Muscular strength, mobility in daily life and mental wellbeing among older adult Inuit in Greenland. The Greenland population health survey 2018

ABSTRACT

The purpose was to analyse the association of muscular strength, muscle pain and reduced mobility in daily life with mental wellbeing among older Inuit men and women in Greenland. Data (N = 846) was collected as part of a countrywide cross-sectional health survey in 2018. Hand grip strength and 30-seconds chair stand test were measured according to established protocols. Mobility in daily life was assessed by five questions about the ability to perform specific activities of daily living. Mental wellbeing was assessed by questions about self-rated health, life satisfaction and Goldberg’s General Health Questionnaire. In binary multivariate logistic regression models adjusted for age and social position, muscular strength (OR 0.87–0.94) and muscle pain (OR 1.53–1.79) were associated with reduced mobility. In fully adjusted models, muscle pain (OR 0.68–0.83) and reduced mobility (OR 0.51–0.55) but were associated with mental wellbeing. Chair stand score was associated with life satisfaction (OR 1.05). With an increasingly sedentary lifestyle, increasing prevalence of obesity and increasing life expectancy the health consequences of musculoskeletal dysfunction are expected to grow. Prevention and clinical handling of poor mental health among older adults need to consider reduced muscle strength, muscle pain and reduced mobility as important determinants.

KEYWORDS:

• Inuit
• Greenland
• mobility in daily life
• muscular strength
• muscle pain
• mental wellbeing
• older adults

Introduction

Reduced capacity to carry out activities of daily living (ADL) is a consequence of old age. Loss of muscular strength, pain, obesity, sensory impairment and loss of balance are among the common causes of this reduction [1,2]. Muscular strength decreases with age and is associated with the performance of activities of daily living in a number of settings [3–7]. Reduced muscular strength and mobility have in several studies been shown to predict poor mental wellbeing among older adults [8,9]. Specifically, lower body impairment reduced life satisfaction, emotional and somatic wellbeing in later life [10] whereas another study found that although mobility and cognition decreased with age and depression increased, this did not affect happiness among older adults [11]. Older adults in Greenland cherish an active life but their physical abilities decrease with age, especially among women [12].

Hand grip test and chair stand test are two widely used tests to assess muscular strength. Handgrip strength is an indicator of upper body strength. It decreases with age and is lower for women than for men, in Greenland [13] and elsewhere [14,15]. Handgrip strength correlates with overall muscular strength [16,17] and is a predictor of overall mortality, cardiovascular death and disease, respiratory disease and cancer [18–21]. Chair stand test is a functional test which measures ability to rise from a chair. It is a test of lower extremity and central strength, especially muscular strength, balance and coordination but other functional domains are also involved, such as endurance [22]. It decreases with age and is lower for women than for men, in Greenland [13] and elsewhere [22,23] Several studies have concluded that it is a valid test for lower extremity strength [24–26]. Reference values for both tests have recently been published for the Inuit in Greenland [13].

A large number of instruments exist for the assessment of activities of daily living (ADL) among older adults. In the 2018 Greenland population health survey the number of questions about ADL were reduced to eight among which were five questions about physical mobility. All are part of a 26-item list of functional abilities proposed by Christensen and co-workers (2000). [27] The mobility questions have not been used in Greenland before. A comparison of the results from Greenland in 2018 with a study from Denmark in 2013 showed minimal differences regarding mobility [12,28].

The purpose of the study was to analyse the association of muscular strength with mobility in daily life, self-rated health and mental wellbeing and to compare men and women. We specifically hypothesised that low muscular strength was associated with reduced mobility and that low muscular strength and reduced mobility were associated with low self-rated health, low satisfaction with life and a high score on Goldberg’s General Health Questionnaire [29]. We furthermore explored the possibility of defining cut-point values for muscle strength in relation to mobility. This is the first study of predictors of mobility in daily life and of muscular strength and mobility as predictors of mental wellbeing among older adult Inuit in Greenland.

