Department of Nutrition, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, PO Box 1046, Blindern, 0317, Oslo, Norway.
Department of Chronic Diseases and Aging, Norwegian Institute of Public Health, PO Box 222, Skøyen, 0213, Oslo, Norway.
BMC Med Res Methodol. 2019 Jul 9;19(1):144. doi: 10.1186/s12874-019-0789-6.
Postal surveys are widely used in scientific studies, including dietary surveys, but few studies about methods to increase participation in national dietary surveys are published. In the present study we compared response rates in a pilot study to a national dietary survey among infants using two different incentives (gift certificate or lottery), personalization in the form of handwritten name and address vs. a printed label and mode of sending out invitations (e-mail or postal invitation).
In this parallel-design pseudo-randomized pilot trial, a nationally representative sample of 698 mothers of infants aged 6 and 12 months was drawn from the Norwegian National Registry and invited to complete a food frequency questionnaire about their infant's diet. One half of the mothers of 6 month olds were randomized by alternation to the lottery group (n = 198) and offered to participate in a lottery of two prizes (500 EUR and 1000 EUR). The other half (n = 200) was offered a gift certificate (50 EUR) upon completion of the questionnaire. Each incentive group was randomized by alternation to receiving an invitation with handwritten name and address or a printed label. For the mothers of infants aged 12 months (n = 300), 150 mothers received an e-mail invitation and 150 mothers received a postal invitation. Logistic regression was used for testing differences between the groups.
The response rate was significantly higher (p = 0.028) in the gift certificate group (72%) than in the lottery group (62%). No difference was seen between those receiving an invitation with a handwritten name and address (68%) compared to a printed label (66%, p = 0.72). A somewhat higher response rate was seen when using the postal (50%) compared to the e-mail invitation (43%, p = 0.25).
In this pseudo-randomized parallel-design trial of women participating in a national dietary survey among infants, the response rate was higher when offered a gift certificate than when participating in a lottery. Handwritten name and address did not affect participation compared to a printed label. Only a moderate difference was seen between the postal and e-mail invitation. Others conducting similar methodological studies are encouraged to publish their results to expand the knowledge basis in this area.
邮寄调查广泛应用于科学研究，包括饮食调查，但很少有关于提高全国饮食调查参与率的方法的研究发表。在本研究中，我们比较了使用两种不同激励措施（礼券或彩票）、手写姓名和地址与打印标签以及邀请方式（电子邮件或邮寄邀请）的个性化方案，在一项针对婴儿的全国饮食调查的试点研究和一项全国性研究中的应答率。
在这项平行设计的伪随机试点试验中，从挪威国家登记处抽取了一个具有代表性的 698 名 6 个月和 12 个月大婴儿的母亲样本，并邀请她们完成一份关于婴儿饮食的食物频率问卷。6 个月大婴儿的母亲中有一半通过交替被随机分配到彩票组（n=198），并获得参与两个奖项（500 欧元和 1000 欧元）的彩票的机会。另一半（n=200）在完成问卷后获得礼券（50 欧元）。每个激励组通过交替随机分配到手写姓名和地址的邀请或打印标签。对于 12 个月大婴儿的母亲（n=300），150 名母亲收到电子邮件邀请，150 名母亲收到邮寄邀请。逻辑回归用于检验组间差异。
礼券组（72%）的应答率显著高于彩票组（62%）（p=0.028）。收到手写姓名和地址的邀请（68%）与收到打印标签的邀请（66%）之间没有差异（p=0.72）。使用邮寄（50%）的应答率略高于电子邮件（43%）（p=0.25）。
在这项针对参与全国婴儿饮食调查的女性的伪随机平行设计试验中，与参与彩票相比，提供礼券会提高应答率。手写姓名和地址与打印标签相比，对参与没有影响。邮寄和电子邮件邀请之间只有适度差异。鼓励其他进行类似方法学研究的人发表他们的结果，以扩大该领域的知识基础。
