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Open Access 01-12-2015 | Study protocol

Design and baseline characteristics of the PerfectFit study: a multicenter cluster-randomized trial of a lifestyle intervention in employees with increased cardiovascular risk

Authors: Tessa A. Kouwenhoven-Pasmooij, Bosiljka Djikanovic, Suzan J. W. Robroek, Pieter Helmhout, Alex Burdorf, M. G. Myriam Hunink

Published in: BMC Public Health | Issue 1/2015

Abstract

Background

The prevalence of unhealthy lifestyles and preventable chronic diseases is high. They lead to disabilities and sickness absence, which might be reduced if health promotion measures were applied. Therefore, we developed the PerfectFit health promotion intervention with a “blended care”-approach, which consists of a web-based health risk assessment (HRA) including tailored and personalized advice, followed by motivational interviewing (MI). We hypothesize that adding MI to a web-based HRA leads to better health outcomes. The objective is to describe the design and baseline characteristics of the PerfectFit study, which is being conducted among employees with high cardiovascular risk in the military workforce, the police organization and an academic hospital.

Methods

PerfectFit is a cluster randomized controlled trial, consisting of two arms. Based on cardiovascular risk profiling, done between 2012 and 2014, we included employees based on one or more risk factors and motivation to participate. One arm is the ‘limited’ health program (control) that consists of: (a) an HRA as a decision aid for lifestyle changes, including tailored and personalized advice, and pros and cons of the options, and (b) a newsletter every 3 months. The other arm is the ‘extensive’ program (intervention), which is additionally offered MI-sessions by trained occupational physicians, 4 face-to-face and 3 by telephone, and is offered more choices of health promotion activities in the HRA. During the follow-up period, participants choose the health promotion activities they personally prefer. After six and twelve months, outcomes will be assessed by online questionnaires. After twelve months the cardiovascular risk profiling will be repeated. The primary outcome is self-reported general health. Secondary outcomes are self-reported work ability, CVD-risk score, sickness absence, productivity loss at work, participation in health promotion activities, changes in lifestyle (smoking, alcohol consumption, physical activity, stress management) and body mass index. Furthermore, a process evaluation and an economic analysis will be performed.

Discussion

Additional coaching using MI is expected to be a key factor for success of the web-based HRA in employees with increased cardiovascular risk. This “blended care”-approach may be an essential strategy for effective health promotion activities.

Trial registration

Dutch Trial Register by registration number NTR4894, 14/11/2014.

Ng M, Fleming T, Robinson M, Thomson B, Graetz N, Margono C, et al. Global, regional, and national prevalence of overweight and obesity in children and adults during 1980–2013: a systematic analysis for the Global Burden of Disease Study. Lancet. 2013;384(9945):766–81.CrossRef

Collaborators GMaCoD. Global, regional, and national age–sex specific all-cause and cause-specific mortality for 240 causes of death, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet. 2015;385(9963):117–71.CrossRef

WHO. Global status report on noncommunicable diseases 2010. Geneva, Switzerland: World Health Organization; 2011.

Abegunde D, Stanciole A. An estimation of the economic impact of chronic noncommunicable diseases in selected countries. Geneva, Switzerland: World Health Organization. Department of Chronic Diseases and Health Promotion; 2006.

Suhrcke M, Nugent RA, Stuckler D, Rocco L. Chronic Disease: An Economic Perspective. London: Oxford Health Alliance; 2006.

Centers for Disease Control and Prevention (CDC). The Costs of Chronic Diseases and Health Risk Behaviors. http://www.cdc.gov/chronicdisease/overview/#sec3. Accessed 9 May 2015.

Wantland JD, Portillo JC, Holzemer LW, Slaughter R, McGhee ME. The Effectiveness of Web-Based vs. Non-Web-Based Interventions: A Meta-Analysis of Behavioral Change Outcomes. J Med Internet Res. 2004;6(4):e40.CrossRefPubMedPubMedCentral

Neve M, Morgan PJ, Jones PR, Collins CE. Effectiveness of web-based interventions in achieving weight loss and weight loss maintenance in overweight and obese adults: a systematic review with meta-analysis. Obes Rev. 2010;11(4):306–21.CrossRefPubMed

Colkesen E, Niessen M, Peek N, Vosbergen S, Kraaijenhagen R, van Kalken C, et al. Initiation of health-behaviour change among employees participating in a web-based health risk assessment with tailored feedback. J Occup Med Toxicology. 2011;6(1):5.CrossRef

10.

