Background
Excessive daytime sleepiness (EDS) is a common problem in various populations [
1‐
5]. It has been associated with age [
3,
5], sex [
5‐
7], body mass index (BMI) [
8‐
10], shift work [
11], snoring [
12‐
14], comorbidities [
15], social conditions [
5,
16] and obstructive sleep apnea [
2,
17,
18]. Deleterious outcomes of EDS include poor work performance [
19], motor vehicles accidents [
20,
21], and work injuries [
22,
23]. We have recently observed EDS prevalence of 15.9% to 20.8% in Caucasian populations in rural Saskatchewan [
5,
24]. High rates of EDS have been documented in New Zealand Maori Indigenous populations (21.3%) compared to New Zealand non-Maori populations (13.9%) [
25]. Knowledge is limited for First Nations populations.
First Nations people in Canada characteristically have high rates of respiratory morbidities, including asthma and chronic obstructive pulmonary disease (COPD) [
26‐
30]. Among First Nations people living on reserves in Canada, 59% engaged in non-traditional use of tobacco (smoking) [
31]. Age standardized hospital separation rates in Western Canada for Indigenous people for all respiratory diseases in 2000 were high at 3040/100,000 compared to 920/100,000 in the general population [
27].
First Nations populations in Canada are characterized by disadvantaged socio-economic status [
32]. The average annual income in 2010 was $18,586 for on-reserve First Nations people compared to $41,052 for other Canadians [
32]. Twenty-eight percent of on-reserve First Nations persons live in crowded housing conditions of more than one person per room, compared to 4% of non-Indigenous persons in Canada [
33]. Forty-three percent of persons living on-reserves had homes in need of major repairs [
33]. Poor housing conditions are associated with dampness and mold which may be associated with deleterious respiratory outcomes [
27].
In Canada, the term commonly used to refer to people registered under the Indian Act is “First Nations” [
34]. There is limited information on EDS among First Nations people in Canada [
35]. In 2011, of the 1,033,381 persons in Saskatchewan, 103,205 were First Nations [
36]. The objective of this study was to identify the prevalence of EDS and to investigate factors contributing to EDS among adult First Nations people living in two reserve communities in rural Saskatchewan.
Results
The mean (±SD) age of the 408 men who participated was 33.7 (±13.9) years and of the 421 women was 35.9 (±14.4) years. Fifty percent had completed high school (Grade 12). Twenty-nine percent were overweight and 35% were obese. Non-traditional use of tobacco (current smoking) was present in 78.3%, ex-smoking in 12.2%, and never smoking in 9.5% persons. Loud snoring was reported by 17.0% men and 14.8% women. There were 91 (11.0%) adults with an ESS score > 10. More women (12.4%) than men (9.6%) had ESS scores >10.
As shown in Table
1, unadjusted univariate analysis showed that older age [>55 years of age, OR 4.46 (95% CI 2.34 to 8.52)] was significantly associated with high ESS score. With regard to doctor diagnosed conditions significantly associated with the risk of having high ESS scores included: sinus trouble [OR 2.24 (95% CI 1.42 to 3.54)], heart problems [OR 2.55 (95% CI 1.47 to 4.41)], tuberculosis [OR 2.71 (95% CI 1.30 to 5.63)], attack of bronchitis [OR 2.22 (95% CI 1.38 to 3.56)], chronic lung disease [OR 2.35 (95% CI 1.51 to 3.64)], and SOB [OR 3.15 (95% CI 1.92 to 5.18)]. Loud snoring [OR 1.68 (95% CI 1.02 to 2.77)] was also associated with high ESS scores. House in need of repairs and crowding (more than one person per room) were significant at
p < 0.2 and hence included in the multivariate model as potential confounders.