Methods

Data collection

Data was collected from 2017 to 2019 as part of a countrywide cross-sectional health survey in Greenland (Figure 1) [30]. The participants were selected through a stratified random sample of adults in Greenland, who had been born in Greenland or Denmark. From each of five strata defined according to geographical criteria (South, Mid, Northwest, North and East Greenland), 19 towns and villages were chosen at random. From 11 towns, a random sample of inhabitants aged 15+ years were invited, and from 8 villages all inhabitants were invited to participate in the study. Data was collected by interviews, self-administered questionnaires and clinical examinations. For the present study, participants aged 55+ were included. The participation rate in this age group was 59%. Interviews provided information about socio-demographic factors, health and activities of daily living. Questionnaires were developed in the Danish language, translated into Greenlandic (Kalaallisut), backtranslated and revised. Interviews were conducted in the participant’s language of choice, which was most often Greenlandic, by native Greenlandic speaking interviewers who had been trained in the study procedures. A total of 846 Inuit aged 55+ participated in the survey. Inuit ethnicity was defined by the interviewers at enrolment based on primary language and self-identification.

Figure 1. Greenland in the circumpolar region and 19 communities where data was collected in 2018. Names of villages in small font size.

Hand grip strength

A total of 846 participants aged 55 and above were invited to participate in the measurement of hand grip strength. Of these, 80 were excluded: 18 because of physical impairments, 8 because of equipment failure while 8 persons declined to participate. For 46 persons there was no information about why the test was not carried out. Three participants with incomplete measurements were also excluded bringing the total number of valid measurements among the 55+ year-old to 763. Those who participated were younger than those who did not (mean age 65 vs. 69 years; p < 0.001). The test was carried out by 11 examiners of whom 9 only spoke Danish. The examiners had no prior experience with the test but had been instructed in the measurement of hand grip strength as part of the general training in study procedures. Grip strength was measured by a SAEHAN DHD-1 digital hand dynamometer [https://www.procare.dk/da/produkter/haandtryks-kraftmaaling/digital-hand-dynamometer]. The participant was seated at a table with the feet firmly placed on the ground, the elbow resting on the table and the forearm parallel with the table. The dynamometer was adjusted to fit the participant’s hand. After instruction, the participant pressed the dynamometer until maximum strength was shown. The results were recorded in kilograms with one decimal. The test was performed 3 times with both hands alternating between hands. Hand dominance was noted. Some encouragement was allowed but not outright cheering. For statistical analysis the maximum of the measurements was chosen [31].

Chair stand test

846 participants aged 55 and above were invited to participate in the chair stand test (SC-30) as a measure of lower body strength. Of these, 102 were excluded: 54 because of pain in joints or back, 12 declined to participate, 10 were excluded because of heart disease or dizziness and 5 for other reasons, whereas the reason was not specified for 21 participants. Those who participated were younger than those who did not (65 vs. 70 years; p < 0.001). The total number of valid measurements was thus 744. The test was carried out by four examiners who all spoke Greenlandic. The examiners had no prior experience with the test but had been instructed in the chair stand test as part of the general training in study procedures. The participant was seated on a chair placed against the wall with the back touching the chair and the feet flat on the ground. The chair was not standardised but at each location a chair with a seat height of 43–45 centimetres without armrests was procured. The arms were crossed at the wrists and the palms were placed loosely around the collarbones. After instruction, a test attempt was carried out. Participants who did not pass the test attempt scored 0. The participants were then asked to stand and sit down on the chair as many times as possible within 30 seconds without using the arms. Some encouragement was allowed but not outright cheering. The number of times the participant was able to fully stand up was recorded. The exercise was stopped if the participant became tired and short of breath, began to use the arms or if the examiner was otherwise concerned about the safety of the participant [22].

Sociodemographic data

Age was calculated as date of examination minus date of birth truncated. Sex and date of birth were derived from the civil registration number. Education was recorded from survey information on school and occupational education categorised into four groups according to the highest educational achievement: primary and secondary school only; short vocational education (1–2 years); medium long education (2–3 years); long education, university (4+ years). Information on education was available for 843 participants (99.6%). Participants were asked about their ownership of six household items: video/DVD player, computer, microwave oven, washing machine, dishwashing machine and internet. Here, 0/1 answers were added, yielding a household asset score ranging from 0 to 6. The household asset score is an indicator of social position that is closely associated with more traditional measures of socioeconomic position, such as education and income, but it has certain practical advantages and is often used in a Greenlandic context [32,33]. All participants answered these questions.

