1.1 The Burden of Proof

Science is a beautiful thing. It is a landscape of exploration and one that at its root is tasked with finding evidence, and establishing cause and effect. At a fundamental level, this implies that science should be able to answer questions like these

If I exercise daily, how is this likely to affect my cardiovascular health?

If we build a road here, how will the local population of bighorn sheep be affected?

As you'll discover throughout your degree, scientists tackle such questions through a combination of exploratory research and confirmatory research. At the exploratory stage, ideas are generated and associations are discovered. Exploratory research gives rise to hypotheses that can then be tested through confirmatory research, which requires well-designed experiments. For instance, based on observation, we have long hypothesized that there are positive associations between exercise and physical health. But establishing that daily exercise causes healthy outcomes is a different challenge.

Exploratory research gives rise to hypotheses that can then be tested through confirmatory research, which requires well-designed experiments.

Many research teams have designed studies to address various aspects of these observed benefits of physical activity. One such team, an interdisciplinary research team at UBC, tackled this question in relation to falls in an aging population. The researchers designed an experiment to to test whether strength training after experiencing a fall in an aging population would reduce injuries from a subsequent fall.

Exercise and Positive Health Outcomes

After reading the following abstract from Liu-Ambrose et al's paper Effect of a Home-Based Exercise Program on Subsequent Falls Among Community-Dwelling High-Risk Older Adults After a Fall, try and answer the following questions.

Was this study confirmatory or exploratory? How do we know this?
Who participated in the study?
What was the intervention?
What were the main conclusions?

Abstract

Importance Whether exercise reduces subsequent falls in high-risk older adults who have already experienced a fall is unknown.

Objective To assess the effect of a home-based exercise program as a fall prevention strategy in older adults who were referred to a fall prevention clinic after an index fall.

Design, Setting, and Participants A 12-month, single-blind, randomized clinical trial conducted from April 22, 2009, to June 5, 2018, among adults aged at least 70 years who had a fall within the past 12 months and were recruited from a fall prevention clinic.

Interventions Participants were randomized to receive usual care plus a home-based strength and balance retraining exercise program delivered by a physical therapist (intervention group; n = 173) or usual care, consisting of fall prevention care provided by a geriatrician (usual care group; n = 172). Both were provided for 12 months.

Main Outcomes and Measures The primary outcome was self-reported number of falls over 12 months. Adverse event data were collected in the exercise group only and consisted of falls, injuries, or muscle soreness related to the exercise intervention.

Results Among 345 randomized patients (mean age, 81.6 [SD, 6.1] years; 67% women), 296 (86%) completed the trial. During a mean follow-up of 338 (SD, 81) days, a total of 236 falls occurred among 172 participants in the exercise group vs 366 falls among 172 participants in the usual care group. Estimated incidence rates of falls per person-year were 1.4 (95% CI, 0.1-2.0) vs 2.1 (95% CI, 0.1-3.2), respectively. The absolute difference in fall incidence was 0.74 (95% CI, 0.04-1.78; P = .006) falls per person-year and the incident rate ratio was 0.64 (95% CI, 0.46-0.90; P = .009). No adverse events related to the intervention were reported.

Conclusions and Relevance Among older adults receiving care at a fall prevention clinic after a fall, a home-based strength and balance retraining exercise program significantly reduced the rate of subsequent falls compared with usual care provided by a geriatrician. These findings support the use of this home-based exercise program for secondary fall prevention but require replication in other clinical settings.

Trial Registration ClinicalTrials.gov Identifiers: NCT01029171; NCT00323596

Causal Links

Suggesting a causal link brings with it the need to show your proof. This burden of scientific proof requires both creativity and rigour; studies must be well designed and well executed. It also requires that studies be independently replicated to show that, if repeated, they will result in the same conclusions, reinforcing the validity of the original findings. On the other hand, a replication study may come to a different conclusion, potentially invalidating the conclusions of the original study.

Say, for example, that you're provided with the choice between two medications to treat a medical condition - we'll leave the details of this medical condition up to your imagination. Neither has a record of adverse side effects, but one drug, we'll be creative and call it "drug A" has findings obtained from only a single research lab, while "drug B" underwent five independently replicated studies in five different labs with five independent researchers. Which medication might you choose?