Prospective cohort, 2,400 workers, 6 years

Cohort study poster example

A cohort study poster has to show change over time in the same people, so the follow up waves carry the board. This A0 landscape example follows 2,400 hospital and factory workers for six years, 1,200 on rotating shifts and 1,200 on day work, and reports new hypertension with an adjusted hazard ratio of 1.5, 95% CI 1.2 to 1.9.

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The whole board

The poster at full size, exactly as it prints. Every number, citation and caption on it was written for this example, so the layout is being judged on real content.

QU
Does rotating shift work raise blood pressure? A six year prospective cohort of 2,400 hospital and factory workers
N. Ashdown ¹, T. Okonjo ¹, R. Lindqvist ¹ ²
1 School of Population Health, Quillmere University · 2 Occupational Health Unit, Quillmere University
9% and 9%
Baseline
Hypertension at entry, shift and day groups
13% and 11%
Year 2
Shift workers pull 2 points ahead
18% and 14%
Year 4
The gap widens to 4 points
24% and 17%
Year 6
A 7 point gap after six years
Abstract
We followed 2,400 workers for six years, 1,200 on rotating shifts and 1,200 on day work only. Among the 2,118 seen at every wave, hypertension rose from 9% to 24% on shifts and from 9% to 17% on days. Adjusted hazard ratio 1.5.
METHODS
Design. Prospective cohort, four clinic waves at baseline, 2, 4 and 6 years, 2020 to 2026.
Cohort. 2,400 workers aged 25 to 55 from 4 hospitals and 3 food plants: 1,200 on rotating shifts with 4 or more nights a month, 1,200 on day work only.
Outcome. Hypertension: the mean of two seated clinic readings at 140/90 or above, or a new prescription for blood pressure medicine.
Retention. 2,118 seen at all four waves (88%): 1,052 shift and 1,066 day. 148 shift and 134 day workers left the cohort.
Analysis. Cox model for new hypertension in the 1,927 free of it at entry, adjusted for age, sex, body mass index, smoking and baseline pressure.
REFERENCES
1.Ferraby, J. and Mutasa, L. (2023) Night work and blood pressure in hospital staff. Journal of Occupational Cardiology, 14(3), 201 to 219.
2.Halvorsen, E. (2024) Healthy worker survivor bias in shift work cohorts. Occupational Epidemiology Methods, 9(1), 33 to 52.
3.Ashdown, N. (2025) Clinic blood pressure protocols for workplace cohorts. Quillmere Health Report 6, 2025.
Shift work
Day work
0%5%10%15%20%
Figure 1. New hypertension since entry, %, in 957 shift and 970 day workers free of it at baseline. Bars left to right: years 2, 4 and 6.
Source: cohort clinic waves, 2020 to 2026.
Results
Of the 2,118 workers seen at every wave, 95 of 1,052 on shifts and 96 of 1,066 on days had hypertension at entry, 9% in both groups. By year 6 the counts were 252 and 181, or 24% and 17%. Among the 957 shift and 970 day workers free of hypertension at entry, 157 and 85 developed it, a cumulative incidence of 16.4% against 8.8%. The crude hazard ratio was 1.9. Adjusting for age, sex, body mass index, smoking and baseline pressure brought it to 1.5, 95% CI 1.2 to 1.9, because shift workers were slightly older and smoked more at entry. The gap opened by year 2 and widened at every wave after that. Workers with more than 8 nights a month carried most of the excess, with an adjusted ratio of 1.8 against 1.3 for those working 4 to 8 nights.
HR 1.5
adjusted hazard of new hypertension, shift against day work
95% CI 1.2 to 1.9; crude 1.9; 157 of 957 against 85 of 970 new cases
Key finding
Rotating shifts carried a 50% higher adjusted risk of new hypertension over six years.
Discussion
A cohort answers what a single survey cannot: blood pressure was normal in both groups at entry and the gap opened afterwards, wave by wave. The dose pattern, with more nights carrying more risk, makes chance a weaker explanation. Two limits matter. Workers who found shifts hard may have moved to day work, so the shift group is a survivor group and the true effect may be larger. And 282 workers left the cohort, 148 from shifts, so the 2,118 retained are not the whole picture. Every clinic reading was taken before a day shift, so time of day did not differ between the groups.
Hypertension rose from 9% to 24% on shifts, 9% to 17% on days
New cases 157 of 957 shift against 85 of 970 day workers
Adjusted hazard ratio 1.5, 95% CI 1.2 to 1.9
More than 8 nights a month carried most of the excess

Block by block

What each block on the board is for, in the order a reader walks it.