Mobility in daily life

Five questions were asked about mobility including ability to do light household chores, walk around indoors, walk 400 m without resting, climb or descend a flight of stairs without resting and carry 5 kgs (e.g. a shopping bag). The reply categories were “1. Without difficulty”, “2. With some difficulty”, “3. With much difficulty” and “4. Not at all”. Participants who reported “Without difficulty” to all questions were categorised as having unimpaired mobility. Information was available for 834 participants (99%).

Health and wellbeing

Muscle pain was assessed by two questions about pain and discomfort in the back and extremities, respectively. The questions ran “Have you within the last two weeks been bothered by pain or discomfort?” Reply categories were “1. No”, “2. Yes, a little”, and “3. Yes, a lot”. Replies were added to give a pain score that ranged from 2 to 6. Information was available for 841 participants (99%).

Three aspects of wellbeing were studied: self-rated health, satisfaction with life and mental vulnerability. Self-rated health was assessed by the question “How would you rate your health in general?” Answers included “1. Really good”, “2. Good”, “3. Average”, “4. Poor” and “5. Very poor”. The answers were dichotomised with the two first categories being good self-rated health (57%) and the three last poor self-rated health. Information was available for 842 participants (99.5%). Satisfaction with life in general was assessed with the question “How satisfied are you with your life in general?”. Answers included “1. Very satisfied”, “2. Somewhat satisfied”, “3. Neither satisfied nor dissatisfied”, “4. Somewhat dissatisfied”, and “5. Very dissatisfied”. The answers were dichotomised into “Very satisfied” (74%) vs. other answers. Information was available for 837 participants (99%). Mental vulnerability was estimated by the 12-question version of the General Health Questionnaire [29]. The score was dichotomised into robust (72%) and vulnerable with the cut-point at 2+ [34]. Information was available for 560 participants (66%).

Statistics

Statistical analyses included means with ANOVA test, cross tables with chi-square tests and binary multivariate logistic regression analyses by the standard statistical software IBM SPSS Statistics version 28.0 or higher. The distribution of muscular strength measurements was assessed as normally distributed by visual inspection of Q-Q plots. Analyses were performed separately for men and women and for men and women combined with mental health as outcome and age and social position as confounders [30,35,36]. For model control we used the Hosmer-Lemeshow goodness-of-fit tests which showed good model fit in 70 of 72 models (97.2%).

Results

In Table 1 basic demographic and social characteristics of the population of 846 Greenlandic Inuit aged 55+ years are shown. Table 2 shows the means and prevalence among men and women and in 5-year age groups of muscular strength, muscle pain, reduced mobility in daily life and three outcome variables for wellbeing. More than 98% had answered the interview about mobility in daily life, self-rated health and life-satisfaction whereas only 66% had answered the General Health Questionnaire which was placed in a separate self-administered questionnaire. Muscular strength was higher among men than among women and decreased significantly by age, whereas muscle pain showed no variation with age or sex. Reduced mobility was higher among women than among men and increased significantly with age. Self-rated health and life-satisfaction were similar among men and women whereas mental vulnerability was more prevalent among women. There was no statistically significant variation by age but among men self-rated health was highest in the oldest age groups.

Table 1. Population characteristics of 846 Greenlandic Inuit aged 55 + . Greenland Population Health Survey 2018.

	N	Mean (sd)	Range
Age (years)	846	65.5 (7.6)	55–94
Sex	N	%
Men	388	45.9
Women	458	54.1
Socioeconomic indices
Education
Primary/secondary school	423	50.2
Short further education (< 2 years)	275	32.6
Medium long further education (2–3 years)	132	15.7
Long further education (4+ years)	13	1.5
Missing	3	-
Household asset score
0–2	263	31.1
3	145	17.1
4	147	17.4
5	170	20.1
6	121	14.3

Table 2. Prevalence of muscular strength and pain, mobility in daily life, and wellbeing among Inuit in Greenland. N = 846.

