Highlights
Poor sleep quality is associated with a decrease in quality of life and a higher risk of suffering pathologies. Sleep hygiene habits are recommended based on their relationship with sleep quality but sometimes that intervention has no significant changes in sleep quality.
This article shows the prevalence of poor sleep quality and its association with lifestyle habits in a population recruited in community pharmacies, in Salamanca (Spain).
A real association is established between some lifestyle habits and subjective sleep quality. New strategies focused on certain habits could be developed thanks to this study.
Introduction
Disturbed sleep has been linked to cardiovascular and metabolic problems1,2 and shown to have a negative effect on mental illnesses3. Its high prevalence generates considerable costs for health systems4. In Spain, at least 20% of the population suffer symptoms of insomnia 3 nights per week, with a higher prevalence among women (23.9%) than among men (17.6%)5.
Subjective sleep quality (SQ) is the perception individuals have of how they sleep. It is based on a series of subjective evaluations by the patient and on objective sleep-related measurements. The latter include sleep latency, sleep duration, sleep efficiency, sleep disturbances, use of sleep medication and daytime dysfunction6-8. To prevent poor SQ and its consequences, strategies other than the use of medication have been investigated (cognitive behavioral therapy, sleep hygiene, etc.). In the long term, these strategies appear to be preferable to hypnotics and have demonstrated patient improvement9.
Peter Hauri coined the term “sleep hygiene” in 1977 in reference to habits, activities and practices (to encourage or avoid) that need to be considered for achieving adequate SQ10. Several studies have examined the effect of numerous lifestyle habits on improving SQ6,11-13. However, the sleep changes thus achieved are not always significant and improvement varies depending on the sleep component14-15 and age16,17.
Few studies on SQ in the population and the factors possibly associated with it have been conducted in Spain and, as far as we are aware, none has been conducted in the town of Salamanca.
The aim of this study was therefore to study the prevalence of poor SQ among the population of Salamanca and its association with specific lifestyle habits of its residents. In addition, given that many people regularly visit their community pharmacy, these establishments may be the ideal location for recruiting individuals who wish to participate in health-related studies. It is therefore of interest to see if this is the case.
Methods
Design and Participants
An observational, descriptive and cross-sectional study was carried out. It included patients over 18 years old who had visited any of 10 community pharmacies in the province of Salamanca between July and November 2019, for whatever reason. Patients who had problems communicating (language issues, deafness, speech impediments, etc.), those who had become parents in the preceding 6 months, and breastfeeding mothers were excluded from the study.
The sample was selected by means of consecutive sampling and sample size was calculated on the basis of simple random sampling, for an expected 20% prevalence of patients with poor SQ5, with a 95% confidence interval (CI95%), 5% alpha error and 5% accuracy. With these conditions, the minimum sample size required was 246 individuals. Once the minimum sample size had been achieved, patient recruitment continued until the end of the planned recruitment period.
Main Outcomes
Sleep quality (SQ): SQ was analysed using the Pittsburgh Sleep Quality Index (PSQI)18. This is a questionnaire that evaluates subjective sleep quality in patients. It comprises 24 questions, 19 of which are posed directly to patients and 5 of which are posed to the patient’s sleeping partner (the latter are not taken into account in this study). These questions shed light on 7 components of sleep quality: perceived sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbances, use of sleep medication and daytime dysfunction. These 7 components are scored from 0 (not a problem at all) to 3 (a major problem). The final PSQI score thus ranges from 0 to 21. The index furthermore has a cut-off point that classifies patients as good sleepers (PSQI≤5) or poor sleepers (PSQI>5). The questionnaire was validated in Spain by Royuela et al. and demonstrated appropriate validity and reliability. Furthermore, for classification as good or poor sleepers by means of the cut-off point, a sensitivity value of 88.63%, a specificity value of 74.19%, a positive predictive value (PPV) of 73.58% and a negative predictive value (NPV) of 88.95% were obtained19.
