Increased Participation in Activities of Daily Living Is Associated With Lower Cholesterol Levels in People With Spinal Cord Injury

Article Outline

• Abstract
• Methods
  • Participants
  • Activities of Daily Living
  • Biometric Data
  • Data Screening
  • Statistical Analyses
• Results
  • Covariates
  • Activities of Daily Living Participation
  • Biometric Data
  • Total Activities of Daily Living
  • Mobility Activities of Daily Living
  • Domestic Activities of Daily Living
• Discussion
  • Study Limitations
• Conclusions
• Acknowledgments
• References
• Copyright

Abstract 

Hetz SP, Latimer AE, Martin Ginis KA, Buchholz AC, and the SHAPE-SCI Research Group. Increased participation in activities of daily living is associated with lower cholesterol levels in people with spinal cord injury.

Objective

To evaluate the relationships between activities of daily living (ADLs) participation and coronary heart disease (CHD) risk factors in people with spinal cord injury.

Design

Cross-sectional.

Setting

Community, university, hospital.

Participants

Participants (N=75) from the Study of Health and Activity in People With Spinal Cord Injury study (61 men, 14 women).

Interventions

Not applicable.

Main Outcome Measures

Physical Activity Recall Assessment for People With Spinal Cord Injury and CHD risk factor assessment including waist circumference, total cholesterol, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol, and triglycerides.

Results

Using generalized linear models, and controlling for leisure time physical activity and covariates, increased Mobility ADLs (transferring and wheeling) were associated with lower plasma total cholesterol and LDL. No other significant relationships emerged.

Conclusions

Mobility ADLs were associated with lower total cholesterol and LDL. However, neither Total ADLs nor Domestic ADLs were associated with CHD risk. Further investigation is needed to determine causality between Mobility ADLs and CHD risk.

Key Words: Activities of daily living, Coronary heart disease, Rehabilitation, Spinal cord injuries

List of Abbreviations: ADLs, activities of daily living, CHD, coronary heart disease, GLM, generalized linear models, HDL, high-density lipoprotein cholesterol, LDL, low-density lipoprotein cholesterol, LPL, lipoprotein lipase, LTPA, leisure time physical activity, NEAT, nonexercise activity thermogenesis, PARA-SCI, Physical Activity Recall Assessment for People With Spinal Cord Injury, SCI, spinal cord injury, SHAPE-SCI, Study of Health and Activity in People With Spinal Cord Injury

TOTAL DAILY ENERGY expenditure is greatly attenuated in people with long-standing SCI. This decrease in energy expenditure is mainly attributed to a decrease in metabolically active fat-free mass¹ as well as a decrease in physical activity.² Not surprisingly, decreased energy expenditure in people with SCI is paralleled by elevated levels of adiposity and CHD.³ Moreover, those with SCI have a higher prevalence of obesity and CHD when compared with able-bodied counterparts.⁴ However, participation in LTPA such as resistance and aerobic training has been shown to be efficacious at lowering CHD risk factors in those with long-standing SCI.⁵

Similar to LTPA participation, ADLs (normal day-to-day fundamental tasks that are essential to everyday life, such as mobility and domestic-related activities) have been suggested to play a significant role in total daily energy expenditure.⁶ ADLs often account for the greatest proportion of activity-related energy expenditure throughout the day.⁶ Despite being brief in duration, the cumulative effects of repeated bouts of ADLs can have a very large effect on total energy expenditure.⁷ In the able-bodied population, obesity is associated with lower levels of non-exercise-related activities such as ADLs.⁸, ⁹

In addition, lifestyle physical activity programs that include ADLs (ie, accumulating activity in small bouts throughout the day) have demonstrated positive effects such as decreased adiposity similar to structured exercise interventions.¹⁰ In the SCI population, the benefits of ADLs participation are unclear. It remains to be determined whether ADLs participation, independent of LTPA, is associated with decreased CHD risk factors. Therefore, the primary purpose of this study was to examine the relationships between total daily ADLs participation (Total ADLs) and CHD risk factors including waist circumference, total cholesterol, LDL, HDL, and triglycerides in the SCI population.