		Muscular strength, pain			Mobility	Wellbeing
		Hand grip strength (kg)	Chair stand score	Muscle pain	Reduced mobility	Good self-rated health*	Satisfied with life**	Mentally robust (GHQ)***
		n = 763	n = 744	n = 841	n = 834	n = 842	n = 837	n = 560
	N	kg	score	score	%	%	%	%
Men	388	39.0	13.9	3.2	29.2	59.2	71.9	78.4
Women	458	22.3	11.5	3.3	47.9	55.4	76.1	66.2
	p	<0.001	<0.001	0.10	<0.001	0.30	0.18	<0.001
Age group
Men
55–59 years	104	45.1	15.9	3.3	17.5	58.7	62.1	77.9
60–64 years	88	43.1	14.5	3.0	20.7	64.8	72.7	81.2
65–69 years	85	36.5	13.2	3.2	28.2	56.5	78.8	80.7
70–74 years	63	33.6	12.2	3.1	38.7	46.0	72.6	79.4
75–79 years	33	27.8	11.0	3.1	56.3	71.9	78.1	61.5
80–84 years	12	27.6	10.2	3.3	63.6	75.0	75.0	-
85+ years	3	-	-	-	-	-	-	-
	p	<0.001	<0.001	0.69	<0.001	0.10	0.16	0.59
Women
55–59 years	118	26.0	12.9	3.2	37.6	51.7	70.1	68.4
60–64 years	118	23.7	12.6	3.3	38.8	61.5	81.2	68.5
65–69 years	94	21.6	11.4	3.3	42.4	54.8	80.4	61.3
70–74 years	64	18.8	9.6	3.4	62.5	53.1	75.0	67.7
75–79 years	35	17.6	8.8	3.6	66.7	41.2	72.7	60.0
80–84 years	18	15.2	8.5	3.4	88.9	50.0	66.7	-
85+ years	11	13.9	3.4	3.0	90.9	100.0	81.8	-
	p	<0.001	<0.001	0.71	<0.001	0.18	0.37	0.85

* dichotomised into Really good, Very good vs. Average, Poor, Very poor

** dichotomised into Very satisfied vs. four categories of less satisfaction

***dichotomised into Robust (GHQ-12 score 0–1.5) vs. Vulnerable (GHQ-12 score 2+)

Table 3 presents logistic regression models with reduced mobility as outcome variable and muscular strength, age, social position and muscle pain as independent variables. Low hand grip strength and chair stand score as well as muscle pain were associated with reduced mobility. There was no sex difference in the model with hand grip strength, but female sex was significantly associated with reduced mobility in the model with chair stand score as measure of muscular strength. Otherwise, the most striking difference between men and women was the association of low social position with reduced mobility among women.

Table 3. Predictors for mobility in daily life among Greenlanders aged 55 + . Odds ratios for reduced mobility. Binary logistic regression models with all variables entered.

	Men		Women		All
Model 1 with hand grip strength (N = 755)	OR*	p	OR*	p	OR*	p
Gripstrength (kg)	0.94	0.002	0.93	0.003	0.94	<0.001
Age (year)	1.04	0.06	1.02	0.28	1.03	0.020
Sex	-	-	-	-	0.94	0.823
Social position (score)	0.96	0.62	0.79	0.001	0.86	0.006
Muscle pain (score)	1.77	<0.001	1.79	<0.001	1.78	<0.001
Model 2 with chair stand test score (N = 740)
Chair stand score (count)	0.88	<0.001	0.87	0.003	0.87	<0.001
Age (year)	1.06	0.005	1.03	0.28	1.05	0.001
Sex	-	-	-	-	1.92	<0.001
Social position (score)	0.90	0.62	0.83	0.001	0.86	0.010
Muscle pain (score)	1.53	<0.001	1.73	<0.001	1.64	<0.001

* Odds ratio for reduced mobility

The association between muscular strength and mobility in daily life was linear and natural cut-off points for low muscular strength were not obvious. From linear regression analyses we calculated the hand grip strength that corresponded to 50% of the population having reduced mobility in daily life score at 20.8 kg (0.50 = 0.798–0.0143*20.8). This corresponds to the 25% percentile of hand grip strength. The chair stand score that corresponded to 50% of the population having reduced mobility in daily life score was 8.1 (0.50 = 0.775–0.0337*8.1). This corresponds to the 15% percentile of the chair stand score.

Social position and age were directly associated with good self-rated health and life satisfaction, while male sex and social position were directly associated with mental robustness (Table 4).