Lifestyle habits: participants were asked how frequently they performed specific lifestyle habits that may have a bearing on sleep quality (Table 1). Patients reply options were “Never”, “Almost never” “Sometimes”, “Almost always” and “Always”. Subsequently, frequency was labelled as “Adequate” if the activity was performed “Never” or “Almost never”, and as “Inadequate” if it was performed “Sometimes”, “Almost always” or “Always”.
Sleeping on an uncomfortable bed |
Sleeping with an uncomfortable pillow |
Correct bedroom temperature |
Bedroom too bright |
Being disturbed by something or someone while asleep |
Looking at the clock at night when unable to sleep |
Going to bed preoccupied |
Using the bed for activities other than sleeping or having sex |
Drinking coffee in the 4 hours before going to bed |
Drinking alcohol in the 4 hours before going to bed |
Going to bed hungry |
Going to bed thirsty |
Going to bed after a heavy supper |
Daytime napping lasting more than one hour during the day |
Getting up at the same time every day |
Going to bed at the same time every night |
Staying in bed after waking up |
Working in bed before going to sleep |
Taking exercise to the point of sweating in the 4 hours before going to bed |
Doing enervating activities before going to sleep |
Reading things that you consider important in bed |
Reading things that you consider trivial in bed (books, magazines, etc.) |
Texting on mobile phone in bed |
Watching TV in bed |
Listening to the radio/podcasts/music in bed |
Playing videogames during the hour before going to sleep |
Intense interaction on social media just before going to sleep |
Lightweight interaction on social media just before going to sleep |
Information was also collected regarding patient age, sex, education level, employment situation and whether they smoked. They were similarly asked if they slept alone or accompanied, and their height and weight were measured. They were asked whether they suffered any of the following conditions: diabetes mellitus, arterial hypertension, cancer, urinary incontinence, anxiety, or depression.
Data Analysis
To describe the sample, mean and standard deviation (SD) were used for the quantitative variables and frequency analysis for the qualitative variables. Differences in study variables depending on SQ (Good Sleeper/Poor Sleeper) were compared using the Chi square test or Fisher’s exact test for qualitative variables, and Student’s t-test for quantitative variables.
A multivariate binary logistic regression analysis was subsequently performed to examine the relationship between SQ and lifestyle habits. The Hosmer-Lemeshow test was used to determine goodness-of-fit (calibration) of the model, and ROC AUC was used to determine the discrimination capacity of the model
Results
A total of 261 patients were included in the study. 58.6% were female and mean age was 54.8 (SD: 15.7) years old. Mean BMI was 25.6 (SD: 4.1) and 54.0% were overweight or obese (BMI≥25). Almost half (48.7%) of the study population were found to have poor SQ. As shown in Table 2, the mean PSQI score for good sleepers was 3.5 (SD: 3.9), and for poor sleepers 9.7 (SD: 3.2) (p<0.001). Table 3 shows sample distribution as regards PSQI components. Statistically significant differences between good and poor sleepers were found in all of them. Table 4 shows patient behaviour as regards the lifestyle habits studied.
