Self-reported effects of warm seasonal temperatures in persons with spinal cord injury

Abstract

Objective

Spinal cord injury (SCI) interrupts motor, sensory, and autonomic pathways, impairing mobility and increasing heat storage during warm seasonal temperatures due to compromised autonomic control of vasodilation and sweating and recognition of body temperature. Thus, persons with SCI are more vulnerable to hyperthermia and its adverse effects. However, information regarding how persons with SCI perceive warmer seasons and whether thermal discomfort during warmer seasons restricts routine activities remains anecdotal.

Design

Cross-sectional, self-report surveys.

Setting

VA Medical Center and Kessler Institute for Rehabilitation.

Participants

Three groups of 50 participants each: tetraplegia, paraplegia, and matched non-SCI controls.

Outcome Measures

Tetraplegia, paraplegia, and control groups responded “yes” or “no” when asked whether warm seasonal temperatures adversely affected comfort or participation in routine activities.

Results

The percentage of responses differed among tetraplegia, paraplegia, and control groups when asked if they required ≥20 min to cool down once overheated (44 vs. 20 vs. 12%; X²= 14.7, P < 0.001), whether heat-related discomfort limited their ability to go outside (62 vs. 34 vs. 32%; X²= 11.5, P = 0.003), if they needed to use a water-mister because of the heat (70 vs. 44 vs. 42%; X²= 9.8, P = 0.008), and if heat-related discomfort limited participation in social activities (40 vs. 20 vs. 16%; X²= 8.7, P = 0.01).

Conclusion

Warmer seasonal temperatures had a greater negative impact on reported comfort and daily activities of persons with SCI than non-SCI controls. Those with tetraplegia were most adversely affected. Our findings warrant increasing awareness and identifying interventions to address the vulnerability of persons with SCI to hyperthermia.

Introduction

Thermoregulation, or the maintenance of core body temperature (Tcore), is a unique physiological adaption among homeostatic systems in that it is one of the most tightly regulated systems. Of note, thermoregulation relies on cortical awareness of temperature sensation for behavioral adjustments such as adding or removing clothing and/or seeking cooler or warmer environments to assist the individual maintain Tcore within a narrow zone (37 ± 0.06°C), despite a wide range of thermal challenges (1–4).

When able-bodied persons are exposed to ambient heat, cutaneous and central thermoreceptors relay warm temperature information to the preoptic anterior hypothalamus (POAH), which processes skin, core, and hypothalamic temperatures. If those temperatures exceed the narrow set-point range (neutral zone), the POAH will increase blood flow to the skin (by inhibiting sympathetic adrenergic-mediated vasoconstriction and activating cholinergic-mediated vasodilation) to increase heat dissipation, and inhibit shivering to limit thermogenesis (4–6). If additional heat dissipation is needed, the POAH will initiate sweating (by upregulating sympathetic cholinergic-meditated sudomotor pathways) to increase evaporative cooling. Sweating is a very effective heat-loss mechanism during exposure to warmer temperatures at relative humidity levels ≤65%, but it is progressively less effective as levels exceed 65% (7, 8).

Spinal cord injury (SCI) interrupts motor, sensory, and autonomic pathways causing paralysis and decreased muscle mass, resulting in an impaired ability to shiver or move to more comfortable surroundings and impaired sensation of skin temperature below the neurological level of injury (NLI), limiting awareness of ambient temperatures. These interruptions impair the ability to invoke hypothalamic thermoregulatory mechanisms, which respond by modulating vasomotor tone and sudomotor activity, thus limiting the ability to conserve or dissipate body heat (9–11). The degree of neurological interruption increases with higher and more complete levels of injury. Therefore, persons with higher and more complete levels of SCI (≥ T6 with greater motor/sensory impairment) are especially vulnerable to hypothermia (Tcore ≤35°C) and hyperthermia (Tcore ≥38°C) and their adverse effects, during seasonal changes in temperature (3, 11–13).