Table 4. Association of muscular strength, muscle pain and mobility in daily life with three measures of mental wellness among Greenland Inuit aged 55 + . Binary logistic regression models with age and social position as confounders.

	Good self-rated health (N = 740–842)		Satisfied with life (N = 740–837)		Mentally robust (N = 517–560)
Men	OR*	p	OR*	p	OR*	p
Age (years)	1.02	0.17	1.04	0.011	0.99	0.62
Social position (score)	1.34	<0.001	1.13	0.09	1.18	0.08
Models with one predictor adjusted for age and social position
Model 1. Grip strength (kg)	1.02	0.33	1.03	0.05	1.01	0.52
Model 2. Chair stand score	1.07	0.004	1.10	<0.001	1.08	0.03
Model 3. Muscle pain (score)	0.71	<0.001	0.74	0.002	0.76	0.04
Model 4. Reduced mobility	0.50	0.005	0.38	<0.001	0.35	0.002
Model 5. Full model with grip strength, adjusted for age and social position
Grip strength (kg)	1.01	0.59	1.02	0.19	1.00	0.95
Muscle pain (score)	0.73	0.003	0.79	0.03	0.84	0.23
Reduced mobility	0.58	0.05	0.46	0.008	0.32	0.003
Model 6. Full model with chair stand score, adjusted for age and social position
Chair stand score	1.04	0.06	1.07	0.01	1.05	0.16
Muscle pain (score)	0.74	0.004	0.79	0.04	0.84	0.26
Reduced mobility	0.62	0.09	0.52	0.03	0.39	0.01
Women
Age (years)	1.03	0.04	1.05	0.01	1.01	0.78
Social position (score)	1.29	<0.001	1.55	<0.001	1.36	0.000
Models with one predictor adjusted for age and social position
Model 1. Grip strength (kg)	1.03	0.19	1.01	0.64	1.06	0.03
Model 2. Chair stand score	1.08	0.002	1.09	0.005	1.06	0.09
Model 3. Muscle pain (score)	0.53	<0.001	0.68	<0.001	0.79	0.04
Model 4. Reduced mobility	0.33	<0.001	0.44	0.001	0.61	0.06
Model 5. Full model with grip strength, adjusted for age and social position
Grip strength (kg)	1.01	0.75	0.99	0.83	1.05	0.05
Muscle pain (score)	0.62	<0.001	0.74	0.004	0.80	0.08
Reduced mobility	0.47	0.001	0.51	0.02	0.67	0.17
Model 6. Full model with chair stand score, adjusted for age and social position
Chair stand score	1.02	0.46	1.05	0.15	1.03	0.33
Muscle pain (score)	0.58	<0.001	0.81	0.07	0.83	0.15
Reduced mobility	0.52	0.008	0.60	0.08	0.79	0.43
All
Age (years)	1.03	0.010	1.04	0.001	1.00	0.819
Sex	0.89	0.419	1.30	0.103	0.52	0.001
Social position (score)	1.31	<0.001	1.32	<0.001	1.28	<0.001
Models with one predictor adjusted for age, sex and social position
Model 1. Grip strength (kg)	1.02	0.113	1.02	0.227	1.03	0.050
Model 2. Chair stand score	1.07	<0.001	1.09	<0.001	1.07	0.006
Model 3. Muscle pain (score)	0.61	<0.001	0.71	<0.001	0.78	0.003
Model 5. Full model with grip strength, adjusted for age and social position
Model 4. Reduced mobility	0.40	<0.001	0.41	<0.001	0.49	0.001
Grip strength (kg)	1.01	0.505	1.00	0.795	1.02	0.199
Model 6. Full model with chair stand score, adjusted for age and social position
Muscle pain (score)	0.67	<0.001	0.76	<0.001	0.82	0.042
Reduced mobility	0.51	<0.001	0.47	<0.001	0.51	0.003
Chair stand score	1.03	0.055	1.06	0.004	1.04	0.085
Muscle pain (score)	0.65	<0.001	0.80	0.006	0.85	0.090
Reduced mobility	0.56	0.002	0.56	0.005	0.60	0.032

* Odds ratio for good mental health

In logistic regression models adjusted for age, sex and social position, chair stand score, but not grip strength, absence of muscle pain and unrestricted mobility in daily life were directly associated with mental wellbeing. In full models separately for hand grip strength and chair stand score and adjusted for age, sex and social position, muscle pain and reduced mobility were associated with mental wellbeing. Hand grip strength was not associated with mental wellbeing, whereas chair stand score was associated with life satisfaction. The most important difference between men and women was the higher odds ratio for social position as a covariate for life satisfaction and mental robustness among women than among men.