Conn VS, Hafdahl AR, Cooper PS, Brown LM, Lusk SL. Meta-Analysis of Workplace Physical Activity Interventions. Am J Prev Med. 2009;37(4):330–9.CrossRefPubMedPubMedCentral

11.

Pelletier KR. A Review and Analysis of the Clinical and Cost-Effectiveness Studies of Comprehensive Health Promotion and Disease Management Programs at the Worksite: Update VII 2004–2008. J Occup Environ Med. 2009;51(7):822–37.CrossRefPubMed

12.

Soler RE, Leeks KD, Razi S, Hopkins DP, Griffith M, Aten A, et al. A Systematic Review of Selected Interventions for Worksite Health Promotion: The Assessment of Health Risks with Feedback. Am J Prev Med. 2010;38(2, Supplement):S237–62.CrossRefPubMed

13.

Goetzel RZ, Ozminkowski RJ. The Health and Cost Benefits of Work Site Health-Promotion Programs. Annu Rev Public Health. 2008;29(1):303–23.CrossRefPubMed

14.

Project prevention pays for everyone : return on investment in a healthier lifestyle (fig. ill.). Amsterdam: PricewaterhouseCoopers. 2010. http://beheer.nisb.nl/cogito/modules/uploads/docs/59231288960002.pdf. Accessed May 2015.

15.

Krebs P, Prochaska JO, Rossi JS. A meta-analysis of computer-tailored interventions for health behavior change. Prev Med. 2010;51(3–4):214–21.CrossRefPubMedPubMedCentral

16.

Britt E, Hudson SM, Blampied NM. Motivational interviewing in health settings: a review. Patient Educ Couns. 2004;53(2):147–55.CrossRefPubMed

17.

Brug J, Spikmans F, Aartsen C, Breedveld B, Bes R, Fereira I. Training dietitians in basic motivational interviewing skills results in changes in their counseling style and in lower saturated fat intakes in their patients. J Nutr Educ Behav. 2007;39:8–12.CrossRefPubMed

18.

Edwards EJ, Stapleton P, Williams K, Ball L. Building skills, knowledge and confidence in eating and exercise behavior change: Brief motivational interviewing training for healthcare providers. Patient Educ Couns. 2015;98(5):674-76.

19.

Lane C, Huws-Thomas M, Hood K, Rollnick S, Edwards K, Robling M. Measuring adaptations of motivational interviewing: the development and validation of the behavior change counseling index (BECCI). Patient Educ Couns. 2005;56:166–73.CrossRefPubMed

20.

Resnicow K, Jackson A, Wang T, De AK, McCarty F, Dudley WN. A motivational interviewing intervention to increase fruit and vegetable intake through Black churches: results of the Eat for Life trial. Am J Public Health. 2001;91:1686–93.CrossRefPubMedPubMedCentral

21.

Rollnick S, Allison J, Ballasiotes S, Barth T, Butler C, Rose G. Variations on a theme: motivational interviewing and its adaptions. Motivational interviewing: preparing people for change 2002:251–269.

22.

van Keulen H, Mesters I, Brug J, Ausems M, Campbell M, Resnicow K, et al. Vitalum study design: RCT evaluating the efficacy of tailored print communication and telephone motivational interviewing on multiple health behaviors. BMC Public Health. 2008;8(1):216.CrossRefPubMedPubMedCentral

23.

Groeneveld I, Proper K, van der Beek A, Hildebrandt V, van Mechelen W. Short and long term effects of a lifestyle intervention for construction workers at risk for cardiovascular disease: a randomized controlled trial. BMC Public Health. 2011;11(1):836.CrossRefPubMedPubMedCentral

24.

Miller WR, Rollnick S. Motivational interviewing: preparing people for change. 2nd ed. London: Guilford Press; 2002.

25.