Total N=261 | Good Sleepers n=134 (51.3%) | Poor Sleepers n=127 (48.7%) | p-value | |
---|---|---|---|---|
PSQI; mean (SD) | 6.5 (3.9) | 3.5(1.2) | 9.7(3.2) | >0.001 |
Gender; n (%) Male Female | 108 (41.4) 153 (58.6) | 63 (58.3) 71 (46.4) | 45 (41.6) 82 (53.6) | 0.005 |
Age; mean (SD) | 54.8 (15.7) | 52.1 (15.3) | 57.5 (16.6) | 0.058 |
BMI; n (%) <24.9 25-29.9 ≥30 | 120 (46.0) 105 (40.2) 36 (13.8) | 63 (52.5) 57 (54.3) 14 (38.9) | 57 (47.5) 48 (45.7) 22 (61.1) | 0.264 |
Education level; n (%) No education Primary Secondary ‘A’ level / Vocational University | 15 (5.7) 53 (20.3) 39 (14.9) 44 (16.9) 110 (42.1) | 6 (40) 24 (45.3) 19 (48.3) 29 (65.9) 56 (50.9) | 9 (60) 29 (54.7) 20 (51.2) 15 (34.1) 54 (49.1) | 0.248 |
Sleeps; n (%) Alone Accompanied | 98 (37.5) 163 (62.5) | 40 (40.8) 94 (57.66) | 58 (59.2) 69 (42.3) | 0.008 |
Employment situation; n (%) Unemployed Working Student Retired | 22 (8.4) 152 (58.2) 9 (3.4) 78 (29.9) | 11 (50) 86 (53.6) 7 (77.8) 30 (38.5) | 11 (50) 66 (43.4) 2 (22.2) 48 (61.5) | 0.025 |
Smoker; n (%) No Yes | 258 (92.3) 20 (7.7) | 132 (51.2) 2 (66.7) | 126 (48.8) 1 (33.3) | 0.593 |
Diabetes mellitus; n (%) No Yes | 220 (84.3) 41 (15.7) | 118 (53.6) 16 (39) | 102 (46.4) 25 (61) | 0.086 |
Arterial hypertension; n (%) No Yes | 172 (65.9) 89 (34.1) | 89 (51.7) 45 (50.6) | 83 (48.3) 44 (49.4) | 0.856 |
Cancer; n (%) No Yes | 253 (65.9) 89 (34.1) | 132 (52.2) 2 (25) | 121 (47.8) 6 (75) | 0.130 |
Urinary incontinence; n (%) No Yes | 250 (95.8) 11 (4.2) | 133 (53.2) 1 (9.1) | 117 (46.8) 10 (90.9) | 0.004 |
Anxiety; n (%) No Yes | 224 (85.8) 37 (14.2) | 125 (55.8) 9 (24.3) | 99 (44.2) 28 (75.7) | <0.001 |
Depression; n (%) No Yes | 241 (92.3) 20 (7.7) | 129 (53.5) 5 (25) | 112 (46.5) 15 (75) | 0.014 |
PSQI: Pittsburgh Sleep Quality Index; SD: Standard Deviation; BMI: Body mass index.
PSQI Component | Total (n=261) | Good Sleepers n=134 (51.3%) | Poor Sleepers n=127 (48.7%) | p-value |
---|---|---|---|---|
Perceived Sleep Quality; n (%) Very good Fairly good Fairly bad Very bad | 46 (17.6) 150 (57.5) 58 (22.2) 7 (2.7) | 39 (84.8) 91 (60.7) 4 (6.9) - | 7 (15.2) 59 (39.3) 54 (42.5) 7 (5.5) | <0.001 |
Sleep Latency (minutes); n (%) < 15 16-30 31-60 >60 | 54 (20.7) 119 (45.6) 57 (21.8) 31 (11.9) | 38 (70.4) 83 (69.7) 12 (21.1) 1 (3.2) | 16 (29.6) 36 (30.3) 45 (78.9) 30 (96.8) | <0.001 |
Sleep Duration; n (%) >7 hours 6-7 hours 5-6 hours <5 hours | 143 (54.8) 75 (28.7) 27 (10.3) 16 (6.1) | 107 (74.8) 26 (34.7) 1 (3.7) 0 (0) | 36 (25.2) 49 (65.3) 26 (96.3) 16 (100) | <0.001 |
Sleep Efficiency; n (%) ≥85% 75-84% 65-74% <65% | 165 (63.2) 48 (18.4) 20 (7.7) 28 (10.7) | 120 (72.7) 14 (29.2) 0 (0) 0 (0) | 45 (27.3) 34 (70.8) 20 (100) 28 (100) | <0.001 |
Sleep Disturbances (PSQI score); n (%) 0 1-9 10-18 19-27 | 4 (1.5) 148 (56.7) 98 (37.5) 11 (4.2) | 4 (100) 105 (70.9) 25 (25.5) 0 (0) | 0 (0) 43 (29.1) 73 (74.5) 11 (100) | <0.001 |
Use of sleep medication; n (%) Not during the past month <1 time a week Once or twice a week ≥3 times a week | 191 (73.2) 13 (5.0) 10 (3.8) 47 (18.0) | 128 (67.0) 2 (15.4) 3 (30) 1 (2.1) | 63 (33.0) 11 (84.6) 7 (70.0) 46 (97.9) | <0.001 |
Daytime dysfunction; n (%) Not a problem at all A very minor problem Something of a problem A major problem | 128 (49.0) 90 (34.5) 36 (13.8) 7 (2.7) | 90 (70.3) 40 (44.4) 4 (11.1) 0 (0) | 38 (29.7) 50 (55.6) 32 (88.9) 7 (100) | <0.001 |
PSQI: Pittsburgh Sleep Quality Index.