Title band and three authors
The title asks the question the cohort answers and names the 2,400 workers. Three authors share two affiliations at the fictional Quillmere University.
Findings timeline across the top
Four stops at baseline and years 2, 4 and 6 give the share with hypertension in each group: 9% and 9%, 13% and 11%, 18% and 14%, then 24% and 17%. A reader sees the gap open before reading a word of method.
Abstract and methods
A short abstract, then five labelled method entries: design, the cohort and how exposure was defined, the outcome, retention of 2,118 of 2,400 and the Cox model with its adjustments.
Figure 1 and results
Grouped bars give new hypertension among the 957 shift and 970 day workers free of it at entry, at years 2, 4 and 6. The results block gives every count behind the percentages and the crude ratio of 1.9 beside the adjusted 1.5.
Key number and key finding
The stat block carries the adjusted hazard ratio with its interval and the raw counts. The callout puts the result in one sentence.
Discussion, takeaways and references
The discussion names healthy worker survivor bias and the 282 who left. Four checked takeaways and three references close the board.

What makes this board work

The timeline does the work of a table

The four timeline stops hold eight percentages, so the six year story reads across the top of the board. The same numbers rebuild from counts in the results: 95 to 252 of 1,052 shift workers, 96 to 181 of 1,066 on days.

Crude and adjusted side by side

The board gives the crude hazard ratio of 1.9 next to the adjusted 1.5 and says why they differ: shift workers were older and smoked more at entry. Showing both stops a reader suspecting the adjustment was chosen to suit.

Losses are counted, not hidden

Retention is its own method entry: 2,118 of 2,400 seen at every wave, 88%, with 148 shift and 134 day workers lost. The discussion then says which way that loss could bias the result.

Questions people ask

Should a cohort poster show incidence or prevalence?

Show the one your question needs and label it plainly. This board uses both: the timeline gives the share with hypertension at each wave, which includes people who had it at entry, and the figure gives new cases only among the 1,927 who were free of it. Mixing the two without labels is the most common way a cohort poster misleads.

Why does the board give a crude and an adjusted hazard ratio?

Because the groups differed at entry. The crude ratio of 1.9 compares shift and day workers as they were; the adjusted 1.5 compares them as if age, sex, body mass index, smoking and baseline pressure were equal. Reporting only the adjusted figure hides how much the adjustment moved it, which reviewers want to see.

Where do follow up losses go on a cohort poster?

In the methods, as a count per group, and again in the discussion with the direction of any bias. Here 282 of 2,400 left, 148 from shifts. A flow diagram suits a trial better; on a cohort board one retention line carries the same information in far less space.

Can the timeline plot more than four waves?

Not on this layout. The findings timeline has four fixed stops, each with a number, a name and a short line, so a fifth wave would have to go in the results text or the figure. A study with many waves suits a layout led by a large chart instead, where every wave becomes a category on the axis.

How big does a cohort poster print?

This board is A0 landscape, 1189 by 841 millimetres. The builder exports at twice its working canvas, 4,680 by 3,312 pixels, which is about 100 dots per inch at full size, in RGB with no bleed or crop marks. That reads cleanly at arm length; ask the printer before sending it to a press that expects more.

What makes a cohort design worth stating on the poster?

Time order. Both groups started with the same 9% prevalence and the gap opened afterwards, wave by wave, which a single survey cannot show. Put the design in the title or the first method entry so a passing reader knows the result is about change in the same people, not a comparison taken at one moment.

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