PUBH 6036 Week 3 Design Comparison Example

Forward From the Bedroom or Backward From the Attendance Office? A Design Comparison of a Cohort and a Case-Control Study for Bed Bug Infestation and School Absence in a Composite Housing Authority

Student Name

Walden University

PUBH 6036: Public Health Research Methods

Instructor Name

Month Day, Year

Forward From the Bedroom or Backward From the Attendance Office? A Design Comparison of a Cohort and a Case-Control Study for Bed Bug Infestation and School Absence in a Composite Housing Authority

The Question Both Designs Must Serve

The question settled in Week 1 asks whether children aged 6 to 12 in the Cedar Hollow Housing Authority's nine family buildings who live with a confirmed bed bug infestation at the start of a school year miss more school days over that year than children who do not. Two observational designs could answer it. A cohort study would confirm infestation status in the fall and follow every enrolled child through June. A case-control study would start at the other end, with children who had many absences and children who had few, and look back to learn whether their homes had been infested. This paper gives each design a fair hearing, chooses the cohort and states plainly what that choice costs.

The Cohort Design

In a cohort study, participants are classified by exposure first and followed to see who develops the outcome (Grimes & Schulz, 2002). Here the starting point would be a home visit in September. A trained inspector would check beds, sofas and baseboards, and interceptor cups would sit under bed and furniture legs for a week. Each child would be classed as living in an infested or uninfested apartment. With caregiver permission, the school district would then supply attendance for the full year.

What the Cohort Gains

The most important gain is order. Infestation is recorded before any absence is counted, so the design can show that exposure came first. That is one condition for a causal reading and cannot be achieved by a design that measures both at once. The second gain is a measured exposure. Because inspection happens before outcomes are known, the inspector cannot be influenced by knowing which child struggled at school. The third gain is flexibility. One cohort can study several outcomes at once: total absences, absences on Mondays, nurse visits for skin complaints and tardy arrivals.

What the Cohort Costs

The cohort is slow and expensive. Every enrolled household needs a fall visit and a week of monitoring, and the study cannot report until June. It also depends on how common the exposure is. In 43 low-income buildings in New Jersey, the overall apartment infestation rate was 12.3% (Wang et al., 2016). If Cedar Hollow is similar, only about one child in eight would be exposed, so a large number of homes must be inspected to collect enough exposed children for a clear comparison. Families also move, and infestation itself may push families to leave, which would remove exactly the children the study most needs to follow. Finally, exposure can change during the year. An apartment clear in September may be infested by January.

The Case-Control Design

A case-control study selects people by outcome and compares their past exposures (Schulz & Grimes, 2002). Cases would be children with high absence, such as missing at least a tenth of the school calendar, about 18 days of 180, which many districts call chronic absence. Controls would be children from the same buildings with fewer absences. Investigators would then ask whether each child's home had been infested during the year.

What the Case-Control Design Gains

It is fast and cheap. The attendance office already holds the outcome, so cases can be found in a few weeks. It handles rare outcomes well: if chronic absence were uncommon, sampling on it would collect cases efficiently. It also needs fewer home visits, because only cases and selected controls are studied.

What It Costs Here

The decisive cost is exposure measurement. By the time a child is selected as a case, the school year is over. Infestation during the year could be measured only by asking caregivers to remember, or by inspecting the home after the fact, when the insects may have been treated or may have arrived only recently. Memory is unreliable here in a particular way. In the New Jersey survey, 49% of the infestations the inspection protocol uncovered belonged to tenants who had no idea their apartment was affected (Wang et al., 2016). Caregivers of children with many absences may also search harder for an explanation and be more likely to recall bites, producing recall bias that inflates the association. Schulz and Grimes (2002) name this as one of the chief weaknesses of the design. A second cost is control selection. Controls must be drawn from the very families and buildings that gave rise to the cases; choosing them from a single building or a single classroom would distort the comparison.

Table 1

The Two Designs Side by Side for the Cedar Hollow Question

Note. Comparison prepared for this course; features adapted from Grimes and Schulz (2002) and Schulz and Grimes (2002).

Threats Neither Design Escapes

Some problems follow the question into either design. Crowding is one: apartments with more people may be more likely to host bed bugs and more likely to have children sharing beds and losing sleep for reasons unrelated to insects. A caregiver working nights is another, since it can affect both who notices insects and whether a child gets to school on time. Both designs must collect these conditions and adjust for them. Absence itself is also imperfect in both: an attendance record shows that a child was not in class but not why. Neither design can sort sick days from days lost to a family move or a missed bus. Naming these shared threats, and planning to measure them at the first visit, keeps the comparison honest, because the choice between designs does not solve them.

The Choice

The cohort is chosen. The question asks whether infestation at the start of a year relates to absences over that year, and only the cohort records the infestation before the absences occur. The case-control design would be quicker but would rest on the weakest part of the evidence, caregivers' memory of an insect that half of residents never notice.

What the Cohort Choice Pays

The choice costs a year, a large number of fall visits to find enough exposed children and a constant effort to keep in touch with families who move. It also leaves exposure fixed at one point while infestations come and go. The protocol will respond with a second monitoring visit in January, so that children whose homes became infested midyear can be identified and analyzed separately. These costs are stated here, in the same section as the choice, so that later readers can judge whether they were worth paying.

Conclusion

Both designs could produce an estimate. Only one can show which came first, and only one measures the exposure before anyone knows the outcome. For a question about whether living with bed bugs at the start of a school year relates to missed days later, the cohort fits, and its slowness is the price of that fit.

References

Grimes, D. A., & Schulz, K. F. (2002). Cohort studies: Marching towards outcomes. The Lancet, 359(9303), 341-345. https://doi.org/10.1016/S0140-6736(02)07500-1

Schulz, K. F., & Grimes, D. A. (2002). Case-control studies: Research in reverse. The Lancet, 359(9304), 431-434. https://doi.org/10.1016/S0140-6736(02)07605-5

Wang, C., Singh, N., Zha, C., & Cooper, R. (2016). Bed bugs: Prevalence in low-income communities, resident's reactions, and implementation of a low-cost inspection protocol. Journal of Medical Entomology, 53(3), 639-646. https://doi.org/10.1093/jme/tjw018