Little is known with respect to the impact of thermodysregulation on quality of life (QOL) in persons with SCI. The SCI Quality of Life Measurement System (SCI-QOL) and Blood Pressure Dysregulation Measurement System (BPD-MS) are tools that quantify the impact of the interruption of motor, sensory, and autonomic pathways on QOL in specific areas after SCI (14, 15). The SCI-QOL is a patient-centered subjective measurement system that assesses the association between SCI-specific domains of functioning and well-being (i.e. bowel/bladder dysfunction, pressure ulcers, pain, emotional health, social participation, and physical functioning) on health-related QOL (14). The BPD-MS evaluates the impact of high blood pressure (autonomic dysreflexia) and low blood pressure (chronic and orthostatic hypotension) on health-related QOL, and describes the impact of low blood pressure on activities of daily living (ADLs) (15). However, neither of these SCI specific measures assess how impaired temperature tolerance after SCI affects QOL.

Heinemann et al., (16) found that of 18 perceived barriers to QOL in different settings, “feeling too hot or cold outdoors” was the most frequently reported barrier, while “feeling hot or cold at home” was the fourth most common barrier reported by 570 participants with neurological injuries (SCI: n = 193). Our previous work that applied subjective surveys, established that persons with tetraplegia reported seasonal cold exposure negatively impacted their QOL by affecting their personal comfort, sleep, ability to perform ADLs (e.g. bathing) and instrumental ADLs (IADLs) (e.g. keeping physician appointments) (17). However, information on the impact of warm seasonal temperatures on QOL from the perspective of persons with SCI is limited. The aim of our study was to determine if warmer seasons affect persons with tetraplegia, paraplegia, and non-SCI controls differently with respect to personal comfort or performance of ADL/IADLs, all of which contribute to determining the QOL for an individual.

Methods

The study design was cross-sectional, self-report surveys.

Participants

Fifty persons with tetraplegia (male [n = 40], female [n = 10], NLI C3-8; American Spinal Injury Association [ASIA] Impairment Scale [AIS] A [n = 13], B [n = 17], C [n = 12], D [n = 6], Undefined [n = 2]), 50 persons with paraplegia (male [n = 41], female [n = 9], NLI T1-12; AIS A [n = 30], B [n = 10], C [n = 5], D [n = 2], Undefined [n = 3]), and 50 matched, non-SCI controls (male [n = 39], female [n = 11]) from the New York and New Jersey area were recruited for study participation (Table 1). Inclusion criteria: SCI participants had a NLI between C3-T12, duration of SCI >1 year, and were between 18 and 75 years of age. Non-SCI controls were age (±5 years) and sex matched. Exclusion criteria: acute illness or infection, currently prescribed α adrenergic agonist medication or other medication that may alter vascular tone, pregnant women, untreated thyroid disease, chronic disease, or drug abuse. Participants volunteered to be part of the research study by signing an informed consent approved by either the James J. Peters Veterans Administration Medical Center (JPVAMC) or the Kessler Foundation Institutional Review Boards.

Table 1.

Characteristics of the tetraplegic, paraplegic, and control group.

Characteristic	Tetraplegia (n = 50) Mean ± SD	Paraplegia (n = 50) Mean ± SD	Controls (n = 50) Mean ± SD	P-value
Age (yrs)	43.6 ± 12.7	44.5 ± 12.6	40.7 ± 13.5	0.30
Height (m)	1.75 ± 0.11	1.78 ± 0.09	1.75 ± 0.08	0.10
Weight (kg)	77.93 ± 22.80	82.06 ± 19.16	81.76 ± 16.78	0.51
BMI (kg/m2)	24.7 ± 4.7	25.8 ± 5.6	26.7 ± 4.9	0.14
DOI (yrs)	14 ± 12.6	11.9 ± 10.2	NA	0.15
Male/Female	40/10	41/9	39/11	0.88

Group averages (± standard deviation) for age (years), height (meters), weight (kilograms), BMI, body mass index (kilograms/meter²), DOI, duration of injury (years), and number of male and female subjects.