Table 1
Univariate associations between ESS score > 10 and independent variables of interesta
Demographics | | | |
Sex | | | |
Female (reference) | 369 (87.6) | 52 (12.4) | 1.00 |
Male | 369 (90.4) | 39 (9.6) | 0.76 (0.48–1.20) |
Age, in years | | | |
17–25 (reference) | 266 (92.7) | 21 (7.3) | 1.00 |
26–35 | 180 (88.2) | 24 (11.8) | 1.71 (0.90–3.26) |
36–45 | 119 (89.5) | 14 (10.5) | 1.45 (0.69–3.03) |
46–55 | 113 (91.1) | 11 (8.9) | 1.30 (0.58–2.90) |
> 55 |
60 (74.1)
|
21 (25.9)
|
4.46 (2.34–8.52)
|
Educational level | | | |
Completed postsecondary education (reference) | 103 (88.8) | 13 (11.2) | 1.00 |
Completed university | 89 (88.1) | 12 (11.9) | 1.02 (0.41–2.53) |
Completed high school | 191 (92.7) | 15 (7.3) | 0.61 (0.26–1.43) |
Less than high school | 354 (87.6) | 50 (12.4) | 1.12 (0.56–2.25) |
Marital status | | | |
Widowed/divorced/separated/single (reference) | 430 (88.5) | 56 (11.5) | 1.00 |
Married/common in law | 288 (89.4) | 34 (10.6) | 0.88 (0.56–1.38) |
Body mass index, kg/m2
| | | |
Normal (<25) (reference) | 251 (90.0) | 28 (10.0) | 1.00 |
Overweight (25–29.9) | 213 (88.4) | 28 (11.6) | 1.14 (0.64–2.05) |
Obese (≥30) | 258 (88.4) | 34 (11.6) | 1.15 (0.68–1.95) |
Smoke status | | | |
Non-smoker (reference) | 68 (86.1) | 11 (13.9) | 1.00 |
Ex-smoker | 85 (84.2) | 16 (15.8) | 1.27 (0.51–3.16) |
Current smoker | 585 (90.1) | 64 (9.9) | 0.72 (0.36–1.42) |
In past 12 months, had ≥5 drinks on one occasion | | | |
No (reference) | 156 (88.1) | 21 (11.9) | 1.00 |
Yes | 579 (89.6) | 67 (10.4) | 0.84 (0.50–1.41) |
Employment status | | | |
Yes (reference) | 388 (89.2) | 47 (10.8) | 1.00 |
No | 346 (88.7) | 44 (11.3) | 1.05 (0.67–1.64) |
Doctor ever diagnosed: | | | |
Sinus trouble | | | |
No (reference) | 470 (91.8) | 42 (8.2) | 1.00 |
Yes |
189 (83.3)
|
38 (16.7)
|
2.24 (1.42–3.54)
|
Heart problem | | | |
No (reference) | 674 (90.2) | 73 (9.8) | 1.00 |
Yes |
62 (78.5)
|
17 (21.5)
|
2.55 (1.47–4.41)
|
Tuberculosis | | | |
No (reference) | 597 (90.5) | 63 (9.5) | 1.00 |
Yes |
43 (78.2)
|
12 (21.8)
|
2.71 (1.30–5.63)
|
Attack of bronchitis | | | |
No (reference) | 466 (91.6) | 43 (8.4) | 1.00 |
Yes |
180 (82.9)
|
37 (17.1)
|
2.22 (1.38–3.56)
|
Ever had asthma | | | |
No (reference) | 616 (89.3) | 74 (10.7) | 1.00 |
Yes | 122 (87.8) | 17 (12.2) | 1.12 (0.64–1.95) |
Questionnaire ascertained conditions | | | |
Chronic Lung Diseaseb
| | | |
No (reference) | 554 (91.6) | 51 (8.4) | 1.00 |
Yes |
184 (82.1)
|
40 (17.9)
|
2.35 (1.51–3.64)
|
SOB | | | |
No (reference) | 367 (94.3) | 22 (5.7) | 1.00 |
Yes |
365 (84.1)
|
69 (15.9)
|
3.15 (1.92–5.18)
|
Loud snoring | | | |
No (reference) | 626 (89.9) | 70 (10.1) | 1.00 |
Yes |
110 (84.0)
|
21 (16.0)
|
1.68 (1.02–2.77)
|
Socio-economic Status | | | |
Money left over at end of the month | | | |
Some (reference) | 188 (86.2) | 30 (13.8) | 1.00 |
Just enough | 171 (90.5) | 18 (9.5) | 0.64 (0.34–1.22) |
Not enough | 340 (90.2) | 37 (9.8) | 0.65 (0.37–1.15) |
Annual household income | | | |
$20,000 and over (reference) | 199 (91.7) | 18 (8.3) | 1.00 |
$10,000–$19,999 | 106 (86.9) | 16 (13.1) | 1.58 (0.76–3.27) |
Less than $10,000 | 188 (85.8) | 31 (14.2) | 1.75 (0.88–3.47) |
Refusal/not stated | 245 (90.4) | 26 (9.6) | 1.09 (0.54–2.19) |
Home need repairing | | | |
No (reference) | 205 (89.5) | 24 (10.5) | 1.00 |
Minor | 188 (85.1) | 33 (14.9) | 1.51 (0.82–2.80) |
Major | 188 (85.1) | 28 (8.7) | 0.81 (0.46–1.43) |
Home crowded status (person per room) | | | |
one or less person per room (reference) | 188 (85.1) | 52 (9.7) | 1.00 |
More than one person per room | 215 (86.3) | 34 (13.7) | 1.44 (0.88-2.36) |
Multivariable logistic regression analysis (Table
2) indicated a trend towards statistical significance for age greater than 55 years [OR 2.27 (95% CI 0.94 to 5.52);
p = 0.07]. Doctor ever diagnosed tuberculosis [OR 3.02 (95% CI 1.32 to 6.87)] was significantly related to high ESS. Chronic lung disease [OR 2.01 (95% CI 1.15 to 3.50)] and SOB [OR 2.76 (95% CI 1.52 to 4.99)] were significantly related to high ESS scores. Loud snoring [OR 2.21 (95% CI 1.13 to 4.33)] continued to be an associated condition. Socio-economic factors of low income [OR 2.59 (95% CI 1.20 to 5.60)], house in need of repairs [OR 2.40 (95% CI 1.18 to 4.87)] and more than one person per room [OR 2.07 (95% CI 1.16 to 3.69)] were significantly associated with high ESS scores. There were no associations for BMI and smoking with high ESS scores.