How often… | ADEQUATE | INADEQUATE | |||
---|---|---|---|---|---|
N; n (%) | AN; n (%) | S; n (%) | AA; n (%) | A; n (%) | |
do you find your bed uncomfortable? | 134 (51.3) | 71 (27.2) | 50 (19.2) | 4 (1.5) | 2 (0.8) |
do you find your pillow uncomfortable? | 108 (41.4) | 70 (26.8) | 70 (26.8) | 10 (3.8) | 3 (1.1) |
do you find that the temperature in your bedroom is not appropriate? | 78 (29.9) | 72 (27.6) | 98 (37.5) | 12 (4.6) | 1 (0.4) |
do you sleep somewhere where there is too much light? | 164 (62.8) | 69 (26.4) | 23 (8.8) | 3 (1.1) | 2 (0.8) |
are you disturbed while sleeping? | 86 (33.0) | 55 (21.1) | 66 (25.3) | 29 (11.1) | 25 (9.6) |
do you look at the clock when unable to sleep? | 61 (23.4) | 59 (22.6) | 84 (32.2) | 26 (10.0) | 31 (11.9) |
do you go to bed worrying about something? | 35 (13.4) | 38 (14.6) | 117 (44.8) | 48 (18.4) | 23 (8.8) |
do you use your bed for activities other than sleeping or having sex? | 174 (66.7) | 30 (11.5) | 38 (14.6) | 10 (3.8) | 9 (3.4) |
do you drink coffee in the 4 hours before going to bed? | 188 (72.0) | 39 (14.9) | 28 (10.7) | 3 (1.1) | 3 (1.1) |
do you drink 2 or more glasses of wine/beer in the 4 hours before going to bed? | 167 (64.0) | 42 (16.1) | 44 (16.9) | 7 (2.7) | 1 (0.4) |
do you drink spirits or a shot in the 4 hours before going to bed? | 194 (74.3) | 48 (18.4) | 18 (6.9) | - | 1 (0.4) |
do you go to bed hungry? | 186 (71.3) | 55 (21.1) | 19 (7.3) | - | 1 (0.4) |
do you go to bed thirsty? | 186 (71.3) | 59 (22.6) | 13 (5.0) | 1 (0.4) | 2 (0.8) |
do you feel too full after supper before going to sleep (heavy evening meal)? | 132 (50.6) | 72 (27.6) | 51 (19.5) | 4 (1.5) | 2 (0.8) |
do you nap for longer than 1 hour? | 104 (39.8) | 66 (25.3) | 71 (27.2) | 11 (4.2) | 9 (3.4) |
do you get up at the same time every day? | 7 (2.7) | 9 (3.4) | 35 (13.4) | 159 (60.9) | 51 (19.5) |
do you go to bed at the same time every night? | 5 (1.9) | 17 (6.5) | 45 (17.5) | 175 (67.0) | 19 (7.3) |
do you stay in bed after waking up? | 60 (23.0) | 70 (26.8) | 75 (28.7) | 34 (13.0) | 22 (8.4) |
do you work in bed before going to sleep? | 221 (84.7) | 15 (5.7) | 20 (7.7) | 4 (1.5) | 1 (0.4) |
do you take exercise to the point of sweating in the 4 hours before going to bed? | 186 (71.3) | 33 (13.6) | 28 (10.7) | 10 (3.8) | 4 (1.5) |
do you do enervating activities before going to sleep? | 135 (51.7) | 69 (26.4) | 49 (18.8) | 8 (3.1) | - |
do you read things that you consider important in bed? | 138 (52.9) | 44 (16.9) | 60 (23.0) | 10 (3.8) | 9 (3.4) |