Procedure

Participants were administered two surveys (Thermal Comfort, Thermal Activity). The survey questions were carefully constructed and based on the most frequent complaints reported by research participants to our investigators in prior studies during the warmer months of the year. The selected questions also obtained feedback from prior participants, physicians, and research staff with SCI. However, our surveys were not validated using focus groups, formal interviews or other means of validation, as have been performed for other survey assessments for persons with SCI (15, 18, 19).

The goal of the Thermal Comfort Survey was to assess how comfortable participants felt in indoor and outdoor environments during the warmer seasons. Participants were asked to answer questions with respect to their typical feelings of discomfort in indoor and outdoor environments (e.g. whether they felt overheated or dizzy during a warm summer day and how much time they required to cool down and feel comfortable again). Similarly, the goal of the Thermal Activity Survey was to determine if, compared to the rest of the year, the warmer ambient environmental temperatures during late spring through early fall, negatively impacted the participant’s perceived difficulty when completing their routine ADL/IADLs, performing their work duties and productivity, as well as maintaining their scheduled physician appointments and usual social schedule. Participants responded “yes” or “no” when asked whether warmer ambient temperatures caused feelings of discomfort and whether this temperature-induced discomfort negatively impacted their participation in these activities.

The surveys were administered at either the JPVAMC in the Department of Veterans Affairs Rehabilitation Research & Development National Center for the Medical Consequences of Spinal Cord Injury or at the Kessler Institute for Rehabilitation. The survey was administered in the presence of a member of the investigator’s team or administered by phone, if travel was difficult for the participant. Participants were asked to explain what the question meant to them to reduce variability among respondents’ interpretation and to frame their answers based on their experience during the warmer months of the year.

Statistical analysis

A χ² test of homogeneity (3 × 2 contingency table) was employed to determine if the number of responses (either “yes” or “no”) differed among the three groups (tetraplegia, paraplegia, control). Statistical significance was set at an α of 0.05. Standardized residual analyses were conducted to determine the significance of the difference between observed and expected frequencies for “yes” or “no” responses of each group. Between-group differences (tetraplegia vs. paraplegia, tetraplegia vs. control, paraplegia vs. control) were determined using χ² (2 × 2 contingency tables) with adjusted P-values presented. Post hoc within-paraplegic-group comparisons (high-paraplegia [Hi-Para: SCI ≥ T6] vs. low-paraplegia (Lo-Para: SCI < T6] utilized χ² 2 × 2 contingency tables. Similar comparisons were made between Hi-Para and control groups. Bonferroni corrections were applied to control for multiplicity (i.e. correction for 6 comparisons or 3 comparisons). Data were analyzed using IBM SPSS software (version 26.0, IBM Corp., Armonk, NY, USA).

Results

The tetraplegic, paraplegic, and control groups were not significantly different for age, height, weight, or body mass index (Table 1).

Thermal comfort survey

For the questions that assessed the impact of seasonal warm temperatures on personal comfort, a significant overall difference in the percentages of participants that responded “yes”, existed among the tetraplegic, paraplegic, and control groups when asked the following questions: (1) if they required more than 20 min to cool down and return to feeling comfortable after feeling overheated from being outside on a hot day (44 vs. 20 vs. 12%, respectively; P = 0.001), and (2) if they felt lightheaded because they were overheated (58 vs. 38 vs. 28%, respectively; P = 0.008) (Fig. 1; Table 2).

Figure 1.

Percent (%) of participants in each group who responded “yes” to requiring 20 min or more to cool down once overheated (Thermal Comfort Survey). The percentage of participants with tetraplegia who responded “yes” was significantly higher than expected, while the percentage of non-SCI controls who responded “yes” was significantly lower than expected. The percentage of “yes” responses in the tetraplegic group was significantly higher compared to the paraplegic group and control group. Dagger (†) indicates significant within-group difference compared to the null hypothesis († P < 0.05; †† p < 0.01). Asterisk (*) indicates significant between-group comparison (* P < 0.05; ** P < 0.01).

Table 2.

Three group (Tetra, Para, Control): comparisons of “yes” responses.

