|
Open
|
Y
|
Y
|
Parahoo(40) (2003) Northern Ireland
|
Education
Deprivation
|
Closed
|
Y
|
Y
|
Ramirez-Moreno(30) (2015) Spain
|
Education
Income
|
Open
|
Y
|
Y
|
Segura(31) (2003) Spain
|
Professional status
|
Both
|
Y
|
Y
|
Truelsen(19) (2010) Denmark
|
Education
|
Closed
|
Y
|
Y
|
Vibo(41) (2013) Estonia
|
Education
|
Closed
|
Y
|
Y
|
Vukovic(33) (2009) Croatia
|
Education
|
Closed
|
Y
|
Y
|
Vuletić(34) (2006) Croatia
|
Education
|
Closed
|
Y
|
Y
|
Y = yes; N = no
Risk of bias within studies
Assessment of the quality of the included studies is displayed in Additional File 3, using the AXIS tool for cross-sectional studies (28). Using this tool, the authors found that the studies were of mixed quality and varied in sampling and response bias.
Only five studies (7, 8, 16, 18, 31) clearly justified their sample size. There were 13 studies (6, 8, 16, 18, 29-33, 35, 36, 39, 40) whose sample frame was taken from an appropriate population base so that it closely represented the target/reference population under investigation. A slightly different set of 13 studies (6, 8, 16, 17, 19, 29-33, 35, 36, 40) used selection processes that were likely to select subjects/participants that were representative of the target/reference population under investigation. Two studies (32, 39) undertook measures to address and categorise non-responders if response rate was low. In all 20 studies (6-8, 16-19, 29-41), the risk factor and outcome variables measured were appropriate to the aims of the study, however only half of the papers (6-8, 17, 18, 30, 35-37, 40) had used measurements/instruments that had been previously trialled, piloted or published. All studies, except three (31, 38, 40), were clear about what was used to determine statistical significance and/or precision estimates. All 20 studies (6-8, 16-19, 29-41) described their methods in sufficient detail to enable them to be repeated.
Basic data were adequately described in the results of all 20 studies (6-8, 16-19, 29-41). However, in at least nine studies (6, 8, 16, 19, 29-31, 39, 40), the response rate raised concerns about non-response bias. Only one study (38), out of those in which it was relevant, described information about non-response bias. In two studies (32, 36) this was not applicable as the response rate was high. Results were internally consistent for all except three studies (7, 29, 31). In all 20 studies (6-8, 16-19, 29-41), the results for the analyses described in the methods were presented, and the authors’ discussions and conclusions were justified by the results. Limitations of studies were discussed in all except two studies (36, 40). No funding sources or conflicts of interest that may have affected the authors’ interpretation of the results were apparent in any of the studies, however in seven studies (7, 31, 33, 34, 38, 40, 41), no information was provided with regards to this. In 11 studies (6, 8, 16, 29, 30, 32, 35-38, 41), ethical approval or consent of participants was attained and in the remaining studies it was unclear.
Results of individual studies
The most commonly recognised risk factors for stroke across the studies were hypertension, high cholesterol, obesity and smoking (see Additional File 4). Out of eight studies (8, 30-32, 36-39) that asked open questions with regards to risk factors and gave a percentage of the number of people able to give at least one correct risk factor of stroke, the results ranged from 50.8% (32) to 89.5% (38).
The most commonly recognised warning signs of stroke across the studies were weakness of one side of body, speech problems and headache. Out of the eight studies (7, 30-32, 36-39) that asked open questions with regards to stroke warning signs and gave a percentage of the number of people able to give at least one correct warning sign of stroke, the results ranged from 32.6% (31) to 89.1% (37). Five of these studies (7, 30, 36, 37, 39) gave results over 50%; meaning that over half of participants in these studies were able to correctly identify a warning sign of stroke without being prompted. The other three studies (31, 32, 38) gave results of less than 50%. Out of the five studies (16, 18, 19, 34, 35) that asked closed questions with regards to stroke warning signs and gave a percentage of the number of people able to correctly identify at least one warning sign from a list, the results ranged from 68.7% (16) to 98% (19).
