Basic information of the participants
Table 1 shows the basic information collected from the 1,658 participants. The average age of the respondents was 70.41 years old (SD 7.63). The loneliness scores in the survey ranged between 21 and 80. A total of 31 (18.4%), 924 (55.7 %), and 429 (25.9%) of the respondents were assessed as having low, moderate, and high levels of loneliness, respectively, and the mean overall score for the participants was 43.17±9.46. Of all the participants, 50.7% were female, and 15.2% were over 80 years of age. Individuals who were part of a couple accounted for 69.8% of the respondents, and 31.1% of the participants reported less than 1000 yuan in economic income. A total of 62.1% reported that their income comes from their children, 69.1% had a primary school education or below, 63.0% worked in manual labour, 30.9% reported smoking, 46.1% reported consuming alcohol, 94.7% had good relationships with their family members, 30.2% reported being an empty nester, 17.3% reported having either 1 child or 0 children, and 32.8% reported having a chronic diseases.
Comparison of loneliness scores
There were significant differences in the loneliness scores among older adults with different characteristics, mainly including age (p<0.001), marital status (p=0.001), occupation (p<0.001), education (p<0.001), economic sources (p<0.001), economic income (p=0.002), smoking (p<0.001), drinking (p<0.001), relationships with family members (p=0.045), being an empty nester (p<0.001), the number of children (p<0.001) and having a NCD (p<0.001). The average score of an elderly individual with poor sleep quality was 45.04±8.86, which was significantly higher than that of an elderly individual with good sleep quality (41.66± 9.65) (t=7.742, p< 0.001).
Comparison of the PSQI scale and its component scores
The mean score for sleep quality was 6.673.42. Among the 1658 participants with a global score greater than 7, which accounted for 44.9% of the sample, the prevalence rate of poor sleep quality was 44.9% in rural elderly people in Shandong Province. As shown in Table 2, the average scores for sleep quality, subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction were 6.67±3.42, 1.14±0.76, 1.24±0.90, 0.61±0.84, 0.84±1.04, 1.34±0.67, 0.36±0.76 and 1.15±0.78, respectively. There was a statistically significant difference between the score of sleep quality and 5 PSQI scale dimensions (all except subjective sleep quality and habitual sleep efficiency) between the different levels of loneliness (p <0.05).
Contour analysis of average scores of PSQI for different levels of loneliness
A contour analysis of the average scores of the PSQI scale for different levels of loneliness in rural elderly people was conducted. The profile of the seniors who experienced loneliness in rural areas is not parallel to each other among the low group, the moderate group or the high group (F=12.000, p=0.000), and the contours of the high group were higher than those of the moderate and low group. For a horizontal profile analysis, the average scores of 7 factors, namely, subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication and daytime dysfunction, were different (F= 38.103, p=0.000), as shown in Figure 1.
Association between sleep quality and loneliness
The classification of loneliness in the rural elderly population was used as the dependent variable (Y=0, low level of loneliness, Y=1, moderate level of loneliness, Y=2, high level of loneliness), the sleep quality score was used as the independent variable, and age, marital status, occupation, economic income, relationships with family members, empty nester, number of children, smoking, drinking, BMI, chronic disease and quality of life were used as control variables. The relationship between the sleep quality and loneliness of elderly people was analysed by three ordinal regression models. Even after controlling for marital status, drinking, relationships with family members, occupation, economic income, chronic disease and quality of life, an increase in the odds of loneliness was associated with an increase in the sleep quality score (adjusted odds ratio [aOR] = 1.111, 95% confidence interval [95% CI] = 1.078-1.145). The worse the quality of sleep, the higher the degree of loneliness in the elderly sample. Scores in subjective sleep quality (aOR = 0.765, 95% CI = 0.649-0.902), sleep latency (aOR = 1.346, 95% CI = 1.178-1.537), sleep duration (aOR = 1.316, 95% CI = 1.139-1.522), use of sleeping medication (aOR = 1.175, 95% CI = 1.005-1.372), and daytime dysfunction (aOR = 1.267, 95% CI = 1.079-1.487) were significantly different between older adults with high levels of loneliness and those with moderate and low levels of loneliness. Older adults with higher PSQI scale scores in these 5 components had a higher risk of loneliness. Although older adults with higher scores in habitual sleep efficiency and sleep disturbances had a higher risk for loneliness, these differences were not statistically significant, as shown in Table 3.
Sensitivity analysis
A sensitivity analysis that excluded participants with either one child or no children (n = 287) yielded a similar result to that of Model 2 (OR 1.102; 95% CI 1.064–1.141; p = 0.000). The second sensitivity analysis that excluded participants whose BMI ≥ 24 and BMI<18.5 (n = 882) also yielded a result similar to that of Model 2 (OR 1.113; 95% CI 1.063–1.164; p = 0.000). The third sensitivity analysis that excluded participants with poor quality of life (n = 160) also yielded a result similar to that of Model 2 (OR 1.105; 95% CI 1.070–1.141; p = 0.000).