Table 2.

Study characteristics.

(First Author) (Year) (Country)	Main Objective	Design	Setting	Type of Diabetes	Sample Demographics	Main Results
Blazer, D.G. (1986–1997) (US) [12]	Assessment of association between depression, obesity and diabetes.	Observational, cross-sectional and longitudinal survey	House hold survey	Not specified	N = 4162 Age ≥ 65 years	In the controlled and uncontrolled analyses, functional impairment (p < 0.001), female gender (p < 0.05), cognitive impairment (p < 0.01), and lower education were found to be associated with depression, diabetes, and high BMI (p < 0.05). The frequency of comorbidity between depression and diabetes was 2.6%.
Black, S.A. (1995–2001) (US) [6]	Assessment of impact of diabetes and depression on poor health outcomes in diabetes patients.	Longitudinal survey	In-home face-to-face interviews	T2DM	N = 2830 Age ≥65 years	Significant relationship was seen between depression and diabetes. About 24% of the patients had minor depression, 9% of the patients had major depression, and 47% of the patients had diabetes with minimum levels of depression.
Chiechanowski, P.S. (1999) (US) [8]	Assessment of association between diabetes, depression, PF, self-care, and HbA1c levels. Moreover, assessment of intensity of depression and HbA1c levels in patients with T1DM as compared the patients with T2DM.	Cross-sectional observational study	Tertiary care specialty clinic	T1DM, T2DM	N = 276 T1DM patients N = 199 T2DM patients Mean age of the relevant group = 48.8 ± 15.9 years	A significant association was seen between depression, glycemic control (p < 0.0001), HbA1c levels (p < 0.0001), PF (p < 0.01), and adherence to self-care behavior (p < 0.0001). Similarly, a significantly greater number (66.7%) of T1DM patients with HbA1c levels >8 were found to be depressed than T2DM depressed patients (37.5%) (p = 0.02).
Zuberi, S.I. (2008–2009) (Pakistan) [46]	Assessment of association between depression, self-care, and diabetes.	Cross-sectional study	Tertiary care hospital	T2DM	N = 286 diabetes patients Age = 31–60 years	Depression in male diabetes patients was lesser than female diabetes patients by the values; 39.2 and 60.8 respectively (p = 0.03). Moreover, HbA1c levels were significantly higher in depressed patients than in non-depressed diabetes patients (8.5% vs. 7.7%, p < 0.001).
Munshi, M. (2005) (US) [13]	Assessment of the association between cognitive dysfunction and glycemic control.	Cross-sectional study	Geriatric diabetic clinic	Not specified	N = 60 Age ≥ 70 years	Results showed that 34% of diabetes patients had low scores of CIB, whereas 38% of the patients had low CDT scores. Both the tests CIB (r = −0.37, p < 0.004) and CDT (r = −0.38, p < 0.004) had an inverse correlation with HbA1c levels. Furthermore, 33% of the patients were depressed, and 33% of the patients had history of falls, whereas 39% of the patients had poor IADL scores.
Yaffe, K.Y. (1998–1999) (US) [14]	To investigate the association between metabolic syndrome and cognitive function, and effect of inflammation on this association.	Longitudinal cohort study	Sacramento area and the surrounding California counties	Hyperglycemia associated with metabolic syndrome	N = 1624 Age ≥ 60 years	Rate of cognitive decline was found to be greater in patients with metabolic syndrome having hyperglycemia. Low scores of DelRec (p = 0.02) proved the finding. Similarly, low 3MS scores (p = 0.03) in the patients with inflammation, showed the impact of inflammation on cognitive decline.
Yaffe, K. (1997–2006) (US) [16]	Association between diabetes and cognitive decline and impact of glycemic control on cognitive function.	Prospective cohort study	Community clinics	Not specified	N = 3069 Age = 70–79 years	Participants with DM showed decline in cognitive function, and had low scores of cognitive status, i.e., 3MS (p = 0.001) and DSS (p = 0.001). Likewise, a significant association was also observed between HbA1c levels and cognitive decline, which was shown by low 3MS (p = 0.003) and DSS (p = 0.04) scores in the diabetes patients.