Riper H, van Ballegooijen W, Kooistra L, de Wit J, Donker T. Preventie & eMental-Health. Onderzoek dat leidt, technologie die verleidt, preventie die bereikt en beklijft. Amsterdam: Vrije Universiteit Amsterdam; 2013.

26.

Smeets O, Martin Abello K, Zijlstra-Vlasveld M, Boon B. E-health in de GGZ: hoe staat het daar nu mee? Ned Tijdschr Geneeskd. 2014;158:A8589.PubMed

27.

Mouthaan J, Sijbrandij M, de Vries G-J, Reitsma BJ, van de Schoot R, Goslings CJ, et al. Internet-Based Early Intervention to Prevent Posttraumatic Stress Disorder in Injury Patients: Randomized Controlled Trial. J Med Internet Res. 2013;15(8):e165.CrossRefPubMedPubMedCentral

28.

Hippisley-Cox J, Coupland C, Vinogradova Y, Robson J, Minhas R, Sheikh A, et al. Predicting cardiovascular risk in England and Wales: prospective derivation and validation of QRISK2. Br Med J. 2008;336(7659):1475–82.CrossRef

29.

Moher D, Schulz K, Altman D. The CONSORT statement: revised recommendations for improving the quality of reports of parallel group randomized trials. BMC Med Res Methodol. 2001;1(1):2.CrossRefPubMedPubMedCentral

30.

Groeneveld IF, Proper KI, van der Beek AJ, van Mechelen W. Sustained body weight reduction by an individual-based lifestyle intervention for workers in the construction industry at risk for cardiovascular disease: Results of a randomized controlled trial. Prev Med. 2010;51(3–4):240–6.CrossRefPubMed

31.

Robroek S, Bredt F, Burdorf A. The (cost-)effectiveness of an individually tailored long-term worksite health promotion programme on physical activity and nutrition: design of a pragmatic cluster randomised controlled trial. BMC Public Health. 2007;7(1):259.CrossRefPubMedPubMedCentral

32.

Proper KI, Hildebrandt VH, Van der Beek AJ, Twisk JWR, Van Mechelen W. Effect of individual counseling on physical activity fitness and health: A randomized controlled trial in a workplace setting. Am J Prev Med. 2003;24(3):218–26.CrossRefPubMed

33.

Lin JS, O’Connor E, Whitlock EP, Beil TL. Behavioral Counseling to Promote Physical Activity and a Healthful Diet to Prevent Cardiovascular Disease in Adults: A Systematic Review for the U.S. Preventive Services Task Force. Ann Intern Med. 2010;153(11):736–50.CrossRefPubMed

34.

Robroek SJW, van den Berg TIJ, Plat JF, Burdorf A. The role of obesity and lifestyle behaviours in a productive workforce. Occup Environ Med. 2010;68(2):134–9.CrossRefPubMed

35.

Conroy RM, Pyörälä K, Fitzgerald AP, Sans S, Menotti A, De Backer G, et al. Estimation of ten-year risk of fatal cardiovascular disease in Europe: the SCORE project. Eur Heart J. 2003;24(11):987–1003.CrossRefPubMed

36.

D’Agostino RB, Vasan RS, Pencina MJ, Wolf PA, Cobain M, Massaro JM, et al. General Cardiovascular Risk Profile for Use in Primary Care: The Framingham Heart Study. Circulation. 2008;117(6):743–53.CrossRefPubMed

37.

Cardiovasculair risicomanagement (Tweede herziening). Nederlands Huisartsen Genootschap. Huisarts Wet. 2012. 55(1):14–28. https://www.nhg.org/standaarden/volledig/cardiovasculair-risicomanagement. Accessed May 2015.

38.

Van Binsbergen JJ, Langens FNM, Dapper ALM, Van Halteren MM, Glijsteen R, Cleyndert GA, et al. NHG-Standaard Obesitas. Huisarts Wet. 2010;53(11):609–25.

39.

Prochaska JO, Velicer WF. The transtheoretical model of health behavior change. Am J Health Promotion. 1997;12(1):38–48.CrossRefPubMed

40.