Knowledge of stroke risk factors by SEP
Out of the 17 studies (6-8, 16-19, 30-34, 36, 38-41) that assessed knowledge of risk factors for stroke, 11 of them (8, 16, 17, 30-32, 34, 36, 39-41) found there to be better knowledge with a higher SEP (Table 4). With reference to Table 3, all of these studies looked at education except for one article (31), which looked only at professional status, and found that ‘home-based occupations’ (such as housewives, pensioners, unemployed and disabled people) were linked to a lower knowledge of stroke risk factors in comparison with ‘non home-based occupations’ (which included all other occupations). Two of the studies (30, 36), which found this positive association between SEP and risk factor knowledge, also looked at income, and one of these (36) also found this association with professional status.
The authors of one study (7) had disaggregated their results by different risk factors, and found there to be better knowledge of one risk factor (arrhythmia) with higher SEP (p<0.05). However, this same study found no difference with regards to SEP for the other five risk factors (hypertension, diabetes, smoking, alcohol, coronary heart disease (CHD)) (7).
Four studies (6, 19, 33, 38) found there to be no difference in knowledge of stroke risk factors by SEP. For all of these, the measure of SEP was education. Amongst these was one article (33) which found that there was no overall difference, however it found that people with a lower SEP were less likely to name physical inactivity as a risk factor.
Only the authors of one study (18), which had a sample size of 663 respondents, found that there was a higher knowledge of risk factors with a lower SEP; they found that less educated people more frequently recognised stroke risk factors. This was, however, only with regards to vascular risk factors.
Knowledge of stroke warning signs by SEP
Out of the 19 studies (6, 7, 16-19, 29-41) that assessed knowledge of stroke warning signs, 15 studies (6, 7, 16, 17, 29-37, 39, 41) found there to be better knowledge of stroke warning signs with a higher SEP (Table 4). With reference to Table 3, all of these articles looked at education, except one (31) which only looked at professional status and found that, similarly as it did for risk factors, ‘home-based occupations’ were associated with a lower knowledge of stroke warning signs. Three of these studies (30, 36, 37) also found this positive association with regards to higher income, and one study (36), found this positive association with regards to professional status. One study (35), which looked at educational level in nine countries, found this positive trend across all countries, however the knowledge level was rather varied between countries. They found that the populations of Austria and Germany were the most knowledgeable, followed by the UK, whilst the populations of Spain and Italy were the least aware of stroke warning signs.
Three studies (19, 38, 40) found there to be no difference in knowledge of warning signs by SEP. One study (18), as it had done for risk factors, found that there was a higher knowledge of warning signs with a lower SEP.
Similarities and differences between knowledge of risk factors and warning signs by SEP amongst studies
Out of the 16 studies (6, 7, 16-19, 30-34, 36, 38-41) that included both knowledge of risk factors and warning signs, 12 of them (16-19, 30-32, 34, 36, 38, 39, 41) had similar associations with regards to knowledge of both these factors and SEP. For example, if they found higher SEP to mean better knowledge, they found this for both risk factors and for warning signs. One study (7), as mentioned earlier, found there to be increasing knowledge of warning signs with a higher SEP, but with regards to risk factors there was no difference in knowledge by SEP, except that people of a higher SEP correctly answered arrhythmia as a risk factor.
Two studies (6, 33) found that there was no difference in knowledge of stroke risk factors and level of SEP but that there was a better knowledge of stroke warning signs in higher SEP. One study (40), found the opposite, in that people with a higher SEP had more knowledge of stroke risk factors (p<0.001), but there was no difference in knowledge of warning signs by SEP.
Most of the studies in Spain (29-31, 35) and Italy (16, 32, 35) had similar outcomes in that, where risk factors and warning signs were looked at, increasing knowledge was always positively correlated with a higher SEP. The only exception was a Spanish study which found no difference by SEP with regards to risk factors, except for arrhythmia where it was positively correlated with a higher SEP (7).