Within the SCI population, ADLs, including personal care, domestic, and mobility activities, constitute approximately 90% of all physical activity during the day.¹¹ Each ADL is often performed for a longer duration,¹² is more strenuous, and elicits a higher heart rate than for an able-bodied person.¹³ There is wide variation in the physical demands of various types of ADLs. ADLs that require larger and more sustained muscle contractions (eg, mobility activities such as transferring) appear to elicit greater heart rate responses than less demanding ADLs such as personal care activites.¹³ Given the physical demands of strenuous ADLs, it is likely that these activities are associated with reduced risk of CHD. Conversely, many ADLs such as desk and office work and personal care activities are sedentary and are likely to have a weak or positive relationship with CHD risk factors.¹⁴ In turn, these weak or positive relationships are likely to offset any significant negative relationships between more rigorous ADLs such as mobility-related activities and CHD risk factors during statistical analyses. Given this variation in ADLs patterns, we hypothesized that Total ADLs participation would be unrelated to CHD risk factors.

As a secondary objective, we examined the relationships between Mobility and Domestic ADLs, and CHD risk factors. We focused on these 2 types of activities because they are often the most physically demanding ADLs for those with SCI¹³ and have been suggested to constitute the majority of ADLs throughout the day.¹⁵ Thus, we hypothesized that Mobility and Domestic ADLs categories would demonstrate negative relationships with CHD risk factors.

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Methods 

This study involved an analysis of 75 people who participated in the SHAPE-SCI.¹⁶ Participants completed the PARA-SCI as well as a biometric evaluation consisting of venous blood sampling and waist circumference measurements. All biometric data were collected within 14 days of the PARA-SCI in the participants' homes.

Participants 

The sample size was limited to those who had completed a biometric evaluation for cardiovascular disease risk factors. A full list of measurements as well as inclusion and exclusion criteria for the SHAPE-SCI are reported elsewhere.¹⁶ Briefly, study inclusion criteria included the following: (1) traumatic SCI etiology, (2) 18 years of age or older, (3) assistance required for mobility (manual or power wheelchair, walker, braces, cane), (4) SCI years postinjury of more than 12 months, (5) proficient in reading and speaking English, (6) reside within 200km of McMaster University, (7) able to transfer themselves with assistance between wheelchair and bed, and (8) no cognitive or memory impairments. Participant demographic characteristics are presented in table 1. All applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during the course of this research.

Table 1. Participant Demographic Characteristics

Characteristic	Value
Age (y)	42.39±11.78⁎
Years postinjury†	14.94±10.57⁎
Sex
Men	61(81.3%)
Women	14(18.7%)
Level of injury
Paraplegia	38(50.7%)
Tetraplegia	37(50.3%)
Type of mobility
Manual wheelchair	53(71.6%)
Power wheelchair	17(23.0%)
Ambulate	4(5.4%)
Marital status
Single	41(54.7%)
Married/common law	34(45.3%)

NOTE. N=75; data are expressed as n (%) unless otherwise indicated.

Activities of Daily Living 

The PARA-SCI¹⁷ is a self-report measure of all activities performed over a 3-day recall period. The PARA-SCI is administered via telephone using a consistent and structured interview protocol. Participants reported the specific activity, duration, and intensity of both ADLs and LTPA according to the PARA-SCI guidelines. Consistent with the PARA-SCI protocol (Martin Ginis KA, Latimer AE, PARA-SCI Administration and Scoring Manual [Hamilton, ON: McMaster University, 2008]), activities reported to require no physical effort were not recorded. Specific ADLs scores for each activity were calculated by summing the time spent engaged in mild-, moderate-, and heavy-intensity ADLs. The detailed definitions of these intensity levels have been reported elsewhere.¹⁷ In addition to providing a better representation of ADLs participation, combining the 3 intensity levels also increased statistical power by limiting the number of subsequent models and decreased the likelihood of a type I error. The ADLs component of the PARA-SCI has demonstrated reliability¹⁵ and validity.¹¹ ADLs scores from the PARA-SCI are associated with fitness level (maximum oxygen consumption) and differentiate between injury level.¹⁵