do you read things that you consider trivial in bed? | 138 (52.8) | 39 (14.9) | 64 (24.5) | 16 (6.1) | 4 (1.5) |
do you text on your mobile in bed? | 141 (54.0) | 31 (11.9) | 48 (18.4) | 23 (8.8) | 18 (6.9) |
do you watch TV in bed? | 176 (67.4) | 23 (8.8) | 32 (12.3) | 17 (6.5) | 13 (5.0) |
do you listen to the radio/podcasts/music in bed? | 142 (54.4) | 24 (9.2) | 54 (20.7) | 16 (6.1) | 25 (9.6) |
do you play video games in the hour before going to sleep? | 216 (82.8) | 14 (5.4) | 17 (6.5) | 10 (3.8) | 4 (1.5) |
do you have intense interaction on social media just before going to sleep? | 166 (63.6) | 31 (11.9) | 41 (15.7) | 14 (5.4) | 9 (3.4) |
do you use social media for trivial activities just before going to sleep? | 151 (57.9) | 31 (11.9) | 54 (20.7) | 21 (8.0) | 4 (1.5) |
N: Never; AN: Almost never; S: Sometimes; AA: Almost always; A: Always.
The multivariate analysis revealed a statistically significant relationship between being a “poor sleeper” and age (OR=1.032; CI95%:1.003-1.061), but the relationship between SQ and sex was not found to be significant. Patients who slept accompanied had a 52.1% lower risk of being a “poor sleeper” than patients who slept alone (OR=0.479; CI95%: 0.255-0.901). As regards comorbidities among patients, those with urinary incontinence were at 20 times higher risk of being a “poor sleeper” than patients not affected by this condition (OR=20.001; CI95%:2.055-194.771), and the risk for patients suffering anxiety was 3.950 times higher than for patients not affected by this condition (OR: 3.950; CI95%:1.585-9.840). Patients with diabetes mellitus had a 3.405 times higher risk than non-diabetic patients (OR: 3.405; CI95%: 1.347-8.607). Arterial hypertension and drinking coffee were not found to be risk factors (OR = 0.535; CI95%: 0.234-1.226 and OR = 0.406; CI95%: 0.149-1.107 respectively); they were however kept in the final multivariate analysis to serve as confounding variables. The other comorbidities among patients showed no statistically significant relationship with SQ. Physical exercise was a protective factor against poor SQ (OR = 0.221; CI95%: 0.081-0.603) and risk factors for poor SQ were being disturbed at night (OR = 3.606; CI95%: 1.892-6.872), going to bed preoccupied (OR = 3.145; CI95%: 1.528-6.471), reading trivial material (OR = 2.475; CI95%: 1.208-5.070), and playing video games (OR = 3.639; CI95%: 1.326-9.984). The Hosmer-Lemeshow value for this model was 4.682 (p=0.791) and AUC was 0.829 (CI95%: 0.780-0.879) (Table 5).
