Abstract: We included 21 randomised studies involving 1,690 caregivers; 19 studies compared telephone support interventions and usual care, of which 18 contributed data to the analyses. Two studies compared telephone and non-telephone professional support interventions. Caregiver ages ranged from 19 years to 87 years across studies. The majority of participants were female (> 70.53%), with two trials including females only. Most caregivers were family members, educated beyond secondary or high school level or had the equivalent in years of education. All caregivers were based in the community. Overall risk of bias was high for most studies. The results demonstrated that there is probably little or no difference between telephone support interventions and usual care for the primary outcome of quality of life at the end of intervention (SMD -0.02, 95% CI -0.24 to 0.19, 4 studies, 364 caregivers) (moderate-certainty evidence) or burden at the end of intervention (SMD -0.11, 95% CI -0.30 to 0.07, 9 studies, 788 caregivers) (low-certainty evidence). For one study where quality of life at the end of intervention was reported narratively, the findings indicated that a telephone support intervention may result in slightly higher quality of life, compared with usual care. Two further studies on caregiver burden were reported narratively; one reported that telephone support interventions may decrease burden, the other reported no change in the intervention group, compared with usual care. We are uncertain about the effects of telephone support interventions on caregiver depression at the end of intervention (SMD -0.37, 95% CI -0.70 to -0.05, 9 studies, 792 caregivers) due to very low-certainty evidence for this outcome. Depression was reported narratively for three studies. One reported that the intervention may reduce caregiver depression at the end of intervention, but this effect was not sustained at short-term follow-up. The other two studies reported there may be little or no difference between telephone support and usual care for depression at the end of intervention. Six studies measured satisfaction with the intervention but did not report comparative data. All six reported high satisfaction scores with the intervention. No adverse events, including suicide or suicide ideation, were measured or reported by any of the included studies. Our analysis indicated that caregiver anxiety may be slightly reduced (MD -6.0, 95% CI -11.68 to -0.32, 1 study, 61 caregivers) and preparedness to care slightly improved (SMD 0.37, 95% CI 0.09 to 0.64, 2 studies, 208 caregivers) at the end of intervention, following telephone-only support interventions compared to usual care. Findings indicated there may be little or no difference between telephone support interventions and usual care for all of the following outcomes at the end of intervention: problem-solving, social activity, caregiver competence, coping, stress, knowledge, physical health, self-efficacy, family functioning, and satisfaction with supports (practical or social). There may also be little or no effect of telephone support interventions for quality of life and burden at short-term follow-up or for burden and depression at medium-term follow-up. Litttle or no difference was found between groups for any of the reported outcomes in studies comparing telephone and non-telephone professional support interventions. We are uncertain as to the effects of telephone support interventions compared to non-telephone support interventions for caregiver burden and depression at the end of intervention. No study reported on quality of life or satisfaction with the intervention and no adverse events were reported or noted in the two studies reporting on this comparison. Although our review indicated slight benefit may exist for telephone support interventions on some outcomes (e.g. anxiety and preparedness to care at the end of intervention), for most outcomes, including the primary outcomes, telephone-only interventions may have little or no effect on caregiver outcomes compared to usual care. The findings of the review were mainly based on studies with overall high risk of bias, and few participants. Further high-quality trials, with larger sample sizes are required.

Plain-language summary: We included 21 studies involving 1,690 caregivers caring for persons with a range of diagnosed conditions. Caregiver ages ranged from 19 years to 87 years. Most were female and caring for a family member. The majority were spouses, in particular wives, except for one study that mainly focused on adult children. Most caregivers had greater than secondary school education. Eighteen studies reported funding from reputable sources. Key results Nineteen studies (18 studies contributing data) compared telephone support interventions and usual care. Telephone support interventions probably have little or no effect on caregiver quality of life (4 studies, 364 caregivers) and may have little effect on burden (9 studies, 788 caregivers) compared to usual care on completion of the intervention. Although anxiety may be slightly reduced and preparedness to care slightly improved following the intervention, we are uncertain about the effects on depression and overall, telephone interventions may have little or no effect on the outcomes assessed by this review. High satisfaction with the intervention was reported in six studies that measured this outcome, but no comparative data from usual care groups was reported. Two studies compared telephone and non-telephone-based support interventions. There may be little or no evidence of an effect of telephone support when compared non-telephone-based support interventions for any reported outcome. No adverse events were measured or reported in any of the included studies. Quality of evidence The quality of the evidence was assessed as very low to moderate across outcomes, thus reducing confidence in the findings. Many of the results were based on data from single studies with few participants. Larger well-designed studies are required to determine the effects of telephone support interventions.