Similar to past analyses that used PARA-SCI ADLs scores,¹⁵ activities that required similar functional movements were clustered. For example, activities involving personal care (eg, washing face, brushing teeth, and brushing hair) were clustered into the grooming category. Clustering the activities was essential for further analysis because most individually reported ADLs (eg, brushing hair) had minimal participation.

Wheeling and transferring were combined into the Mobility ADLs class, and cleaning, food preparation, laundry, and yard work were combined into the Domestic ADLs class. This further categorization helped to increase statistical power and provides more generalizable information regarding a class of activities (eg, mobility and domestic activities) rather than specific activities (eg, mopping the floor).

Although very sedentary activities such as desk and office work and personal care activities were included in Total ADLs analyses, they were excluded from further analyses because they are more similar to sedentary sitting than to physical activity. Furthermore, increased time spent involved in personal care activities (grooming, bathing, and toileting) often involves assistance from a personal support worker or family member. Therefore, increased participation in personal care ADLs may be indicative of physical disability rather than increased physical activity.

Biometric Data 

As described elsewhere,¹⁸ venous blood was extracted from a forearm vein and collected into empty Vacutainer tubes. The samples were stored on ice after being collected and were transported to the laboratory for analysis on the same day (McMaster Medical Center, Department of Laboratory Medicine). Blood was centrifuged for 15 minutes at 3000 revolutions per minute before chemical analysis. HDL, total cholesterol, and triglycerides were quantified by means of a homogeneous enzymatic colorimetric test (Roche Modular ISE 1800^a). LDL was quantified indirectly by the Friedewald equation.¹⁹ Waist circumference was measured around the lowest rib in centimeters to the nearest decimal place with a nonelastic, flexible measuring tape.²⁰ Waist circumference was measured while the participants were supine with arms abducted 30° from midline and after normal expiration. Waist circumference was measured in duplicate and averaged if the difference was 5% or less; if 5% or more, a third measurement was made, and the 2 closest measurements were averaged.

Data Screening 

Seventy-five participants completed both the PARA-SCI and biometric sampling. However, 18 of these participants did not adhere to the 10-hour fasting protocol and were subsequently excluded from plasma variable analysis. Preliminary analysis revealed that the excluded participants did not differ from the included participants in demographic characteristics, biometrics, or ADLs activity (P>.05). All 75 participants were included in the waist circumference analyses.

Statistical Analyses 

Statistical analyses were performed using SPSS version 16.0.^b To identify potential covariates to include in our analysis, relationships between biometric variables and demographic characteristics such as age, years after injury, injury level, mode of mobility, and sex were examined by analysis of variance for categorical data and Pearson's bivariate 2-tailed correlations for continuous data.

GLM were used to test the relationships between biometric data and ADLs participation while controlling for LTPA and other relevant covariates. Separate GLM were used to test the relationships between each biometric indicator (eg, waist circumference, triglycerides) and ADLs. Covariates and the predictor variable (eg, Total ADLs) were entered into the model together. GLM were selected as the analysis method because it is appropriate for use with data that do not assume a normal distribution. In the GLM, normal distributions were selected for all dependent variables except for triglycerides and HDL. For these 2 variables, a gamma distribution was specified because they both demonstrated a positive skew. In addition to examining the relationships between CHD risk factors and Total ADLs participation, additional analyses were conducted to examine the relationships between CHD risk factors, Mobility ADLs, and Domestic ADLs. The remaining ADLs, although included in Total ADLs analyses, were not further evaluated because the purpose was to examine ADLs that were primarily not sedentary.