Raw OR | CI95% | Corrected OR | CI95% | |
---|---|---|---|---|
Gender Male Female | 1 1.617 | 0.983-2.659 | - | - |
Age | 1.023 | 1.006-1.040 | 1.032 | 1.003-1.061 |
BMI >25 >30 ≤30 | 1 0.931 1.737 | 0.551-1.574 0.821-3.713 | - | - |
Education level No education Prim/Sec ‘A’ / VT / University | 1 0.760 0.541 | 0.250-2.308 0.184-1.595 | - | - |
Sleeps Alone Accompanied | 1 0.506 | 0.304-0.842 | 1 0.479 | 0.255-0.901 |
Employment situation Unemployed Working Student Retired | 1 0.767 0.286 1.600 | 0.314-1.878 0.048-1.694 0.617-4.146 | - | - |
Smoker No Yes | 1 0.524 | 0.047-5.849 | - | - |
Diabetes mellitus No Yes | 1 1.808 | 0.915-3.572 | 1 3.405 | 1.347-8.607 |
AH No Yes | 1 1.048 | 0.628-1.749 | 1 0.535 | 0.234-1.226 |
Cancer No Yes | 1 3.273 | 0.648-16.524 | - | - |
Urinary incontinence No Yes | 1 0.088 | 0.011-0.698 | 1 20.004 | 2.055-194.771 |
Anxiety No Yes | 1 3.928 | 1.772-8.707 | 1 3.950 | 1.585-9.840 |
Depression No Yes | 1 3.455 | 1.217-9.808 | - | - |
Uncomfortable bed No Yes | 1 1.861 | 1.019-3.400 | - | - |
Uncomfortable pillow No Yes | 1 1.848 | 1.089-3.134 | - | - |
Correct temperature No Yes | 1 1.285 | 0.786-2.101 | - | - |
Light No Yes | 1 0.770 | 0.349-1.698 | - | - |
Disturbed No Yes | 1 3.048 | 1.838-5.055 | 1 3.606 | 1.892-6.872 |
Clock No Yes | 1 2.472 | 1.499-4.077 | - | - |
Preoccupied No Yes | 1 3.501 | 1.941-6.314 | 1 3.145 | 1.528-6.471 |
Sex No Yes | 1 1.469 | 0.813-2.652 | - | - |
Caffeine No Yes | 1 0.279 | 0.121-0.643 | 1 0.406 | 0.149-1.107 |
Wine No Yes | 1 0.726 | 0.393-1.341 | - | - |
Spirits No Yes | 1 0.593 | 0.226-1.558 | - | - |
Herbal medicines No Yes | 1 3.192 | 1.470-6.930 | - | - |
Hungry No Yes | 1.643 | 0.649-4.164 | - | - |
Thirsty No Yes | 1 2.447 | 0.825-7.251 | - | - |
Heavy evening meal No Yes | 1 1.341 | 0.744-2.418 | - | - |
Naps No Yes | 1 0.609 | 0.364-1.020 | - | - |
Time getting up No Yes | 1 1.626 | 0.573-4.613 | - | - |
Time going to bed No Yes | 1 1.409 | 0.580-3.420 | - | - |
Staying in bed No Yes | 1 1.564 | 0.959-2.549 | - | - |
Working in bed No Yes | 1 1.661 | 0.717-3.847 | - | - |
Physical exercise No Yes | 1 0.413 | 0.204-0.836 | 1 0.221 | 0.081-0.603 |
Enervating activities No Yes | 1 0.855 | 0.475-1.542 | - | - |
Trivial reading No Yes | 1 1.614 | 0.948-2.749 | - | - |
Important reading No Yes | 1 1.654 | 0.979-2.793 | 1 2.475 | 1.208-5.070 |
Use mobile No Yes | 1 1.202 | 0.720-2.006 | - | - |
TV No Yes | 1 0.986 | 0.557-1.744 | - | - |
Radio No Yes | 1 1.202 | 0.725-1.991 | - | - |
Video games No Yes | 1 1.537 | 0.720-3.283 | 1 3.639 | 1.326-9.984 |
Social networks interaction No Yes | 1 0.837 | 0.475-1.474 | - | - |
Social networks no interaction No Yes | 1 0.901 | 0.531-1.528 | - | - |
BMI: Body Mass Index; ‘A’: ‘A’ level, VT: Vocational Training. Hosmer-Lemeshow test: 4.682 (p=0.791); Cox & Snell R2= 0.311; Nagelkerke R2 = 0.415; AUC: 0.829 (CI95%: 0.780-0.879)
Discussion
One of the questions that this study aimed to clarify was whether community pharmacies may be an appropriate place to make assessments. The short period of time required to recruit the sample size, the large number of pharmacies and their distribution across the region, pharmacist training and patient trust in their pharmacist make community pharmacies an ideal place for conducting epidemiological studies, such as research into SQ, that require a large proportion of the population to be recruited without investing major effort.