Question	Tetra(% “yes”)	Para(% “yes”)	Control(% “yes”)	Chi-Square(χ2)	# of “yes” Responses(Observed vs. Expected)	Pairwisecomparisons
Thermal Comfort
(1) Delayed cooling	44*	20	12*	14.7 (P = 0.001)	T: 22 vs. 12.7 (P = 0.001) C: 6 vs. 12.7 (P = 0.04)	T > C (P = 0.001)T > P (P = 0.03)
(2) Feeling dizzy	58*	38	28	9.6 (P = 0.008)	T: 29 vs. 20.7 (P = 0.02)	T > C (P = 0.007)
Thermal Activity
(1) Staying indoors barrier	24	10	8	6.3 (P = 0.04)	NS	NS
(2) Going outdoors barrier	62*	34	32	11.5 (P = 0.003)	T: 31 vs. 21.3(P = 0.004)	T > C (P = 0.008)T > P (P = 0.02)
(3) Using a mister	70*	44	42	9.8 (P = 0.008)	T: 35 vs. 26 (P = 0.01)	T > C (P = 0.01)T > P (P = 0.03)
(4) Wearing more clothes indoors	34*	22	4*	14.3 (P = 0.001)	T: 17 vs. 10 (P = 0.02)C: 4 vs. 10 (P = 0.003)	T > C (P = 0.0004)P > C (P = 0.02)
(5) Wearing more clothes outdoors	34*	14	12	9.3 (P = 0.01)	T: 17 vs. 10 (P = 0.02)	T > C (P = 0.03)
(6) Social barrier outdoors	40*	20	16	8.7 (P = 0.01)	T: 20 vs. 12.7 (P = 0.02)	T > C (P = 0.02)
(7) MD appt barrier	26	10	12	5.7 (P = 0.059)	NS	NS
(8) Difficulty working	64	46	42	5.5 (P = 0.06)	NS	NS

Three group comparisons of the number of “yes” responses for the questions in the comfort and activity surveys. Questions are listed under their respective survey, Comfort or Activity. Groups were abbreviated as T (tetra), P (para), and C (control). The Chi-Square column is the result of 3-group chi-square analysis (3 × 2 contingency table) with α level of 0.05. Asterisks in the Tetra, Para, and Control columns indicate a statistically significant difference from the null hypothesis (observed = expected). The Observed vs. Expected column reflects the result of standardized residual analysis with Bonferroni adjusted p values (Bonferroni correction for 6 comparisons). Pairwise comparisons utilized 2 × 2 chi-square contingency tables with Bonferroni adjusted p values (Bonferroni correction for 3 comparisons). NS, not significant.

Thermal activity survey

For questions that assessed the impact of seasonal warm temperatures on performance of activities, a significant overall difference in the percentages of “yes” responses existed among the three groups, when asked whether heat-related discomfort limited their ability: (1) to stay inside their home when they wanted to (24 vs. 10 vs. 8%, respectively; P = 0.043) and (2) to go outside their home when they wanted to (62 vs. 34 vs. 32%, respectively; P = 0.003). (Fig. 2; see Table 2 for results of pairwise comparisons).

Figure 2.

Percent (%) of participants in each group who responded “yes” when asked whether seasonal heat limited their ability to go outside (Thermal Activity Survey). The percentage of participants with tetraplegia who responded “yes” was significantly higher than expected, while the percentage of non-SCI controls who responded “yes” was significantly lower than expected. The percentage of “yes” responses in the tetraplegic group was significantly higher compared to the paraplegic group and control group. Dagger (†) indicates significant within-group difference compared to the null hypothesis (†† P < 0.01, † P < 0.05). Asterisk (*) indicates significant between-group comparison (*P < 0.05; **P < 0.01).

A significant overall difference in the percentages of participants who responded “yes” existed among the tetraplegic, paraplegic, and control groups when asked if during seasonal heat (3) they ever had to spray themselves with water or use a mister (70 vs. 44 vs. 42%; P = 0.008), (4) they had to wear more clothes than other people in the same indoor environment, to stay comfortable (34 vs. 22 vs. 4%; P = 0.001), (5) they had to wear more clothes than other people to stay comfortable outdoors (34 vs. 14 vs. 12%; P = 0.01); and (6) an inability to stay comfortable outdoors limited participation in their normal social activities (40 vs. 20 vs. 16%; P = 0.013) (Fig. 3; see Table 2 for results of pairwise comparisons).