Finally, Table 5 shows models with all explanatory variables and confounders entered simultaneously. There were some differences between the determinants for the three measures of mental health but, except for sex, the determinants for good self-rated health and satisfaction with life were similar: age, social position and chair stand score were directly associated with good mental health, while muscle pain and reduced mobility were negatively associated and grip strength was not associated. Being mentally robust was directly associated with social position and negatively with reduced mobility. Female sex was directly associated with life satisfaction only.

Table 5. Association of age, sex, social position, muscular strength, muscle pain and mobility in daily life with three measures of mental wellness among Greenland Inuit aged 55 + . Binary logistic regression with all variables entered in the models.

	Good self-rated health (N = 740–842)		Satisfied with life (N = 740–837)		Mentally robust (N = 517–560)
	OR*	p	OR*	p	OR*	p
Age (years)	1.05	0.002	1.07	0.000	1.02	0.273
Sex	1.30	0.333	2.31	0.006	0.72	0.370
Social position (score)	1.25	0.000	1.21	0.002	1.20	0.010
Grip strength (kg)	1.01	0.697	1.00	0.822	1.02	0.256
Chair stand score	1.04	0.046	1.05	0.014	1.03	0.271
Muscle pain (score)	0.68	0.000	0.80	0.007	0.83	0.073
Reduced mobility	0.54	0.001	0.51	0.002	0.55	0.014

* Odds ratio for good mental health

Discussion

Decreased hand grip strength and chair stand score were both associated with reduced mobility in daily living. This was in accordance with our first hypothesis. The associations were similar for men and women, and for both men and women muscle pain was another important predictor of reduced mobility. Additionally, among women low social position was associated with reduced mobility, whereas among men age was associated with reduced mobility. A number of studies from different countries have shown similar associations of activities of daily living with hand grip strength [3,5,6] chair stand score [5], sarcopenia [4] and slow gait speed [7]. Our finding of an association between low social position and reduced mobility confirmed the observations of other studies [37,38].

In logistic regression models with age, sex and social position as confounders, chair stand score, muscle pain and reduced mobility, but not hand grip strength, were associated with mental wellbeing. This was in accordance with our second hypothesis. In full models adjusted for age, sex and social position and with muscular strength, pain and reduced mobility entered simultaneously, muscular strength was not significant but pain and reduced mobility were. Analyses for men and women separately reduced the number of participants in the models and thus the statistical strength. In particular, analyses with mental robustness as outcome failed to reach statistical significance. Models with all variables entered revealed that age, social position, absence of muscle pain and normal mobility were directly associated with good self-rated health. Age, female sex, social position, chair stand score, absence of muscular pain and normal mobility were directly associated with life satisfaction, whereas only social position and normal mobility were associated with mental robustness. Studies from the US and Sweden showed similar associations of impaired functional ability and reduced mobility with both physical and mental health related quality of life [10,39]. Our study thus supports international knowledge about the importance of mobility in daily life for mental wellbeing among older adults, but also points to other important determinants.

Our data did not permit us to define a natural cut-point for muscular strength below which activities of daily living are performed drastically less well than by stronger participants. In the literature, values of 26–28 kg for men and 16 kg for women have been proposed for grip strength [18,40]. These values are not contradicted by our results, but it is not intuitively obvious that the cut-point should be different for men and women. For the chair stand test, a score of 8 for both men and women has been described [41], which is in accordance with our results.

The non-participation rate was high for hand grip strength, chair stand test and mental robustness and non-participation increased with age. The reasons for non-participation in the tests of muscle strength were most often related to disability and/or pain and this differential non-participation likely would bias the association between strength and the other outcomes towards the null hypothesis. However, a sensitivity analysis with the muscular strength of non-participants set at zero did not alter the results to any considerable extent. The reason for non-participation in the questions about mental robustness was that many participants failed to complete the self-administered questionnaire due to lack of time, functional illiteracy, reduced sight and other reasons not related to muscle strength (own observations, unpublished). The fewer participants in the analyses of mental robustness of course reduced the statistical strength of these models but probably did not introduce bias.

