ART and Impaired Presenteeism Among Kenyan Agricultural Workers Bruce A. Larson 1, Matthew P. Fox 1, Sydney Rosen 1, Margaret Bii 2, Carolyne Sigei 2, Douglas Shaffer 3, Fredrick Sawe 2, Monique Wasunna 2, Kelly McCoy 1, and Jonathon L. Simon 1 1. Boston University (School of Public Health, Center for International Health and Development) 2. Kenya Medical Research Institute 3. Walter Reed Army Institute of Research Center for International Health and Development 1
Background and Methods
Background Four years ago, we estimated the impact of HIV/AIDS on the work performance of an untreated population of tea plantation workers in Kericho, Kenya (Fox et al. 2004). Treatment with antiretroviral medications (ART) was introduced at the tea companies hospitals in 2004 with PEPFAR funding. In 2005 we began a new study to explore the impacts of ART on work performance and other non-clinical outcomes. Results presented today answer the question, To what degree does ART restore and maintain physical functioning so that an individual can return to or continue with his or her normal daily activities (tea harvesting)? 3
Hypotheses: How might HIV/AIDS and ART affect work performance over time? HIV-infected but pre-art: Work fewer days (absenteeism) as HIV infection and illness progress. Adjust work activities, e.g. by shifting to non-plucking tasks or harvesting less per day (more impaired presenteeism). HIV-infected and post-art: Work more days (less absenteeism); maybe return to levels found in the general workforce? Adjust work activities e.g. toward more plucking, fewer non-plucking days, harvesting more when plucking (less impaired presenteeism). 4
Study site Two large tea plantations in Kericho District participating in the study (also tea factories, timber, flowers, elevation about 7,000 feet) (Larson et. al, 2008, AIDS, 22: 421-425). Both companies provide free medical care to workers and dependents, transportation. Data today are from one company. Focus is on workers whose primary responsibility is plucking tea. 5
Study Populations Retrospective/prospective cohort study design with intervention and comparison groups Inclusion criteria for Intervention/Treatment Group (IG): adult tea pluckers permanent staff on ART or likely soon to be on ART after enrollment written consent to participate target sample size = 294 in IG. Today s results based on initial IG: n = 59 (26 men, 33 women) initiated ART between April 2004 and December 2005 hired before 2002. 6
Study Population Comparison Group (CG) population of adult tea pluckers working in same gangs as the workers in the IG gangs work in same fields on the same days (matching on date and field) HIV status of CG is unknown (14% estimated in general population in region). Today s results based on initial CG: n = 1992 (1306 men, 686 women) also hired before 2002. 7
Data Extracted individual information from company payroll records (by estate within plantation). Payroll records contain daily values for all past and current employees from 2001 to present (millions of records per estate). If plucked that day, quantity harvested. If did not pluck, then worked other non-plucking tasks? If neither, then not at work (separate data sets for leave/absenteeism). Collapsed daily observations to monthly unit of analysis. Final outcome variables for this analysis: Number of days worked plucking tea each month Number of days working non-plucking assignments On days plucking in the month, the average kilograms harvested. 8
Methods -- How to compare work histories of IG and CG workers? Months on ART IG worker and all CG workers in same gang IG worker Gang 10 began ART -24 0 12 4/02 12/05 12/06 12/03 Calendar time 9
Analysis: Nearest neighbor matching For each outcome and each study month, used nearest neighbor matching methods to estimate the sample average treatment effects on the treated. For each study month, each IG worker matched to 4 CG workers based on gang, age, sex, and years employed. Once the matches in the CG are identified, the matching estimator is essentially the difference between the IG and matched CG sample means. The bias-corrected version of the matching estimator is used to adjust for imperfect matching (e.g. on age or years of employed). Robust variance estimates used to adjust for possible heteroskedasticity (also with 4 CG matches). Used nnmatch in STATA 10. Observed different work patterns between men and women, so also compared males to males and females to females for each outcome. 10
Results and Discussion
Study groups Men Women CG IG CG IG number 1306 26 686 33 Age in Years (1/1/06) Experience (1/1/06) CD4 for ART 39.2 41.6 41.1 41.4 11.3 10.8 11.6 10.9 median 140.0 178 IQR 82-228 86-251 12
Mean days plucking and non-plucking assignments (men) 25 P < 0.05 Mean Days Per Month Each Outcome 20 15 10 5 0-24 -21-18 -15-12 -9-6 -3 0 3 6 9 12 Months Relative to ART Initiation Intervention Group (Plucking) Intervention Group (Non-Plucking) Comparison Group (Plucking) Comparison Group (Non-Plucking) 13
Mean days plucking and non-plucking assignments (women) 25 P < 0.05 20 Mean Days Per Month 15 10 5 0-24 -21-18 -15-12 -9-6 -3 0 3 6 9 12 Months Relative to ART Initiation Intervention Group (Plucking) Intervention Group (Non-Plucking) Comparison Group (Plucking) Comparison Group (Non-Plucking) 14
Quantity harvested when plucking Men CG mean across all months = 42 kg/day. IG mean across all months = 39 kg/day (7% less). Differences were significant (p < 0.05) in months -20, -13, -7, -4, -2, 0. Women CG mean across all months = 34.4 kg/day. IG mean across all months = 30.4 kg/day (12% less). Differences were significant (p < 0.05) in months -24, -18, -15, -14, -13, -12, -3, 0, 12. These are months before impacts generally observed in plucking and non-plucking days. 15
Discussion Observed pattern of presenteeism very different for men and women. For men: No significant increase in impaired presenteeism in the pre-art period. After a substantial decline in days plucking during the initial 3 months on ART, no difference in IG and CG work outcomes from month 4 to month 12. How long can men on ART sustain such outcomes on ART? 16
Discussion For women: Substantial impacts observed beginning in the second year pre-art through one year on ART. harvested less when plucking (mainly during second year pre-art) more non-plucking assignments beginning in month -7 and remaining high through one year on ART (450% more than CG in month 12) fewer days plucking tea beginning in month -12 through month 0 (IG = 5 days, GC = 20 days) increase in days plucking during first year on ART, but IG still working 30% fewer days than the CG in month 12. Why results for women so different than men? 17
Limitations Small sample size (now have 294 in the intervention group, working on data) Longer follow up: will continue to two years on ART with current funding; if new funding obtained, will follow longer. HIV+ workers who started ART but died before study began not included (could not consent). For those who consented, however, there were no deaths during this study period. 18
Acknowledgements Participating tea companies and workers. Company medical and human resource staff. Fogarty International Center of the U.S. National Institutes of Health. PEPFAR team in Kericho. Ethics approvals from KEMRI, WRAIR, and BU. 19