Figure 3.

Percent (%) of participants in each group who responded “yes” when asked whether they needed to use a spray bottle/mister because of seasonal heat (Thermal Activity Survey). The percentage of “yes” responses in the tetraplegia group was significantly higher than expected and higher than the percentage of “yes” responses compared to the paraplegic group and control group. Dagger (†) indicates significant within-group difference compared to the null hypothesis († P < 0.05). Asterisk (*) indicates significant between-group comparison (*P < 0.05).

When asked other questions on the impact of seasonal heat on activities, the percentages of “yes” responses appeared to differ among the tetraplegic, paraplegic, and control groups. However, these comparisons did not achieve statistical significance, i.e. when asked whether heat-related discomfort (7) limited their ability to keep their scheduled physician’s appointments (26 vs. 10 vs. 12%; P = 0.059); and (8) caused work or other activities to be more difficult during the summer (64 vs. 46 vs. 42%; P = 0.06) (Table 2).

In post hoc comparisons of Hi-Para (SCI ≥ T6) vs. Lo-Para (SCI < T6) groups, the percentage of “yes” responses appeared to be higher in the Hi-Para group for both Comfort questions and most Activity questions. However, none of these comparisons were statistically different for any of the questions (Fig. 4).

Figure 4.

Between-group pairwise comparisons (Hi-Para, Lo-Para, Control) for questions 1–2 of the Thermal Comfort Survey and questions 1–6 of the Thermal Activity Survey. The percentage of “yes” responses in the Hi-Para group was significantly higher compared to the control group when asked whether they had to wear more clothes than other people in the same indoor environment, to stay comfortable. Asterisk (*) indicates significant between-group comparison (*P < 0.001).

In post hoc comparisons of Hi-Para vs. control groups, the percentage of “yes” responses appeared to be higher in the Hi-Para group for all Comfort and Activity questions. However, only question (4) having to wear more clothes than other people to stay comfortable indoors, achieved statistical significance (29.6 vs. 4%, respectively; P = 0.001) (Fig. 4).

Discussion

Our findings demonstrate that the subjective experiences of warm seasonal temperatures were different among persons with tetraplegia, paraplegia, and non-SCI controls. The responses to questions 1 and 2 of the Thermal Comfort survey demonstrated that persons with tetraplegia, once overheated, required significantly more time to cool down than persons with paraplegia and controls (Fig. 1). These persons were also more likely to experience an increased frequency of heat-induced dizziness or lightheadedness compared to non-SCI controls.

The greater cool-down time required in the tetraplegia group can be attributed to the nearly complete interruption of control of thermoregulatory mechanisms for heat dissipation after cervical SCI, resulting in greater heat storage (7). Sympathetic-mediated vasodilation and sympathetic cholinergic-mediated sweating is impaired below the NLI, which is approximately 75% of the body’s surface area in tetraplegia as compared to ∼60% in high paraplegia (≥T6) and <50% in low paraplegia (<T6) (12, 20–22). Impaired cutaneous vasodilation limits the ability to increase delivery of warm blood from the core to the skin for heat loss through radiation (11). As ambient temperatures increase from warm to hot, the loss of the ability to sweat from a large percentage of the body’s surface area becomes more disruptive on altering the balance of heat storage to heat loss, causing persons with tetraplegia to be more affected than persons with paraplegia and controls, even while at rest (7, 23). Our sub-analysis suggests that the Hi-Para group responded more similarly to the tetraplegia group, while the Lo-Para group appeared to respond more similarly to controls. As such, during seasonal heat exposure, persons with tetraplegia and high paraplegia would have the greatest increase in heat storage and would require a longer period to dissipate that heat due to their limited heat dissipating mechanisms. With more complete neurological injuries, the lower extremities would be significant contributors to the increased heat storage due to greater skeletal muscle paralysis, sensory loss, circulatory impairment, and vascular atrophy below the NLI (24).