The two studies undertaken in Croatia (33, 34) did not have the same correlations with regards to risk factors, but did for warning signs. The studies undertaken in Northern Ireland (6, 40) did not share similar correlations with regards to either risk factors or warning signs, however one of these studies (6) also included the Republic of Ireland and did not distinguish between the two countries with regards to stroke knowledge and its association with SEP. Another study (35) included the UK, amongst other countries, but did not break its results down to show Northern Ireland.
Details of the results of individual studies by SEP are displayed in Additional File 5. Please see this supplementary file for a breakdown of the quantitative results of the individual studies.
Table 4: Results of individual studies by socioeconomic position
First author (Date) Country
|
Risk factors
|
Warning signs
|
No statistically significant differences by SEP?
|
Statistically better knowledge in higher SEP?
|
Statistically better knowledge in lower SEP?
|
No statistically significant differences by SEP?
|
Statistically better knowledge in higher SEP?
|
Statistically better knowledge in lower SEP?
|
Baldereschi(16) (2015) Italy
|
|
√
|
|
|
√
|
|
Dominicis(32) (2006) Italy
|
|
√*
|
|
|
√*
|
|
Evci(36) (2007) Turkey
|
|
√
|
|
|
√
|
|
Hickey(6) (2009) Republic of Ireland & Northern Ireland
|
√
|
|
|
|
√
|
|
Lundelin(29) (2012) Spain
|
N/A
|
|
√
|
|
Mata(35) (2014) Austria, France, Germany, Italy, the Netherlands, Poland, Russia, Spain and UK
|
N/A
|
|
√*
|
|
Melnikov(37) (2016) Israel
|
N/A
|
|
√
|
|
Montaner(7) (2001) Spain
|
√
(for all except arrhythmia)
|
√
(for arrhythmia)
|
|
|
√
|
|
Moreira(18) (2011) Portugal
|
|
|
√*
|
|
|
√*
|
Müller‑Nordhorn(8) (2006) Germany
|
|
√
|
|
N/A
|
Neau(38) (2009) France
|
√
|
|
|
√
|
|
|
Nedeltchev(17) (2007) Switzerland
|
|
√
|
|
|
√*
|
|
Nordanstig(39) (2014) Sweden
|
|
√
|
|
|
√
|
|
Parahoo(40) (2003) Northern Ireland
|
|
√
|
|
√
|
|
|
Ramirez-Moreno(30) (2015) Spain
|
|
√
|
|
|
√
|
|
Segura(31) (2003) Spain
|
|
√
|
|
|
√
|
|
Truelsen(19) (2010) Denmark
|
√
|
|
|
√
|
|
|
Vibo(41) (2013) Estonia
|
|
√
|
|
|
√
|
|
Vukovic(33) (2009) Croatia
|
√
|
|
|
|
√
|
|
Vuletić(34) (2006) Croatia
|
|
√
|
|
|
√
|
|
√ = result of the individual study.
* = Authors of the individual study reported this result, albeit statistics were not reported. This may be because associations with SEP were not the primary purpose of their study. However, as they reported specific patterns in their results and have reported associations with SEP, the authors of this systematic review have acknowledged these. Please see Additional File 5 for a full quantitative breakdown of results.
N/A = not applicable as the study did not look at this aspect. Where cells are empty, this was not a result of the individual study.
Risk of bias in relation to study results
Although the critical appraisal tool AXIS (28) does not provide a numerical scale for assessing study quality, some studies were found to have answered positively to more questions than others (8, 16, 32, 36) and therefore were of a higher quality. These studies all gave the results of better stroke knowledge with increasing SEP.
Four (31, 34, 37, 41) of the five studies (31, 34, 37, 40, 41), which had the majority of negative or unclear responses using the AXIS tool, and were therefore of a lower quality, found there to be better stroke knowledge with increasing SEP. However, one of these studies (40) found no difference in knowledge of warning signs by SEP.
The other articles that gave results where higher SEP was not necessarily associated with increasing knowledge of stroke (7, 18, 19, 33, 38) had fewer positive responses in the AXIS tool, and therefore were of a lower quality, except for one (6) which had a higher number of positive responses and was therefore of a higher quality.