This study revealed a high prevalence of patients with poor SQ (48.7%) among the population of Salamanca. Prevalence is higher than that found in other studies carried out in Spain using the same SQ measurement method (PSQI)16,20. However, these studies were conducted in other areas of the country, and it was not possible to establish the reasons for this difference in prevalence.
There are, unsurprisingly, considerable differences in the SQ dimensions measured using PSQI. Good sleepers perceived their sleep as “fairly good” or “very good”, whilst poor sleepers perceived it as “fairly poor” or “very poor”. Similarly, better values for sleep latency, sleep duration and sleep efficiency were obtained among good sleepers than among poor sleepers. Poor sleepers experienced more sleep disturbances, more daytime dysfunction and took more sleep medication. In this last respect, a comment must be made here: it is logical to think that patients who needed medication were those who had problems sleeping. However, after one month (the period over which SQ was measured using PSQI), patients taking such medication continued to report that they were suffering poor SQ. It may therefore be stated that the therapeutic strategy prescribed for treating sleep issues was ineffective, and that the pharmacist should have suggested that the patient saw their general practitioner for treatment review21.
Madrid-Valero et al. found significant differences in SQ in the Spanish population depending on age and gender16. These results match those found in this study as regards age, but not gender. Gender-related differences may have been eclipsed in the multivariate analysis by the effect of other study variables, because the bivariate analysis (Table 1) shows a clear difference in SQ according to gender.
Caffeine is widely consumed around the world. Yet despite this, evidence of the extent to which it affects sleep is not clear and depends on the amount of caffeine consumed and the tolerance and sensitivity of the person consuming it. Although high doses (several cups of coffee) shortly before going to bed may hinder sleep, there is no evidence in the non-clinical population that low or moderate consumption hinders sleep22. This may account for why, in this study, no statistically significant relationship is found between SQ and consuming caffeine a few hours prior to going to bed. In any case, this variable is shown to be a confounding variable in the presence of AH, and for this reason it was kept in the logistic model.
By contrast, the consumption of high doses of nicotine whether in the form of cigarettes, tablets or patches has been associated with sleep disorders23. However, the acute nervousness caused by stopping smoking has negative effects on sleep and, in the long term, there is no evidence that stopping smoking is beneficial for improving SQ22. Our study found no correlation between SQ and tobacco consumption. This could be explained by the low number of smokers in the study sample. Given that there are increasingly fewer smokers in Spain24, this may become a fairly insignificant risk factor in the near future.
The consumption of alcohol has also been shown to cause sleep disturbances, and recommendations range from avoiding high consumption of alcohol to not drinking at all before going to bed10. In addition, subsequent studies found that in people who are not alcohol-dependent, drinking alcohol (even a small amount) before going to bed may affect their sleep that night, although this will also depend on individual tolerance22. The majority of the study population either do not drink alcohol at all or only very occasionally, and therefore although they might experience poor sleep on a given night, this does not appear to be sufficient reason for them to describe their SQ as poor over the preceding month. This would account for the fact that the questions relating to alcohol consumption in this study show no relationship with SQ.