Although Tcore values were not recorded, the significantly higher frequency of “yes” responses for feeling dizzy or lightheaded during the warm seasons in the tetraplegic group compared to the control group was most likely due to persons with higher SCI having varying degrees of hyperthermia (25).

Investigations in non-SCI persons have shown that hyperthermia can impair executive function and short-term memory (26, 27). In persons with SCI, Tcore lability predicted the degree of sympathetic interruption and cognitive performance during heat exposure with higher levels of SCI associated with greater lability of Tcore (28). The greater degree of sympathetic interruption and thermoregulatory dysfunction in persons with tetraplegia would allow Tcore to approach the range of hyperthermia (≥38°C) faster than controls (29). A Tcore greater than 38°C would most likely be accompanied by feeling dizzy, a deterioration in cognitive impairment, and other adverse signs and symptoms of hyperthermia (25, 30).

For the Thermal Activity survey, the responses to question 1 (staying indoors when you want to) were different among the three groups. Although not significantly different, it appeared that persons with tetraplegia may have felt the least comfortable indoors, during the warmer seasons, among the groups.

For questions 2 and 3 (do warm seasonal temperatures present a barrier to going outdoors and do you need to use a water-mister), the frequency of “yes” responses was greater in persons with tetraplegia compared to those with paraplegia and controls (Figs. 2 and 3). The interruption of vasodilation and sweating in 75% of the body’s surface area, as discussed above, would account for the differences in questions 1–3 (7, 11, 12, 23).

For question 4 (wearing more clothes than others indoors), both persons with tetraplegia and paraplegia responded “yes” more frequently than controls. Our sub-analysis revealed that persons with high paraplegia responded “yes” more frequently than controls, appeared to respond “yes” more frequently than persons with low paraplegia, while responses of persons with low paraplegia were not different than controls (Fig. 4). Although counter-intuitive during the warm seasons, these reported findings are supported by objective findings of significantly lower Tcore in persons with tetraplegia and high paraplegia compared to non-SCI controls despite ambient temperatures being thermoneutral (28, 29, 31). The lower Tcore may be attributed to impaired vasomotor control below the NLI and less skeletal muscle mass available for thermogenesis in persons with high-level SCI, leaving them in a chronic state of vasodilation, causing uncontrolled heat loss (22, 31, 32). Since indoor ambient temperatures may be cooler than outdoor temperatures and persons are usually less active indoors, wearing more clothes than non-SCI controls may increase body heat preservation and thermal comfort. However, when outdoors during warmer seasons, only persons with tetraplegia reported wearing more clothes than the other two groups. We speculate that once outdoors, persons with paraplegia are more likely to engage more skeletal muscle mass during physical activities, produce more body heat than persons with tetraplegia, and decrease their reliance on passive insulation from additional clothing.

For questions 7 and 8 (do warm seasonal temperatures become a barrier to maintaining physician appointments and make work more difficult), it appeared that the frequencies of “yes” responses were higher in the tetraplegic group. This difference would seem reasonable due to the proposed reluctance to venture outdoors on hot days and the increased likelihood of incurring the negative impact of hyperthermia on cognition and comfort in the tetraplegic group with prolonged exposure. However, once corrected for multiple between-group comparisons, the P-value failed to reach statistical significance.

Post hoc, within-paraplegia-group comparisons of “yes” responses in the Hi-Para (n = 27) vs. Lo-Para (n = 23) sub-groups, appeared to be higher in the Hi-Para group for all questions except Activity question 6 (inability to stay comfortable limited participation in outdoor social activities). However, none of these comparisons were significantly different (Fig. 4). Although not different, the comparisons in Comfort questions 1–2 and Activity questions 1–5 seem physiologically sound due to the reduced skin surface area available for heat dissipation in the Hi-Para group (∼60%) vs. Lo-Para group (<50%), resulting in greater disruption of heat storage/heat loss balance in the Hi-Para group (12).