Table 2
Multivariable logistic regression of the association between ESS score > 10 and independent variables of interest
Sex | | |
Female (reference) | 1.00 | |
Male | 0.67 (0.36–1.22) | 0.189 |
Age, in years | | |
17–25 (reference) | 1.00 | |
26–35 | 2.06 (0.98–4.35) | 0.057 |
36–45 | 1.17 (0.49–2.82) | 0.722 |
46–55 | 0.84 (0.34–2.07) | 0.709 |
> 55 | 2.27 (0.94–5.52) | 0.070 |
Body mass index, kg/m2 | | |
Normal (<25) (reference) | 1.00 | |
Overweight (25–29.9) | 0.75 (0.38–1.49) | 0.409 |
Obese (> = 30) | 0.49 (0.23–1.03) | 0.061 |
Smoke status | | |
Non-smoker (reference) | 1.00 | |
Ex-smoker | 1.37 (0.44–4.24) | 0.586 |
Current smoker | 0.52 (0.21–1.29) | 0.159 |
Tuberculosis | | |
No (reference) | 1.00 | |
Yes |
3.02 (1.32–6.87)
|
0.009
|
Chronic Lung Disease | | |
No (reference) | 1.00 | |
Yes |
2.01 (1.15–3.50)
|
0.014
|
Shortness of breath | | |
No (reference) | 1.00 | |
Yes |
2.76 (1.52–4.99)
|
0.001
|
Loud snoring | | |
No (reference) | 1.00 | |
Yes |
2.21 (1.13–4.33)
|
0.021
|
Annual household income | | |
More than $20,000 (reference) | 1.00 | |
$10,000–$19,999 | 1.93 (0.84–4.41) | 0.119 |
Less than $10,000 |
2.59 (1.20–5.60)
|
0.016
|
Refusal/not stated | 1.37 (0.61–3.08) | 0.450 |
Home need repairing | | |
No (reference) | 1.00 | |
Minor |
2.40 (1.18–4.87)
|
0.015
|
Major | 0.90 (0.47–1.75) | 0.766 |
Home crowded status (person per room) | | |
one or less person per room (reference) | 1.00 | |
More than one person per room |
2.07 (1.16–3.69)
|
0.014
|
Discussion
The findings from this study highlight the strong associations of certain respiratory co-morbidities, indicators of poverty and snoring with EDS among people living on two on-reserve First Nation communities in the Province of Saskatchewan in Canada.
In addition, annual household income (less than $10,000 per year), houses in need of repairs, and over-crowding, all indicators of social determinants of health consistent with poverty [
42‐
44] were associated with high ESS scores. The relationship of poverty to sleep disturbance has been described for non-Indigenous populations [
45‐
47]. Social determinants of health of which low socio-economic status is one, are associated with co-morbidities [
48‐
50]. Respiratory co-morbidities associated with EDS in the present study were doctor ever diagnosed tuberculosis, reported chronic lung disease, and SOB. The significant relationship between SOB and EDS in our study is consistent with the observations of Kaneita et al. [
51] The association between EDS and chronic lung disease in our study is consistent with the findings of Karachaliou et al. [
52] and Koutsourelakis et al. [
53] We did not find reports linking past tuberculosis with high ESS score. However, chronic lung disease has been observed in former tuberculosis patients [
54], and it is possible that the apparent relationship between past tuberculosis and high ESS score in our study is as a result of chronic lung disease in former tuberculosis patients.
In the univariate analysis, older age (≥55 years of age) was associated with high ESS score. In the multivariate analysis borderline significance for age persisted. Increasing age is recognized as being associated with increased risk for EDS [
3,
5]. The prevalence of high ESS scores in this fairly young population (men 33.7 years, women 35.9 years) that we studied was 11.0%. The prevalence of high ESS score (25.9%) in the oldest (>55 year) age group was higher than in the non-Indigenous population (18.5%) of rural Saskatchewan described by Gjevre et al. [
5], and more like that described by Paine et al. for the Maori population (21.3%) in New Zealand [
25].
