We observed that a greater proportion of men declined participation in the baseline GOS recruitment compared to women. For men, the most common reasons for non-participation, in descending order were: (i) personal reason/disinterest, (ii) time constraints and (iii) frailty/inability to cope with the study requirements. For women, the most common reasons for non-participation in descending order were: (i) personal reason/disinterest, (ii) frailty/inability to cope with the study, (iii) time constraints, and (iv) reluctance over medical testing. Men were more likely to decline participation due to time constraints than women. Women were more likely to decline due to reasons associated with frailty and due to reluctance over medical testing, compared to men.
Our observation that men had an increased propensity to decline participation compared to women, is consistent with other studies[6, 7]. Interestingly, we observed no sex-difference in the level of disinterest; furthermore, we can confirm that disinterest was not borne out of religious/philosophical objections, family interference, privacy concerns, or a fear of uncovering a medical problem (subgroups that were collapsed to form the personal reason/disinterest group). However, evidence exists to suggest that people who experience symptoms relevant to the health conditions under investigation are more likely to take part in studies than those who do not have those symptoms[1, 8]. Given that osteoporosis often remains undetected until after a fragility fracture occurs[9], it is plausible that non-participation related to disinterest may be due to a lack of awareness of the disease. Osteoporosis has also been identified as a condition with ‘low salience’ among the lay and medical communities – there exists a level of ambivalence and unconcern about osteoporosis in individual patients and the general population[10, 11]. Other factors that hampered interest may have been that certain attributes of the study were not salient or appealing enough to provide motivation to participate[12]; people may not see a personal gain from participating or feel disillusioned with scientific research on the whole[13]. Thus, highlighting personal relevance during the recruitment phase of a study may help combat antipathy towards research participation.
Women were more likely than men to decline participation due to frailty, or the inability to cope with requirements of the GOS study. The recruitment of elderly individuals to epidemiological studies has obvious difficulties[14, 15]. A number of published studies that examined frailty-related reasons for non-participation suggested that women may be impeded by personal illness more so than men[16].
Compared to men, we also observed women to be more likely to decline participation due to reluctance over medical testing. A 2007 study reported that women may have a stronger perception of risks and harms involved with epidemiological research compared to men[17]. This suggestion offers a plausible explanation for our observations, especially given that participation in the GOS required a number of clinical examinations. Furthermore, reluctance was not due to an avoidance of confronting medical issues, but rather due to concerns about possible stress and adverse effects of the battery of clinical examinations proposed.
The final key reason for non-participation was related to time constraints, whereby men were more likely to report limited time compared to women. To minimise problems associated with availability due to work commitments, the GOS offered potential participants appointment times after hours and at weekends. Time constraints have consistently been reported by other studies as a barrier to participation[6, 18].
This study has some notable strengths. First, the GOS re-contacted non-responders, whereby those who did not respond to the initial invitation were followed-up. A problem that is common to studies where mail surveys are utilised is that often there is no attempt made to ascertain whether non-response was due to the letter not being received, or because individuals have consciously chosen not to participate[18, 19]. Second, the GOS did not employ ambiguous categories to define reasons for non-participation, but rather explored precise reasons to improve clarity. This study also has some limitations. We are unable to comment on age-related reasons for non-participation, due to these data being unavailable. Furthermore, the female and male cohorts of the GOS were recruited 10 years apart, so the observed sex-differences in reasons may reflect a period effect, whereby the consequences of influences may vary with time.