Yaffe, K. (1997–2008) (US) [15]	Assessment of association between hypoglycemia and dementia.	Prospective study	General population	Not specified	N = 783 Age = 70–79 years	Results indicated that 7.8% of diabetes patients had incidence of hypoglycemia, whereas 18.9% of the patients suffered from dementia. The incidence of dementia was double in patients facing hypoglycemia (p < 0.001). In the same way, the patients having dementia were at a higher risk of developing hypoglycemia (p < 0.001).
Turnbull, P.J. (2002) (UK) [29]	Assessment of nutritional status in diabetes patients and its impact on PF.	Case control study	General community	Not specified	N = 35 diabetes patients N = 35 non-diabetes patients Age > 65 years	Diabetes patients scored significantly lower on MNA (p < 0.01). These scores had significant correlation with BI (p < 0.01).
Vischer, U.M. (2010) (Switzerland) [41]	Assessment of prevalence of malnutrition elderly.	Prospective study	The Geneva Geriatric Hospital	Not specified	N = 146 Age > 65 years	Low scores of MNA indicated high prevalence of malnutrition in 77.1% of the diabetes patients. Moreover, in these patients, MNA scores were significantly associated with HbA1c levels (p = 0.0014).
Hubbard, R.E. (Canada) (2010) [35]	Comparison of prognostic value of frailty and number and severity of co-morbidities in older diabetes patients.	Longitudinal prospective cohort study	General community in five Canadian regions	Not specified	N = 2305 Age ≥ 70 years	There was a strong relationship between diabetes and medium-term mortality HR = 1.42 (CI 95% = 1.2–1.69). Frail diabetes patients had 2.62 times (CI 95% = 1.36–5.06) greater tendency of having diabetes complications than non-diabetes patients of same age. Moreover, the diabetes patients had more co-morbidities than non-diabetes patients (p < 0.005).
Maurer, M.S. (2005) (US) [17]	To investigate the association between diabetes and the risk of falls in the elderly.	Prospective cohort study	A long-term care facility	Not specified	N = 139 Age ≥ 60 years	The incidence rate for falls in diabetic patients as compared to non-diabetic patients was 70% and 30% respectively (p < 0.001).
Nelson, J.M. (2007) (US) [18]	Assessment of association between glycemic control and risk of falls in frail and non-frail elderly diabetes patients.	Retrospective, case-control study	A health maintenance organization	Not specified	N = 111 Age ≥ 75 years	Risk of falls increased in the patients with HbA1c levels ≤7 (p = 0.01).
Kalyani, R.R. (2010) (US) [19]	Assessment of the association between diabetes and functional disability in older adults, and the impact of HbA1c levels and other comorbidities on this association.	Cross-sectional, retrospective study	General community non, institutionalized population	Not specified	N = 6097 civilians Age ≥ 60 years	The prevalence of disability in GPA of the patients was found to be 73.6%, in LEM 52.2% and in IADL 43.6%. In addition, diabetes was associated with increased chances of disability by 2–3 times (p < 0.05). CVD and poor glycemic control had up to 85% more chance of diabetes-associated disabilities.
Kuo, H.K. (2005) (US) [20]	Assessment of the impact of BP and DM on physical and cognitive function.	Longitudinal prospective study	Independent living older subjects in six field sites in the US	Not specified	N = 2802 Age = 65–94 years	In terms of PF, patients with stage 1 (p = 0.03) and stage 2 (p = 0.007) hypertension showed a faster reduction in PF; similarly, those with DM also showed a decline in PF (p = 0.005), specifically in IADL. With respect to cognitive function, BP showed negative impact on memory (p = 0.008), stage 1 (p = 0.03), and stage 2 (p = 0.005) hypertension resulted in a reduction in reasoning; however, DM was a cause of a reduction in cognitive function DSS (p = 0.02).
Sinclair, A.J. (2008) (UK) [30]	Assessment of the nature of functional deterioration in older diabetes patients.	Case control study	General community	Not specified	N = 403 cases N = 403 controls Age ≥ 65 years	Diabetes patients had a greater number of comorbidities than non-diabetic patients (p < 0.0001) and they had a greater risk of severe functional deterioration (p < 0.001).