Muscular strength has not been measured in Greenland at the population level before the present survey. We used standard methods and have published reference values [13]. The assessment of muscle pain was based on two questions about pain in the back and extremities. These are part of a longer list of pain and physical as well as mental discomfort that has been used in the population health surveys in Greenland and Denmark since 1987.

In a systematic review, 51 questionnaires for activities of daily living were identified and evaluated for their psychometric properties [42]. Two of these were specifically recommended for future research and care practice in older community dwelling populations, namely the Functional Autonomy Measurement System (SMAF) [43] and the Functional Independence and Difficulty Scale (FIDS) [44]. These instruments are extensive and have 29 and 14 items, respectively. They are therefore not suited for general population health surveys where numerous topics compete for space in the questionnaire. From a list of 26 questions about activities of daily living [27] we used a reduced set of eight questions among which were five questions about physical mobility. Three of these questions have been used in the Danish population health surveys since 2005 but we chose to keep an additional two questions about light impairment in order to be able to differentiate better between reduced and normal mobility.

Self-rated health is a standard question used worldwide in epidemiological and clinical studies. It is determined by physical and mental health as well as material, psychosocial and behavioural factors [45]. In Greenland, the original categories of answers are still used (Really good /Good/Fair /Poor /Very poor) instead of the newer categories (Excellent /Very good /Good /Less than good /Poor) but in a cross-sectional analysis as the present this is believed to be unimportant. In conjunction with the development of a new set of questions to older adults, the question about satisfaction with life in general was added to the survey in Greenland in 2018 on inspiration by the similar survey among Inuit in Nunavik, Canada [46]. It is related to self-rated health and General Health Questionnaire (Kappa 0.24 and 0.27, respectively) but has not been validated separately and was included on its face value. The General Health Questionnaire was developed as a measure of mental illness in the general population [47,48]. It has been validated against SCAN Present State Examination in Greenland [34,49].

Strengths and weaknesses

It is a strength of the study that data was collected in a countrywide population health survey and as such is representative of Greenlandic Inuit from towns and villages. It is the first study of muscular strength, mobility in daily life and mental wellbeing among older adult Inuit and as such broadens the international and intercultural validity of our knowledge. It is a further strength that data was collected from questionnaires developed in Kalaallissut which is the vernacular of most Inuit in Greenland, and administered by native Kalaallissut-speaking interviewers. It is a weakness that since older people make up a rather small proportion of the population in Greenland and the participants were randomly selected, the number of participants was small in the oldest age groups: only 48 men and 64 women were aged 75+ and among these the non-participation rates for grip strength and chair stand test were high. Also, given the short life expectancy in Greenland (69 and 74 years, respectively, for men and women) there may be a healthy survivor bias. Finally, since the study is cross-sectional causal inferences cannot be conclusively established.

Conclusion

Muscular strength was directly associated with mobility in daily life which among women was directly associated with self-rated health and among men with life-satisfaction and mental robustness. Age, social position and muscle pain were important contributing determinants. In a society with an increasingly sedentary lifestyle, increasing prevalence of obesity and increasing life expectancy, the health consequences of musculoskeletal dysfunction are expected to grow.

Prevention and clinical handling of poor mental health among older adults need to consider reduced muscle strength, muscle pain and reduced mobility as important determinants. Improvement of muscular strength through strength training as well as disability aids, disability friendly interior design, and treatment of muscle pain are relevant tools for improving mental wellbeing among older adult Greenlanders.

Ethics

Ethical approval of the study was obtained from Greenlandic Ethics Committee (KVUG 2017-05) and written informed consent was obtained from all participants.

Acknowledgments

We thank the interviewers, examiners, local citizens who helped make the survey feasible, and the participants who willingly gave their time.

Disclosure statement

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

Additional information

Funding

The study was funded by the Department of Health and the Department of Social and Legal Affairs of the Greenland government. Veluxfonden; Velux Fonden.