When comparing Hi-Para to controls, the percentage of “yes” responses appeared to be higher in the Hi-Para group for all questions, although most were not significantly different except for question 4 (wearing more clothes than other people to stay comfortable indoors), which achieved statistical significance (P = 0.001) (Fig. 4). These comparisons seem plausible and support the greater vulnerability of persons with higher levels of SCI (≥T6) to the adverse effects of hyperthermia (11, 12).

Our sub-analyses (Hi-Para vs. Lo-Para, Hi-Para vs. Control) seem to show that responses of the Hi-Para group were closer to the tetraplegia group, while responses of the Lo-Para group were closer to the controls. This meaningful trend is supported by evidence of greater vasomotor impairment (causing uncontrolled heat loss) in persons with high paraplegia, greater impairment of evaporative heat loss, and less innervated skeletal muscle for heat production than persons with low paraplegia or controls (11, 12, 23).

Limitations

As mentioned, survey questions were constructed from the most frequent complaints our investigators received from research participants in prior studies conducted during the warmer seasons. Although the final questions were reviewed by participants, medical providers, and research staff with SCI for construct validity, the survey questions were not validated.

No objective data were recorded. Therefore, interpretation of statistically significant between-group differences in “yes” responses to the negative impact of warmer seasonal temperatures on comfort and activity were based on accepted pathophysiology from previous investigations in persons with SCI. Knowledge of each participant’s Tcore, degree of autonomic impairment, e.g. ability to vasodilate and sweat and International Standards to document Autonomic Function following SCI (ISAFSCI) score, would have improved our understanding of the pathophysiology responsible for our findings and, hence, conclusions.

Dividing the paraplegia group into Hi-Para (n = 27) and Lo-Para (n = 23) limited the statistical power of those post hoc comparisons.

The study was open to all persons with SCI who satisfied the study’s inclusion/exclusion criteria. Participants were recruited through advertising, physician referral, and word of mouth. As several of our participants were known to the investigators or medical staff of the James J. Peters Veterans Affairs Medical Center or the Kessler Foundation, our sampling method was closer to convenience sampling than that of random sampling.

Conclusion

During the warmer seasons, persons with tetraplegia reported more discomfort from heat exposure than controls and required more time to cool down and regain comfort than either persons with paraplegia or controls. Persons with tetraplegia reported that warm seasonal temperatures presented a barrier to venturing outdoors and reported a greater frequency of reliance on water misters to cope with heat exposure compared to persons with paraplegia or controls. The warmer seasons also limited participation in outdoor social activities to a greater extent in persons with tetraplegia than controls. The greater interruption of thermoregulatory mechanisms for heat dissipation in persons with tetraplegia may be assumed to be the underlying mechanism for these findings. Persons with tetraplegia and paraplegia reported wearing more clothes indoors to stay comfortable than controls in similar environments, with the responses of those with high paraplegia driving the between-group difference. This difference demonstrates the impact of thermodysregulation in indoor as well as outdoor environments and that its negative impact is greater in persons with high paraplegia than persons with low paraplegia. Researchers and clinicians should realize that the risk level for thermodysregulation is not the same for all persons with paraplegia and should be stratified according to a more clinically relevant classification of high or low paraplegia.

Further research is needed to validate our thermal survey and to develop a validated survey tool to assess the impact of thermodysregulation on QOL, which can be utilized with other validated survey tools for persons with SCI. Such a survey tool may be applied to assess meaningful change in QOL, when testing interventions designed to address autonomic dysregulation after SCI, such as those of spinal cord stimulation and bioengineering interventions (e.g. powered, self-regulating heating and cooling garments).

Disclaimer statements

Contributors None.

Funding Funding This study was supported by the Veterans Affairs Rehabilitation Research & Development Service, National Center for the Medical Consequences of Spinal Cord Injury (#B-2020C). We also wish to thank the James J. Peters Veterans Affairs Medical Center, Bronx, NY for their support.

Conflicts of interest No potential conflict of interest was reported by the author(s).