Joseph-Williams N, Newcombe R, Politi M, Durand M-A, Sivell S, Stacey D, et al. Toward Minimum Standards for Certifying Patient Decision Aids: A Modified Delphi Consensus Process. Med Decis Making. 2014;34(6):699–710.CrossRefPubMed

41.

Richtlijnen Nederlandse Vereniging voor Arbeids- en Bedrijfsgeneeskunde (NVAB). [https://www.nvab-online.nl/richtlijnen/richtlijnen-NVAB].

42.

Groeneveld IF, Proper K, van der Beek AJ, van Duivenbooden DC, van Mechelen W. Design of a RCT evaluating the (cost-) effectiveness of a lifestyle intervention for male construction workers at risk for cardiovascular disease: The Health under Construction study. BMC Public Health. 2008;8:1.CrossRefPubMedPubMedCentral

43.

Miller WR, Yahne CE, Moyers TB, Martinez J, Pirritano M. A Randomized Trial of Methods to Help Clinicians Learn Motivational Interviewing. J Consult Clin Psychol. 2004;72(6):1050–62.CrossRefPubMed

44.

Smith JL, Amrhein PC, Brooks AC, Carpenter KM, Levin D, Schreiber EA, et al. Providing Live Supervision Via Teleconferencing Improves Acquisition of Motivational Interviewing Skills After Workshop Attendance. Am J Drug Alcohol Abuse. 2007;33(1):163–8.CrossRefPubMed

45.

Moyers TB, Martin T, Manuel JK, Miller WR. The motivational interviewing treatment integrity (MITI) code: Version 2.0. Unpublished manuscript. Albuquerque, NM: University of New Mexico, Center on Alcoholism, Substance Abuse and Addictions; 2003.

46.

Forsberg L, Berman AH, Källmén H, Hermansson U, Helgason AR. A Test of the Validity of the Motivational Interviewing Treatment Integrity Code. Cogn Behav Ther. 2008;37(3):183–91.CrossRefPubMed

47.

Burke LE, Conroy MB, Sereika SM, Elci OU, Styn MA, Acharya SD, et al. The Effect of Electronic Self-Monitoring on Weight Loss and Dietary Intake: A Randomized Behavioral Weight Loss Trial. Obesity. 2011;19(2):338–44.CrossRefPubMed

48.

McHorney C, Ware J, Raczek A. The MOS 36-Item Short-Form Health Survey (SF-36): II. Psychometric and clinical tests of validity in measuring physical and mental health constructs. Med Care. 1993;31(3):247.CrossRefPubMed

49.

Group E. EuroQol--a new facility for the measurement of health-related quality of life. Health Policy. 1990;16(3):199–208.CrossRef

50.

Gek Huang Goh L, Welborn TA, Dhaliwal SS. Independent external validation of cardiovascular disease mortality in women utilising Framingham and SCORE risk models: a mortality follow-up study. BMC Womens Health. 2014;14:118.

51.

Wilson PWF, D’Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB. Prediction of Coronary Heart Disease Using Risk Factor Categories. Circulation. 1998;97(18):1837–47.CrossRefPubMed

52.

D’Agostino RB, Pencina MJ, Massaro JM, Coady S. Cardiovascular Disease Risk Assessment: Insights from Framingham. Global Heart. 2013;8(1):11–23.CrossRefPubMedPubMedCentral

53.

Chavannes NH, Kaper J, Frijling BD, Van der Laan JR, Jansen PWM, Guerrouj S, et al. NHG-Standaard Stoppen met roken. Huisarts Wet. 2007;50(7):306–14.

54.

Kemper H, Ooijendijk W, Stiggelbout M. Consensus over de Nederlandse Norm voor Gezond Bewegen. Tijdschr Soc Gezondheidsz. 2000;78:180–3.

55.

Health Council of the Netherlands. Guidelines for a healthy diet 2006. The Hague: Health Council of the Netherlands; 2006.

56.

Alavinia SM, van der Berg T, van Duivenbooden JC, Elders L, Burdorf A. Impact of work-related factors, lifestyle, and work ability on sickness absence among Dutch construction workers. Scand J Work Environ Health. 2009;35(2):325–33.CrossRefPubMed

57.