Lin, E.H. (2004) (US) [21]	Assessment of association between self-care of diabetes medication adherence, preventative services, and depression.	Cross-sectional and longitudinal retrospective survey	Primary care clinics	T2DM	N = 4500 Mean age of the relevant group = 63 ± 13.4 years.	Results show that 19.5% (p < 0.005) of the patients were non-adherent to the therapy, while 12% of the patients had major depression, which had an association with lower PF (p < 0.0001). Moreover, the depressed patients also had poor self-care activities (p < 0.0001).
Chou, K.L. & Chi, I. (1996) (China) [7]	Assessment of association between diabetes and disability, and the impact of diabetes complications on this association.	Cross-sectional study	Non-institutionalized population (general community)	Not specified	N = 2003 Age ≥ 60 years	Diabetic patients had a greater risk of poor performance of ADLs and IADLs than non-diabetic patients, and their inability to perform self-care was 3.5 times greater than non-diabetic patients (p < 0.01).
Dhamoon, M.S. (1993–2001) (US) [22]	To evaluate that diabetes acts as a long-term predictor of disability.	Prospective cohort study	General community	Not specified	N = 3298 Mean age of the relevant group = 69.2 years	Annual decline (p < 0.0001) in PF was found in the patients.
Egede, L.E. & Osborn, C.Y. (2008) (US) [23]	To evaluate the impact of depression on glycemic control and self-care.	Cross-sectional study	Internal medicine clinic	T2DM	N = 126 Mean age of the relevant group = 62.7 ± 11.8 years	Depression was negatively associated with social support (p = 0.002) and self-care activities (p = 0.004). Self-care of diabetes was partially associated with glycemic control (p = 0.08).
Gao, J. (2011) (China) [33]	To assess the impact of social support, self-efficacy, and self-care on glycemic control.	Cross-sectional study	Primary healthcare center	T2DM	N = 222 Age = 44–80 years	Self-care directly affected the glycemic control (p = 0.007); however, social support (p = 0.009), self-efficacy (p < 0.001), and PPC had an indirect effect on glycemic control.
Krein, S.L. (1998–1999) (US) [24]	Assessment of the association between chronic pain and diabetes self -management.	Cross-sectional study	Healthcare center	Not specified	N = 993 Age = 64 ± 10 years	Diabetes patients with chronic pain showed poor diabetes self-management and self-care (p = 0.002); similarly, those with severe or very severe chronic pain also reported poor self-management (p = 0.003) of diabetes.
Maraldi, C. (2001–2007) (US) [27]	Assessment of association between diabetes and depression.	Prospective cohort study	General community	Not specified	N = 2522 Age = 70–79 years	Diabetic patients had increased risk of depressed mood (p = 0.02) and recurrent depressed mood (p < 0.001) than non-diabetic patients.
Pijpers, E. (2009–2012) (Netherlands) [40]	Investigation of association between the risks of intermittent falls along with factors associated with it, and diabetes.	Longitudinal cohort study	General community	Not specified	N = 1145 Age ≥65 years	About 30% of the patients with diabetes had intermittent falls with an incidence rate of 129.7 per 1000 persons/year whereas, 19.4% of the subjects without diabetes had an incidence rate of intermittent falls recorded as 77.4 per 1000 persons/year HR = 1.67 (CI 95% = 1.11–2.51). Moreover, numerous physical and mental factors associated with diabetes, increased the risk of falls in diabetes patients by 47% HR = 1.3 (CI 95% = 0.79–2.11).
Schwartz, A.V. (1988–1994) (US) [25]	To assess the association between diabetes and risk of falls in older female diabetes patients.	Prospective cohort study	General community	Not specified	N = 9249 Age ≥ 67 years	Women with diabetes had more falls during follow-up (p <0.01). Diabetes and insulin use was associated with increased risk of falling among the patients i.e., more than once a year.
Sinclair, A.J. (2000) (UK) [31]	Assessment of linkage between impaired cognition self-care abilities among diabetes patients.	Case control study	General community	Not specified	N = 396 cases N = 393 controls Age ≥ 65 years	Diabetes patients having MMSE scores <23 had low levels of self-care (p < 0.001) and monitoring (p < 0.001). Association between low MMSE scores and higher hospitalization (p = 0.001), lower ADL (p < 0.001) and need of help in personal care (p = 0.001) was also seen.