Obesity has been identified as an independent predictor of EDS in both men and women.
9, [
55,
56] However, in our study the effect of overweight and obesity on high ESS scores was not statistically significant, likely due to lack of variability with 64% of the population being either overweight or obese. Following discussion with the communities, the high percentage of obesity can be addressed in future by the introduction of healthier eating and exercise programs.
The significance of EDS for the health of the populations participated is important to consider. EDS is a hallmark feature of obstructive sleep apnea [
2,
17,
18]. Among those with high ESS scores in the populations that we studied, there may be a high prevalence of undiagnosed and untreated sleep disordered breathing with all of the implications for cardiovascular outcomes [
57,
58] and accidents [
22,
59,
60].
Mechanisms by which these factors might affect EDS merit discussion. We have shown that socio-economic factors relate to respiratory status in rural people [
61]. Respiratory co-morbidities may enhance EDS [
62] and/or upper airway instability leading to sleep disordered breathing [
63] and concomitant EDS [
64]. It has been demonstrated that environmental exposures are associated with increased sleep disordered breathing, possibly because of enhanced upper airway inflammation [
65]. Our results show that homes requiring repairs are associated with high ESS scores. It is possible that endotoxin or mold exposure associated with dampness in these homes could result in upper airway inflammation [
66,
67] thus acting by a similar mechanism. Cigarette smoking may enhance OSA [
68] with consequent increased EDS. But like our finding for BMI, smoking was not a significant contributor to EDS, likely because smoking was highly prevalent in the population (78.3% current smokers; 12.2% ex-smokers). The high prevalence of non-traditional use of tobacco (smoking) is being address by a community-chosen intervention called the “Green Light Program”. The Green Light Program is an evidence-informed, community-level intervention which identifies and celebrates homes that are smoke-free. Currently, in excess of 50% of the homes in both communities are smoke-free.
Certain strengths and limitations apply to our study. Strengths include the size of the populations studied, and the consistently strong of associations with respiratory co-morbidities, indices of social determinants of health, and snoring. This study adds to a small but growing body of knowledge on sleep issues affecting Indigenous populations. A major limitation is the recall-bias of medical history due to the cross-sectional nature of the study. One of other limitations is information bias due to conducting the study in First Nation communities. That is, we hired local people to conduct the interviews and closeness among community members could lead to information bias. Response rates for household surveys and individual surveys in Community A were lower compared to Community B. Compared to Community B, Community A is spread over a much wider area of land resulting in lower response rates due to difficulties in access to the health clinic [
37]. Other potential limitation of the study is the lack of validation of the ESS in First Nations people. While all the younger people in this study spoke English, on site interpretation was required for some of the older participants. It is possible that the ESS may be a culturally sensitive tool [
69], with potential observer bias when used in non-Caucasian cultures.
Acknowledgements
We are grateful for the contributions of Elders, community leaders that facilitated the engagement necessary for the study, and all individuals who donated their time to participate. The First Nations Lung Health Project was funded by a grant from the Canadian Institutes of Health Research “Assess, Redress, Re-assess: Addressing Disparities in Respiratory Health among First Nations People”, CIHR MOP-246983-ABH-CCAA-11829. The team consists of: James Dosman, MD (Designated Principal Investigator, University of Saskatchewan, Saskatoon, SK Canada); Punam Pahwa, PhD (Co-Principal Investigator, University of Saskatchewan, Saskatoon SK Canada); Late Jo-Ann Episkenew, PhD (Co-Principal Investigator), Former Director of Indigenous People’s Health Research Centre, University of Regina, SK Canada), Sylvia Abonyi, PhD (Co-Principal Investigator, University of Saskatchewan, Saskatoon, SK Canada); Co-Investigators: Mark Fenton, MD, Bonnie Janzen, PhD, Chandima Karunanayake, PhD, Malcolm King, PhD, Shelly Kirychuk, PhD, Niels Koehncke, MD, Joshua Lawson, PhD, Greg Marchildon, PhD, Lesley McBain, PhD, Donna Rennie, PhD, Vivian R Ramsden, RN, PhD, Ambikaipakan Senthilselvan, PhD; Collaborators: Amy Zarzeczny, BA, LLM; Louise Hagel, MSc, Breanna Davis, MD, John Dosman, MD, Roland Dyck, MD, Thomas Smith-Windsor, MD, William Albritton, MD, PhD; External Advisor: Janet Smylie, MD, MPH; Project Manager: Kathleen McMullin, MEd; Community Partners: Jeremy Seeseequasis, BA; Laurie Jimmy, RN; Judith Macdonald, RN, BScN; Arnold Naytowhow.