Another lifestyle habit highly recommended for improving SQ is physical exercise, although it should not be taken too near bedtime10. However, more recent pieces of research agree that physical exercise improves SQ20, even when taken shortly before going to bed22. It has also been shown to improve SQ in insomnia patients25. In our initial hypothesis, we posited that exercise was a predictive factor for SQ, and in this respect the results obtained matched the data expected.
Naps have been widely studied in scientific literature as having a possible effect on sleep, although there does not seem to be any clear link between daytime napping and broken nights22. The data obtained in this study support this observation. It must nevertheless be borne in mind that the question was framed in terms of naps lasting longer than one hour, so this result must be interpreted with caution.
Another of the most widely-made recommendations for achieving good SQ was to reduce stress levels before going to sleep, which is why individuals are encouraged not to do any activities that make them nervous or worried, but rather some kind of relaxing activity before going to bed10. Stress has indeed been found to cause problems getting to sleep and staying asleep26. This is why study participants were asked about activities such as reading things that they found important or not, watching TV, listening to the radio, etc. All such activities may favour or hinder proper sleep. Listening to relaxing music does not have the same effect as watching a football match. In any case, most of these activities were found not to have any relationship with SQ in this study, not even those relating to use of new technologies. This may be due to the highly general nature of the questions, which allowed subjects to use their own judgement when interpreting what they considered important or stressful. On the other hand, very few participants stated that they did these types of activities, which made it difficult to determine whether their effects on SQ were significant. Only playing video games and reading material that the participant considered trivial were found to be risk factors for poor SQ.
In addition to the foregoing, new technologies must be considered today. Their negative effect on SQ has not been clearly demonstrated27. It must be emphasised that the majority of research looking at the use of technology and its relationship with sleep only analyses how often it is used before going to sleep27, not why it is used28. This study investigated the frequency and intensity of technology use-related activities but even so, in our model only playing video games was found to have a significant bearing on SQ. Playing video games before going to sleep appear to cause a state of excitation not conducive to sleep; this might not be caused by other activities such as reading emails or news on social networks. However, the study by Carter et al29 showed that the use of technology among children and young people did have a considerable bearing. This fact was perhaps not observed in our study given the different age of the study population.
Several limitations must be considered for our study results to be correctly interpreted. Firstly, it must be borne in mind that given the type of study design used (cross-sectional), no causal relationship can be established between the variables analysed and poor SQ. However, the results do provide an overview of the current situation with regard to SQ in the population of Salamanca. It would be of interest to conduct prospective studies that enable causal relationships between lifestyle habits and poor SQ to be identified. Secondly, conducting this study in community pharmacies entails a potential selection bias, since people who visit such establishments usually have health issue; only in a few cases was this not so. Caution must therefore be exercised when extrapolating results.
In future research, it may be of interest to conduct longitudinal studies that enable causal relationships to be identified between specific lifestyle habits and poor SQ. Moreover, studying each lifestyle habit separately as regards time of day, frequency and intensity and comparing between groups may well clear up many of the existing doubts surrounding the lifestyle habits mentioned and poor SQ. This study shows that SQ can be assessed in community pharmacies. However, further research is needed to explore whether pharmaceutical interventions can improve SQ in the population.
Conclusion
Studying SQ was considered important because it is a factor that directly affects quality of life among the population. In the Spanish town of Salamanca, almost half of the study population stated that they suffered poor SQ. Although numerous lifestyle habits that may relate to poor SQ were studied, a statistically significant relationship was only found for a few of them. It was shown that physical exercise is a factor that protects against poor SQ, and being disturbed at night, going to bed preoccupied, reading trivial material and playing video games were risk factors for poor SQ. Other risk factors identified were Type II diabetes, anxiety and urinary incontinence. This notwithstanding, other studies with more tailored designs are required to demonstrate causality between the predictive variables analysed and SQ. In addition, community pharmacies appear to be a suitable place for conducting these types of study, given that they are found all over Spain and the people visiting them are willing to participate in activities suggested by their pharmacist.