Ulger, Z. (2002–2004) (Turkey) [38]	Assessment of malnutrition and factors associated with it in elderly.	Cross-sectional	Out-patient clinic	Not specified	N = 2327 Age ≥ 65 years	According to the results, 28% of the patients had poor MNA scores, which were mostly affected by depression (p = 0.0001), physical dependence (p = 0.0001), fasting plasma glucose level (p = 0.005), hematocrit (p = 0.005), ESR (p = 0.03), albumin (p = 0.002), bone mineral density (p = 0.007), and chronic diseases including diabetes (p = 0.820). The ratio of diabetes patients with and without the risk of malnutrition was 23.7%:24.2%.
Davies, M. (2006) (UK) [32]	Assessment of PDPN together with its severity and impact.	Cross-sectional descriptive study	General community	T2DM	N = 595 Mean age of relevant group = 67.1 ± 11.5 years	During the first phase of the study, 63.8% of the patients identified with pain. In the second phase, PDPN was found in about 19% of the patients. Furthermore, 36.8% of the patients suffered from non-neuropathic pain, and 7.4% of the patients had mixed pain. The prevalence of PDPN among the patients was 26.4%, and about 80% of those with PDPN reported moderate to severe pain, impairing their quality of life OR = 1.7 (CI 95% = 0.4–2.9%).
Galer, B.S. (1999) (US) [26]	Assessment of the nature and scope of PDN.	Cross-sectional study	Patients enrolled in a clinical trial	Not specified	N = 105 Age ≥ 60 years	Around 96% of the patients felt pain associated with neuropathy on their feet. Over half (53%) of the patients felt consistent pain which had become severe since the onset of PDN.
Thiel, D.M. (2011–2013) (Canada) [36]	To assess the association of compliance between physical activity recommendations and HRQoL in T2DM patients.	Prospective cohort study	Diabetes clinics, Public advertisement, primary care centers	T2DM	N = 1948 Mean Age = 64.5± 10.8 years	Results showed that 78.6% of the patients did not conform to the physical activity recommendations, while patients meeting the recommendations showed high scores of PF (p < 0.001), role physical (p = 0.001), body pain (p = 0.001), and physical component summary (p < 0.001) compared to the patients not meeting the required criteria.
Tabesh M. (2015) (Mauritius) [43]	Assessment of association between T2DM and physical functional disability. Moreover, determination of the degree of the association between related risk factors and diabetes.	Cross-sectional study	General community	T2DM	N = 3692 Mean Age = 62.1 ± 8.0	Diabetes was found to have significant association with increased risk of disability, OR = 1.76 (CI 95% = 1.34–2.08), among the study participants, having 13.2% of the prevalence of disability. Significant associations between diabetes and disability was seen among African Creoles OR = 2.03 (CI 95% = 1.16–3.56); whereas obesity highlighted the association between diabetes and disability, with an increased risk in South Asians and African Creoles of 26.3% and 12.1% respectively. The overall results showed a 67% increased risk of disability associated with diabetes.
Pai, Y.-W. (2013) (Taiwan) [42]	Assessment of the association between variation in fasting plasma glucose levels and PDPN among the T2DM patients.	Retrospective, case control study	Tertiary care hospital setting	T2DM	N = 2773 (enrolled) N = 626 (randomly selected from total) Age = 72.9 ± 10.5 years	The results showed that variation in fasting plasma glucose was significantly associated with PDPN OR = 4.08 (CI 95% = 1.60–10.42) in the third and fourth quartile, as compared to the first quartile OR = 5.49 (CI 95% = 2.14–14.06).
Yildirim, G.Z. (2014–2015) (Turkey) [39]	Assessment of nutritional status of the T2DM hospitalized patients, and highlighting the risk factors of malnutrition among such patients.	Cross-sectional study	Training and research hospital facility	T2DM	N = 104 Age = 65.08 ± 12.57	Results showed that the rate of malnutrition among the patients was 7.7%, whereas 18.3% patients were at risk of malnutrition. The risk factors of malnutrition among the patients were BMI <25 kg/m2, OR = 4.565 (CI 95% = 1.47–14.13), and duration of diabetes (15–20 years) OR = 5.535 (CI 95% = 1.15–26.6), (>20 years) OR = 7.147 (CI 95% = 1.59–31.96).