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Results 

Covariates 

Significant sex differences (P<.05) emerged for HDL (F=12.11, df=1, P=.001). Women had higher HDL levels than men. Age was positively associated with increased waist circumference (r=.34, P<.01). Finally, triglycerides were positively associated with alcohol consumption (r=.40, P<.01). These differences were controlled for in subsequent analyses. No other significant differences or associations emerged.

Activities of Daily Living Participation 

Participants spent an average of 118.81±121.29 (mean ± SD) minutes per day engaged in Total ADLs (range, 0min/d–468.83min/d). More specifically, participants spent 17.35±27.07min/d engaged in Mobility ADLs (range, 0min/d–160.03min/d), and 15.78±30.45min/d engaged in Domestic ADLs (range, 0min/d–150.00min/d). The remaining ADLs time consisted primarily of personal care and desk and office work activities.

Biometric Data 

Biometric results are reported in table 2. The relationships between ADLs participation and biometric data are reported in table 3. Each relationship was examined by using a unique GLM. Moreover, because 3 relationships were being examined for each CHD risk factor, a Bonferroni correction was used such that the P value was set at .016.

Table 2. Participant Biometric Data

Table 3. Biometric and ADL Relationships

Parameter	Total ADLs	Mobility ADLs	Domestic ADLs
HDL⁎
β	−3.32×10−5	.00	−1.60×10−5
Wald chi-square	.13	>2.28	.00
P	.72	.13	.96
LDL†
β	.00	−.005	−.002
Wald chi-square	1.40	10.96	3.30
P	.24	.001	.07
Total cholesterol†
β	.00	−.005	−.002
Wald chi-square	1.94	7.79	2.81
P	.16	.005	.09
Triglycerides‡
β	−5.35×10−5	.001	.000
Wald chi-square	.026	.44	.12
P	.87	.51	.73
Waist circumference§
β	.007	.034	.016
Wald chi-square	2.45	3.27	.93
P	.12	.07	.34

Total Activities of Daily Living 

In the models controlling for covariates and LTPA, Total ADLs participation was not related to any CHD risk factors (P>.016).

Mobility Activities of Daily Living 

In the models controlling for covariates and LTPA, more time spent engaged in Mobility ADLs was associated with lower LDL (P=.001) and with lower total cholesterol (P=.005). No significant relationships emerged between Mobility ADLs and HDL, triglycerides, or waist circumference (P>.016).

Domestic Activities of Daily Living 

In the models controlling for covariates and LTPA, Domestic ADLs participation was not related to any CHD risk factors (P>.016).

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Discussion 

It has been well established that people with SCI spend a great deal of time participating in ADLs.¹¹ However, there is limited evidence supporting the potential beneficial effects of ADLs in decreasing the risk of CHD. The current study examined the relationships between ADLs and CHD risk factors in people with chronic SCI. Interestingly, Mobility ADLs but not Total or Domestic ADLs were associated with reduced CHD risk. These findings have important implication for practice and research.

As hypothesized, Mobility ADLs were associated with lower total cholesterol and LDL. The specific physiologic mechanisms underlying the study findings are complex and poorly understood.²¹ The aerobic characteristics of Mobility ADLs may have contributed to these findings. It has been suggested that aerobic activities may be more effective than resistance training at decreasing LDL and total cholesterol.²² Interestingly, a study from the SHAPE-SCI¹⁸ that used the same data set as the one in the present study did not find significant relationships between LTPA and total cholesterol and LDL. The discrepancy between study findings indeed may be the result of the aerobic nature of Mobility ADLs²³ compared to LTPA, which often includes both aerobic and anaerobic activities (eg, resistance training).¹⁶

Another possible mechanism that should be considered is the role of LPL in LDL uptake. Physical activity, even in low amounts, has demonstrated to increase LPL activity,²⁴ which may increase the cellular uptake of LDL.²⁵ This enhancement of LPL activity may help to partially explain the negative relationships between LDL and mobility-related activity in this study. Additional research that uses a longitudinal design is needed to understand the underlying mechanisms of such processes as well as to determine causality between ADLs activity and lowered CHD risk factors.