Ilmarinen J. The work ability index (WAI). Occup Med. 2007;57:160.CrossRef

58.

Brouwer WB, Koopmanschap MA, Rutten FF. Productivity losses without absence: measurement validation and empirical evidence. Health Policy. 1999;48:13–27.CrossRefPubMed

59.

Koopmanschap MA. PRODISQ: a modular questionnaire on productivity and disease for economic evaluation studies. Expert Rev Pharmacoecon Outcomes Res. 2005;5(1):23–8.CrossRefPubMed

60.

Noben C, Evers S, Nijhuis F, de Rijk A. Quality appraisal of generic self-reported instruments measuring health-related productivity changes: a systematic review. BMC Public Health. 2014;14(1):115.CrossRefPubMedPubMedCentral

61.

Lerner D, Amick III BC, Rogers WH, Malspeis S, Bungay K, Cynn D. The Work Limitations Questionnaire. Med Care. 2001;39(1):72–85.CrossRefPubMed

62.

Burton NW, Chen C-Y, Conti JD, Pransky G, Edington WD. Caregiving for Ill dependents of its association with employee health risks and productivity. J Occup Environ Med. 2004;46(10):1048–56.CrossRefPubMed

63.

Debra L, Benjamin A. The Work Limitations Questionnaire (WLQ): Development and Psychometric Performance and Bibliography. The Health Institute, Tufts Medical Center f/k/a/ New England Medical Center Hospitals, Inc., and Glaxo Wellcome, Inc. 1998, updated 20 October 2013.

64.

King DK, Glasgow RE, Leeman-Castillo B. Reaiming RE-AIM: Using the Model to Plan, Implement, and Evaluate the Effects of Environmental Change Approaches to Enhancing Population Health. Am J Public Health. 2010;100(11):2076–84.CrossRefPubMedPubMedCentral

65.

Kessler RS, Purcell EP, Glasgow RE, Klesges LM, Benkeser RM, Peek CJ. What Does It Mean to “Employ” the RE-AIM Model? Eval Health Prof. 2013;36(1):44–66.CrossRefPubMed

66.

Guzik A, Menzel NN, Fitzpatrick J, McNulty R. Patient Satisfaction with Nurse Practitioner and Physician Services in the Occupational Health Setting. AAOHN J. 2009;57(5):191–7.CrossRefPubMed

67.

Aaronson NK, Muller M, Cohen PDA, Essink-Bot M-L, Fekkes M, Sanderman R, et al. Translation, Validation, and Norming of the Dutch Language Version of the SF-36 Health Survey in Community and Chronic Disease Populations. J Clin Epidemiol. 1998;51(11):1055–68.CrossRefPubMed

68.

Eriksson MK, Hagberg L, Lindholm L, Malmgren-Olsson E, Österlind J, Eliasson M. Quality of life and cost-effectiveness of a 3-year trial of lifestyle intervention in primary health care. Arch Intern Med. 2010;170(16):1470–9.CrossRefPubMed

69.

Pruitt SL, Leonard T, Murdoch J, Hughes A, McQueen A, Gupta S. Neighborhood effects in a behavioral randomized controlled trial. Health Place. 2014;30:293–300.CrossRefPubMedPubMedCentral

70.

Dietz RD. The estimation of neighborhood effects in the social sciences: An interdisciplinary approach. Soc Sci Res. 2002;31(4):539–75.CrossRef

71.

Hollis S, Campbell F. What is meant by intention to treat analysis? Survey of published randomized controlled trials. Br Med J. 1999;319(7211):670–4.CrossRef

72.

Campbell MK, Elbourne DR, Altman DG. CONSORT statement: extension to cluster randomised trials. BMJ. 2004;328-702.

73.

Rubak S, Sandbæk A, Lauritzen T, Christensen B. Motivational interviewing: a systematic review and meta-analysis. Br J Gen Pract. April 2005;55(513):305-312.

74.

Rongen A, Robroek SJW, van Lenthe FJ, Burdorf A. Workplace Health Promotion: A Meta-Analysis of Effectiveness. Am J Prev Med. 2013;44(4):406–15.CrossRefPubMed

75.