Tharek, Z. (2014–2015) (Malaysia) [44]	Assessment of the extent of self- efficacy, self-care behavior, and glycemic control and association between self-care behavior and glycemic control. Moreover, assessment of the factors associated with glycemic control among the T2DM patients.	Cross-sectional study	Primary Care Clinics	T2DM	N = 340 Age = 58.34 ± 11.86	Results showed the mean ± (SD) scores of self-efficacy 7.33 ± (2.25) and self-care behavior was 3.76 ± (1.87); whereas, a positive association existed between these factors r = 0.538 (p < 0.001). An inverse relation was found between self-efficacy and HbA1c, r = −0.41 (p < 0.001). Moreover, high self-efficacy has a significant association with good glycemic state, b = −0.398 (CI 95% = −0.024, −0.014), (p < 0.001)
Meneilly, G.S. (2015–2016) (Canada) [37]	Assessment of the status of management of T2DM of the elderly at the primary care clinics.	Cross-sectional study	Primary care clinics	T2DM	N = 833 Age ≥ 65 Years	Results showed that 53% participants had a HbA1c level ≤7%, the percentage of assessment for frailty, cognitive impairment, and depression was 11%, 16%, and 19% respectively; whereas, 88% and 83% assessments were of eye and foot examination respectively. Significant numbers of patients had cognitive impairment (p < 0.0001) and frailty (p < 0.0001), and a history of falls (p = 0.0007).
Aro, A.-K. (2015) (Finland) [45]	Assessment of HRQoL and the association between functional capability and glycemic control among the diabetes patients.	Cross-sectional study	Community-based study	Not specified	N = 172 Age > 65 Years	The EQ-5D scores for good glycemic control was 0.78, and for intermediate and poor glycemic control, it was 0.74 and 0.7 respectively (p = 0.037), HbA1c was significantly associated with poor HRQoL, r = 0.16 (CI95% = 0.01–0.31). Similarly, various domains of self-care (p = 0.031), mobility (p = 0.002), and IADL (p = 0.008) were compromised by poor glycemic control.
Fung, A.C.H. (2013) (China) [34]	Assessment of the association between depression and cardiac and metabolic risk factors, along with health condition among elderly T2DM patients.	Cross-sectional study	Diabetes center in a hospital setting	T2DM	N = 325 Age ≥ 65 Years	Depression was observed among 13% of the patients, with a positive history of co-morbidities OR = 2.84, (CI 95% = 1.35–6.00) (p = 0.006). The depressed patients had a longer duration of disease (mean disease duration ± (SD), 15.1 ± (9.1) versus 11.6 ± (8.1) years, (p = 0.02), a high frequency of hypoglycemic events (17 versus 6%) (p = 0.003), and poor target achievement (0 versus 16%) (p = 0.004).
Marden, J.R. (2006–2012) (USA) [28]	Assessment of association between diabetes, HbA1c and impaired memory among the patients with T2DM.	Prospective cohort Study Case control study (Little doubtful)	General community (noninstitutionalized population)	T2DM	N = 8888 Diabetics = 1837 Non Diabetics = 7051 Age = 67.4 ± 8.8	Diabetes was found to be significantly associated with a reduction of memory at a 10% faster rate (β = −0.04) per decade (CI 95% -0.06–0.01), an inverse relation was seen between HbA1c and memory loss with a 0.05 SD decline in memory score per decade (CI 95% = 0.08–0.03).

N = Sample size, GPA = General physical activities, LEM = lower extremity mobility, IADL = Instrumental activities of daily living, CVD = Cardiovascular diseases, PF = Physical functioning, DM = Diabetes mellitus, PB = Blood pressure, DSS = Digit symbol substitution, PPC = Patient provider communication, ADL = Activities of daily living, ESR = Erythrocyte sedimentation rate, PDPN = Painful diabetes-related peripheral neuropathy, PDN = Painful diabetes-related polyneuropathy, MNA = Mini nutritional assessment, HR = Hazard ratio, OR = Odd ratio, BI = Barthal index, CI = Confidence interval, CIB = Clock in box, CDT = Clock-drawing test, 3MS = Modified mini-mental state examination, MMSE=Mini-mental state examination, T1DM = Type 1 diabetes mellitus, DelRec = Delayed word-list recall, T2DM = Type 2 diabetes mellitus, BMI = Body mass index, HRQOL = Health-related quality of life.