Heat does impair thinking in manual workers, but the comparison is missing
The studies here consistently find that heat stress degrades cognitive performance in people doing physical work. In a field study of petrochemical workers on 12-hour rotating shifts, heat stress measured with a standard index was linked to more commission errors, slower response times, and fewer correct responses, with performance generally worst at the end of the shift [2]. A laboratory study of construction workers doing simulated manual work found impaired performance on a demanding working-memory task in hot conditions compared with temperate ones [3]. A scoping review maps the same concern for outdoor workers, framing them as a cognitively vulnerable group [4].
None of these studies, however, puts manual workers and office workers side by side under the same heat exposure. The petrochemical study compared heat-exposed groups with a control group but did not contrast manual and office occupations [2]. The construction study compared hot and temperate conditions within the same group of manual workers [3]. The review covers outdoor workers only [4]. A separate EEG study of heat-exposed manual workers explicitly notes that earlier work was limited to young indoor office workers, but it does not itself compare the two groups [1]. So the direct question remains open.
The task matters more than the label on the job
The clearest pattern across these studies is that heat hits harder tasks first. In the construction study, simple attention and simple memory tests showed no significant difference between hot and temperate conditions, while the more complex memory task was impaired in the heat [3]. A review of indoor heat studies in office-like settings reached the same conclusion: complex tasks are more susceptible than simple ones under identical conditions, and heat intensity interacts with how long someone is exposed [5].
That reframes the manual-versus-office question. If vulnerability depends heavily on what the task demands, then a manual worker doing a complex safety-critical task in heat and an office worker doing a complex task in a hot room may face a similar cognitive risk, while a manual worker doing a simple repetitive task may face less. The evidence supports task complexity as a strong modifier of heat effects [3][5], but it does not test that comparison across occupations.
Physical work in heat adds a load that desk work does not
Manual work in heat is not just heat exposure; it is heat plus exertion. The construction study examined cognitive performance while participants performed manual simulated work, and it also tracked mental and physical task demands and thermal perceptions alongside cognition [3]. That design reflects the reality that physical effort and heat arrive together for these workers, which is a different situation from a person sitting still in a warm office.
The indoor review describes its settings as low-intensity activity typical of offices and homes, and it points to a speed-accuracy trade-off under heat that is likely driven by psychological effects, with factors such as age, gender, expectation, and motivation modulating the outcome [5]. Those human factors are presented as possible influences rather than proven causes. The contrast in activity level between the two literatures is real, but no study here isolates physical exertion as the reason manual workers might be more affected.
What a fair comparison would need to measure
To answer the original question properly, a study would need manual and office workers exposed to the same measured heat stress, doing comparable cognitive tasks, with performance tracked over the shift. The petrochemical study shows one workable approach: measuring heat with a standard index at the start, middle, and end of the shift while running attention and working-memory tests at those same points [2]. The construction study shows another: controlled hot versus temperate conditions with tasks of graded difficulty [3].
The indoor review adds a further suggestion, calling for brain-activity measures combined with cognitive tasks under heat, plus tailored exposure limits and cooling strategies [5]. The EEG study of manual workers is a step in that direction, using brain recordings to examine cognitive vulnerability in heat-exposed manual workers [1]. Until such designs include both occupational groups, the most defensible reading is that heat impairs cognition in manual workers, that complex tasks suffer most, and that a direct manual-versus-office comparison at matched heat stress has not yet been made.
Sources used in this answer
Thermal stress and cognitive performance in heat-exposed manual workers: An EEG investigation in a controlled indoor environment
An EEG study examined cognitive vulnerability to heat stress in middle-aged heat-exposed manual workers but did not compare them with office workers.
Evaluating the effect of heat stress on cognitive performance of petrochemical workers: A field study
In petrochemical workers across 12-hour shifts, heat stress was associated with more commission errors, slower response times, and fewer correct responses, with cognitive performance generally lower at the end of the shift.
Evaluating the effect of physical work in the heat on cognitive performance of construction workers
Construction workers doing simulated manual work in hot conditions showed impaired performance on a complex working-memory task but no significant difference on simple attention and memory tests compared with temperate conditions.
Heat stress and Neurobehavioral performance in outdoor workers exposed to Heat stress
A scoping review maps evidence on heat stress and cognitive functioning in outdoor workers and frames them as a vulnerable group, without comparing them with office workers.
How heat stress impairs cognition: A review of cognitive performance in indoor passive hyperthermal environments
A review of indoor heat studies in office-like settings reports a speed-accuracy trade-off, greater susceptibility of complex tasks, and modulation by human factors such as age, gender, expectation, and motivation.