Lustria MLA, Noar SM, Cortese J, Van Stee SK, Glueckauf RL, Lee J. A Meta-Analysis of Web-Delivered Tailored Health Behavior Change Interventions. J Health Commun. 2013;18(9):1039–69.CrossRefPubMed

76.

Lundahl B, Burke BL. The effectiveness and applicability of motivational interviewing: a practice-friendly review of four meta-analyses. J Clin Psychol. 2009;65(11):1232–45.CrossRefPubMed

77.

Sheeran P. Intention—Behavior Relations: A Conceptual and Empirical Review. Eur Rev Soc Psychol. 2002;12(1):1–36.CrossRef

78.

Rhodes RE, de Bruijn G-J. How big is the physical activity intention–behaviour gap? A meta-analysis using the action control framework. Br J Health Psychol. 2013;18(2):296–309.CrossRefPubMed

79.

Jackson C, Lawton R, Knapp P, Raynor DK, Conner M, Lowe C, et al. Beyond intention: do specific plans increase health behaviours in patients in primary care? A study of fruit and vegetable consumption. Soc Sci Med. 2005;60(10):2383–91.CrossRefPubMed

80.

Mann D, Lin J. Increasing efficacy of primary care-based counseling for diabetes prevention: Rationale and design of the ADAPT (Avoiding Diabetes Thru Action Plan Targeting) trial. Implement Sci. 2012;7(1):6.CrossRefPubMedPubMedCentral

81.

82.

Rahman M, Simmons RK, Hennings SH, Wareham NJ, Griffin SJ. Effect of screening for Type 2 diabetes on population-level self-rated health outcomes and measures of cardiovascular risk: 13-year follow-up of the Ely cohort. Diabet Med. 2012;29(7):886–92.CrossRefPubMedPubMedCentral

83.

Nilsen V, Bakke PS, Rohde G, Gallefoss F. Predictors of health-related quality of life changes after lifestyle intervention in persons at risk of type 2 diabetes mellitus. Qual Life Res. 2014;23(9):2585–93.CrossRefPubMedPubMedCentral

84.

van den Brink CL, Savelkoul M. Gezondheidsmonitor GGD’en, CBS en RIVM. Volksgezondheid Toekomst Verkenning, Nationaal Kompas Volksgezondheid. Bilthoven: RIVM; 2013.

85.

Reyes-Guzman CM, Bray RM, Forman-Hoffman VL, Williams J. Overweight and Obesity Trends Among Active Duty Military Personnel: A 13-Year Perspective. Am J Prev Med. 2015;48(2):145–53.CrossRefPubMed

86.

Rossomanno CI, Herrick JE, Kirk SM, Kirk EP. A 6-Month Supervised Employer-Based Minimal Exercise Program for Police Officers Improves Fitness. J Strength & Conditioning Res. 2012;26(9):2338–44.CrossRef

87.

Lambert BS, Oliver JM, Katts GR, Green JS, Martin SE, Crouse SF. DEXA or BMI: Clinical Considerations for Evaluating Obesity in Collegiate Division I-A American Football Athletes. Clin J Sport Med. 2012;22(5):436–8.CrossRefPubMed

Title: Design and baseline characteristics of the PerfectFit study: a multicenter cluster-randomized trial of a lifestyle intervention in employees with increased cardiovascular risk
Authors: Tessa A. Kouwenhoven-Pasmooij
Bosiljka Djikanovic
Suzan J. W. Robroek
Pieter Helmhout
Alex Burdorf
M. G. Myriam Hunink
Publication date: 01-12-2015
Publisher: BioMed Central
Published in: BMC Public Health / Issue 1/2015
Electronic ISSN: 1471-2458
DOI: https://doi.org/10.1186/s12889-015-2059-9

Keynote webinar | Spotlight on sleep in brain health

Springer Medicine

Design and baseline characteristics of the PerfectFit study: a multicenter cluster-randomized trial of a lifestyle intervention in employees with increased cardiovascular risk

Abstract

Background

Methods

Discussion

Trial registration

Keynote webinar | Spotlight on sleep in brain health

Springer Medicine

Abstract

Background

Methods

Discussion

Trial registration

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