Also in accordance with our hypotheses, Total ADLs were also unrelated to CHD risk factors. Total ADLs encompasses very sedentary activities such as desk and office work. These sedentary activities likely weakened the relationships between ADLs and CHD risk factors. Although the relationships between Domestic ADLs, and LDL and total cholesterol approached significance, we were unable to demonstrate the expected relationships between these variables. It is possible that Domestic ADLs are not performed for the same duration as the majority of Mobility ADLs. For example, ADLs wheeling may be performed extensively throughout the day as the primary mode of mobility. Furthermore, it may be that Mobility and Domestic ADLs differ in the amount of physical exertion required to accomplish these tasks.¹³ Domestic ADLs such as preparing food has been found to be much less strenuous than Mobility ADLs such as transferring into an automobile.¹³

Contrary to the hypotheses, Mobility ADLs were not associated with waist circumference and triglycerides. Short bouts of nonexercise physical activity, such as ADLs, have demonstrated to be negatively associated with waist circumference and triglycerides in able-bodied people.²⁶ Although Mobility ADLs were associated with lower LDL and total cholesterol, we were not able to demonstrate similar findings with the other biometric indicators. The inconsistencies between our study and previous research examining the relationship between short bouts of nonexercise physical activity and CHD risk factors may be due to the different measurement tools used between studies (objective vs self-report) or indicative of the sample population (able-bodied people vs people with SCI). Moreover, it is quite possible that the SCI-specific ADLs performed by the current sample were not of adequate intensity or duration to affect certain biomarkers.

Taken together, our study findings have interesting implications for future research. ADLs are often classified under an umbrella term, NEAT. NEAT has been defined as all nonexercise energy expenditures, including incidental movement, ADLs, maintenance of muscle tone and posture, fidgeting, and shivering.⁶ In the few studies conducted in the able-bodied population, lower levels of NEAT have been associated with obesity²⁷ and CHD.²⁸ NEAT has not been examined in the SCI population. Our study findings help to support the notion of the importance of considering specific components of NEAT such as Mobility ADLs when examining CHD risk factors.

By classifying and examining SCI-specific ADLs, our preliminary findings suggest that increased Mobility ADLs participation may be a strategy worth investigating as a means of decreasing CHD risk factors, particularly LDL and total cholesterol in people with SCI.

Study Limitations 

Despite extending the current literature regarding the relationships between ADLs activity and CHD risk factors, the study was limited. We expected to find a greater number of negative relationships between Mobility and Domestic ADLs, and CHD risk factors. The lack of evidence supporting these hypotheses may be indicative of the minimal amount of time participating in these ADLs classes (<18min/d). Increased participation in Mobility and Domestic ADLs, as seen in previous studies,¹⁵ may have elicited a greater number of significant negative relationships with CHD risk factors. Second, because 24% of participants did not adhere to the fasting protocol, our sample size was limited. With a small sample size and large standard deviations, the likelihood of a type II error is increased. Thus, future studies should examine these relationships; such studies should use a larger study sample and have a longitudinal design. Finally, although the PARA-SCI has demonstrated validity¹¹ and reliability,¹⁵ because of the self-reported nature of the tool, it was necessary to use subjective temporal measure (min/d) of ADLs as opposed to an objective measure such as oxygen consumption or accelerometry.

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Conclusions 

This study examined the relationships between ADLs activity and CHD risk factors among people with SCI. Mobility ADLs were associated with reduced CHD risk. Increased Mobility ADLs should be further investigated as a possible method to decrease LDL and total cholesterol levels in people with SCI.

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Acknowledgments 

We thank contributors Karen Smith, Patrick Potter, and Mary Ann McColl. We also thank Rebecca Bassett, and Iwona Chudzik for their help with data collection.

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